Jump to content
dreifish

How to: 52000 lumens neutrally-bouyant GH5 rig

Recommended Posts

Posted (edited)

Lately, I've been using 2 Gates GT14 14k lumen lights + 2 ScubaLamp V6K 12000 lumens lights (and I wish I had about twice that much light, still).

 

Needless to say, the lights are quite heavy. Given that the Nauticam GH5 housing is already negative, that means significant additional floatation is needed to get the whole rig neutral (which is how I like to keep it for wide angle video.)

 

Here's what I've come up with:

 

 

 

post-42872-0-34160200-1546394744_thumb.jpg

 

post-42872-0-70673300-1546404878_thumb.jpg

 

Unfortunately, it's very heavy on land, and the arms have a tendency to swing loose even with the clamps tightened down all the way, which makes transporting it a hastle. In the water, it's pretty good, but still has a lot of mass. We need some lighter LED lights!

post-42872-0-21949100-1546397316_thumb.jpg

Edited by dreifish
  • Like 1

Share this post


Link to post
Share on other sites

Very impressive..! Wow!

 

I would look at replacing the clamp arms with loctight nuts and wrenching them down really tight - and bridging the gap between the two V6K’s to give even more strength.

 

These clamps aren’t great are they for heavy stuff :-(

 

The other thing would be to looking at the really big jumbo arms from Nauticam the 90x200 (I think) and replacing some of the smaller foam ones

Share this post


Link to post
Share on other sites

Wow you could literally fry some fish

 

I would challenge the use of 4 lights actually as they are too close to each other to really provide benefit and they will never match your WWL

 

I think if you can live with 3 lights you can get rid of all the clamps on the top use a triple to connect the side lights and build a triangle with two short mega arm to join with another triple and connect a single light.

Your lights have 120 degrees and 90 so am not sure it makes sense to put the narrower ones on the sides? I would try with a single gates in the middle (as the centre is what you care the most) and the other two on the sides. This would also give you the option to keep the light float on and you would definitely get rid of the entire bottom part

Share this post


Link to post
Share on other sites

You're right that three lights would be fine in terms of coverage, Interceptor (even two is ok with good positioning, though the GT14s have a dead spot in the middle configured as shown -- I'd have to move them in closer.)

 

The reason I use 4 is purely for the light output. Ideally, I'd replace the whole lot with 4 24k lumen lights if light output was the only consideration. Right now, I can only shoot at F5.6-1/125-ISO200 and still properly light things. I'd like the option to get nice colors even when I have to close down to F8-1/125/ISO200 or F5.6-1/250-ISO200 to better match ambient light conditions between 10am and 3pm in clear water.

 

Yeah, there's no reason to keep the V6Ks in the middle since they have wider coverage. But I usually only turn the V6Ks on if (a) I'm filming something closer than .3m to avoid the dead-spot of the GT14s (too lazy to reconfigure the arms) or (b) I need the sheer light output.

 

I actually reassembled the whole thing this afternoon to get rid of the 4 bottom floats since they had a tendency to try to pull the whole rig upside-down. I moved two of the 8-inch ultralight arms with 3 stix floats each up to create a joint on each side, and then one V6K + one GT14 at the end of each articulated arm. I zip-tied two stix floats to each V6K to fine-tune the buoyancy. So the whole rig is a little lighter now and doesn't try to turn upside down anymore, but it's still a lot of weight on the extended ball at either end of the nauticam carbon fiber float.

 

Trickster, what are these loctight nuts you mentioned? I'm intrigued.

Share this post


Link to post
Share on other sites
Posted (edited)

Trickster, what are these loctight nuts you mentioned? I'm intrigued.

 

I replaced the bolts with the same style, but 10mm shorter and replaced the turning handle part (sorry, not sure on the right name!) with a loctight nut on the pieces where I won't be moving or adjusting them:

 

post-43742-0-48435400-1546434369_thumb.jpg

 

The nuts are the ones with the rubber/plastic gasket inside, any local hardware store would have them in either A2 or A4 (316)

Edited by thetrickster
  • Like 1

Share this post


Link to post
Share on other sites

This is a pretty impressive project. Kudos for sharing your innovative setup and for all the great suggestions from others. I am curious to know how you pack this all down for travel. How much of this can you get into carry-on versus checked luggage? Or, do you go with a reduced setup when flying?

Share this post


Link to post
Share on other sites

Keldan Luna all the life.

 

They are nearly neutral underwater.

Share this post


Link to post
Share on other sites

For the clamps that are normally fixed or non-adjustable under water, use the lock nuts recommended previously, but remove the 'O' rings for better metal to metal clamping friction.

 

To facilitate under water mobility, hire an under water porter :laugh:

Share this post


Link to post
Share on other sites
Posted (edited)

This is a pretty impressive project. Kudos for sharing your innovative setup and for all the great suggestions from others. I am curious to know how you pack this all down for travel. How much of this can you get into carry-on versus checked luggage? Or, do you go with a reduced setup when flying?

 

So, believe it or not, I've managed to cram all of that (less the V6K lights) plus two YS-D2 strobes in in a Thinktank backpack (the largest domestic carry-on size one). I've removed most of the dividers so it's a bit of a jumble in there, but it works. I usually carry on the ultralight arms and clamps but check in the Stix floats though. Haven't travelled much with it recently though, so we'll see if that still works with the new roller I bought end of the month. Um.. it's never been weighed (knock on wood).

 

Keldan Luna all the life.

 

They are nearly neutral underwater.

 

True, Davide. That would help some, but the weight is pretty comprable, so still a pain in the ass outside water. In water, my setup is neutral, so it's less of a hassle.

 

 

I replaced the bolts with the same style, but 10mm shorter and replaced the turning handle part (sorry, not sure on the right name!) with a loctight nut on the pieces where I won't be moving or adjusting them:

 

attachicon.gifIMG_0381.jpg

 

The nuts are the ones with the rubber/plastic gasket inside, any local hardware store would have them in either A2 or A4 (316)

 

Great idea, thanks. I guess I could do that for the clamps that hold the cross-bar float in place.

 

For the clamps that are normally fixed or non-adjustable under water, use the lock nuts recommended previously, but remove the 'O' rings for better metal to metal clamping friction.

 

To facilitate under water mobility, hire an under water porter :laugh:

 

Hahaha.. well, I got a DPV to handle that part. Sadly I flooded it last month, so I'm getting more exercise these days...

 

 

Here is the new setup:

 

post-42872-0-45943000-1546502282_thumb.jpg

Edited by dreifish
  • Like 2

Share this post


Link to post
Share on other sites

You're right that three lights would be fine in terms of coverage, Interceptor (even two is ok with good positioning, though the GT14s have a dead spot in the middle configured as shown -- I'd have to move them in closer.)

 

The reason I use 4 is purely for the light output. Ideally, I'd replace the whole lot with 4 24k lumen lights if light output was the only consideration. Right now, I can only shoot at F5.6-1/125-ISO200 and still properly light things. I'd like the option to get nice colors even when I have to close down to F8-1/125/ISO200 or F5.6-1/250-ISO200 to better match ambient light conditions between 10am and 3pm in clear water.

 

Yeah, there's no reason to keep the V6Ks in the middle since they have wider coverage. But I usually only turn the V6Ks on if (a) I'm filming something closer than .3m to avoid the dead-spot of the GT14s (too lazy to reconfigure the arms) or (b) I need the sheer light output.

 

I actually reassembled the whole thing this afternoon to get rid of the 4 bottom floats since they had a tendency to try to pull the whole rig upside-down. I moved two of the 8-inch ultralight arms with 3 stix floats each up to create a joint on each side, and then one V6K + one GT14 at the end of each articulated arm. I zip-tied two stix floats to each V6K to fine-tune the buoyancy. So the whole rig is a little lighter now and doesn't try to turn upside down anymore, but it's still a lot of weight on the extended ball at either end of the nauticam carbon fiber float.

 

Trickster, what are these loctight nuts you mentioned? I'm intrigued.

Bit confused :lol2:

The WWL is 130 deg with a 28mm FF equivalent lens your GT14s being 90 each should easily cover that. What am I missing?

Stix floats are ok as long as you are shallow when you go deeper they compress and loose buoyancy.

Why not go up to ISO 400 ? Its GH5 native ISO so in theory you get the best image quality and dynamic range from the sensor.

If you are less the 0.3m aren't you blowing highlights with all these light? I understand you step down the lens to set the exposure (since you cant go much lower than ISO 200 and setting the shutter higher might create other issues if there is lots of motion in the scene) doesnt that create diffraction problems? Are you shooting against the sun and try to protect the highlights and get nice blues when filming? With the sun behind you, you got plenty of light between 10am and 3pm in tropical clear water, if deeper then you don't compete with the sun and your lights have a greater effect anyway. Just trying to understand why so much light is needed.

Thanks for taking the time :beer:

Share this post


Link to post
Share on other sites

Bit confused :lol2:

The WWL is 130 deg with a 28mm FF equivalent lens your GT14s being 90 each should easily cover that. What am I missing?

Stix floats are ok as long as you are shallow when you go deeper they compress and loose buoyancy.

Why not go up to ISO 400 ? Its GH5 native ISO so in theory you get the best image quality and dynamic range from the sensor.

If you are less the 0.3m aren't you blowing highlights with all these light? I understand you step down the lens to set the exposure (since you cant go much lower than ISO 200 and setting the shutter higher might create other issues if there is lots of motion in the scene) doesnt that create diffraction problems? Are you shooting against the sun and try to protect the highlights and get nice blues when filming? With the sun behind you, you got plenty of light between 10am and 3pm in tropical clear water, if deeper then you don't compete with the sun and your lights have a greater effect anyway. Just trying to understand why so much light is needed.

Thanks for taking the time :beer:

 

Very interesting comments

 

With two 90 degrees light the area properly exposed without shadows is the intersection of the two light cones which is something like a paraboloic shape that at best is 90 degrees wide

 

The area not interesecting will be exposed by a single light and have shadow on the other side or not exposed at all

Makes sense??

 

This is the reason why coverage of a strobe should exceed angle of view of the lens example macro

If it doesnt make sense take your lights on a tray in a dark room and look at the wall you can see the frame will have dark areas

 

 

The op is not shooting vlog so his base ISO is 200 and can even go to 100 if he wishes. I use cinelike 200 and when too shallow I set to 100

Share this post


Link to post
Share on other sites

Also re stix compression they dont

Closed cell polythene has a tensile strength of 1952 kpa which means the float are likely to break at 190 meters. At 30-40 meters they dont even feel it

The only issue with stix float is that they dont come bigger than the 160g lift jumbo

Share this post


Link to post
Share on other sites

Below 50 meters Stix become like chewed marshmallow. I tried them many times. You need a much dens closed cell foam like thalagal or equivalent.

But of course it's not a op requirement

  • Like 2

Share this post


Link to post
Share on other sites

Below 50 meters Stix become like chewed marshmallow. I tried them many times. You need a much dens closed cell foam like thalagal or equivalent.

But of course it's not a op requirement

Maybe stix do no use divinycell however I have not noticed heavy compression at 30 meters but I have not been at 60 meters either

 

Either way if you dive with wetlenses and therefore the weight of your rig is fixed as you always have a flat port float arms may make more sense. At normal depth 0-25m for video there is technical compression benefit between a float arm and a float mounted on a standard arm in my experience

 

 

So, believe it or not, I've managed to cram all of that (less the V6K lights) plus two YS-D2 strobes in in a Thinktank backpack (the largest domestic carry-on size one). I've removed most of the dividers so it's a bit of a jumble in there, but it works. I usually carry on the ultralight arms and clamps but check in the Stix floats though. Haven't travelled much with it recently though, so we'll see if that still works with the new roller I bought end of the month. Um.. it's never been weighed (knock on wood).

 

 

True, Davide. That would help some, but the weight is pretty comprable, so still a pain in the ass outside water. In water, my setup is neutral, so it's less of a hassle.

 

 

Great idea, thanks. I guess I could do that for the clamps that hold the cross-bar float in place.

 

 

Hahaha.. well, I got a DPV to handle that part. Sadly I flooded it last month, so I'm getting more exercise these days...

 

 

Here is the new setup:

 

attachicon.gifIMG_20190103_065028_BURST002.jpg

Looks better if you wanted to get rid of the floats you could replace them all with a 90x200 carbon arm or an Inon mega float M

 

You still would not eliminate the floats on the gates but your set up would be around 120-130 grams lighter in water

  • Like 1

Share this post


Link to post
Share on other sites

Bit confused :lol2:

The WWL is 130 deg with a 28mm FF equivalent lens your GT14s being 90 each should easily cover that. What am I missing?

Stix floats are ok as long as you are shallow when you go deeper they compress and loose buoyancy.

Why not go up to ISO 400 ? Its GH5 native ISO so in theory you get the best image quality and dynamic range from the sensor.

If you are less the 0.3m aren't you blowing highlights with all these light? I understand you step down the lens to set the exposure (since you cant go much lower than ISO 200 and setting the shutter higher might create other issues if there is lots of motion in the scene) doesnt that create diffraction problems? Are you shooting against the sun and try to protect the highlights and get nice blues when filming? With the sun behind you, you got plenty of light between 10am and 3pm in tropical clear water, if deeper then you don't compete with the sun and your lights have a greater effect anyway. Just trying to understand why so much light is needed.

Thanks for taking the time :beer:

 

The GT14s are indeed 90 degrees each, which means the beams converge about an equal distance in front of the lights as the distance between the two. So, if the lights are 50cm apart, the beams would converge about 50cm in front of the lights. Because of the handles of the housing, it's basically impossible to move 2 side-mounted lights closer than around 20-30cm apart. Since I sometimes film subjects as close as 5-10cm from the front of the lens, this can create a dead spot in the center of the image where neither light illuminates. That's where a third top-mounted light would be helpful sometimes. Of course, I could also just turn the lights inward a bit for these sort of situations.

 

Stix floats do compress slightly starting around 20-30m, but the loss of bouyancy in recreational depths is minor. I estimate my rig is maybe 50-100g less bouyant at 40m than at the surface. Not enough to alter it's characteristics significantly. I wouldn't use them for 60+m dives though, for sure.

 

This 'native iso' business is a bit misleading. It's true that the Panasonic rates the base exposure for VLOG at ISO400, but this is to reflect the fact that when shooting VLOG you're basically lifting the shadows a bit to increase dynamic range, so by rating the camera at ISO400, you close down the aperture/shutter to compensate for the exposure, protecting the highlights in the process and maximizing dynamic range. The tradeoff is that you create more noise in the shadows.

 

I rarely shoot in vlog underwater, because it's not a high contrast environment. Particles in the water defract light, creating more even illumination. Add to that the fact that I'm usually using video lights to fill in the shadows and we're not dealing with scenes that contain a large dynamic range anymore.

 

Also, in terms of stills, the GH5 has the highest dynamic range at ISO200 (which is what the sensor is rated at without any additional analog or digital gain). Check DxOMark. ISO100 is an 'extended ISO' setting. Basically, the camera is still using the ISO200 (0db) signal, but actually pulling down the whole image one stop. You don't get any additional dynamic range (in fact, you lose some since you're crushing the shadows) but you are reducing noise somewhat. Nothing wrong with shooting at ISO100 when you need to reduce exposure, but keep in mind you're not actually increasing your dynamic range.

 

In practice, I keep my aperture between F3.5 and F8 to avoid diffraction, and rarely go to F11. Iso ranges between 200-800 most of the time. Shutter speed 1/125 most of the time since I'm filming 60p, but I will sometimes step down to 1/250 if the ambient exposure is really bright (or when filming sun rays because it helps separate the sun rays from each other a bit more). I never noticed 1/250 producing jagged motion, but I think that's to taste. I sometimes also shoot 1/100 shutter speed for 24p for drone shots and prefer the extra sharpness. I think weird motion blur from shooting something other than 1/2x frame rate is most noticeable when your main subject is a human in (fast) motion, which isn't the majority of my shots.

 

As I mentioned, with 52k lumens of video lights, I find that F5.6-1/125-ISO200 is the proper exposure for wide angle scenes (discounting ambient light levels - so for example, if shooting wide angle in a cave or at night). Nothing gets blown out. For macro, I might step down a couple of stops to F8 or F11 to avoid overexposure, which is exactly where you want to be for macro anyway for the increased depth of field. The problem arises when the ambient light is too bright for an F5.6-1/125-ISO200 exposure. In those circumstances, I have to shut down the aperture further or go to ISO100 to avoid the ambient light over-exposing the scene. But once you do that, the impact of your artificial lights is lessened, and you no longer get vibrant reds/oranges/yellows. You can partially compensate with a warmer white balance, but I'd prefer to have stronger lights and keep the white balance at 5000-5500k to get a pleasing blue color in the water column. Hence the desire to double my light power :)

  • Like 3

Share this post


Link to post
Share on other sites
Posted (edited)

Very interesting comments

 

With two 90 degrees light the area properly exposed without shadows is the intersection of the two light cones which is something like a paraboloic shape that at best is 90 degrees wide

 

The area not interesecting will be exposed by a single light and have shadow on the other side or not exposed at all

Makes sense??

 

This is the reason why coverage of a strobe should exceed angle of view of the lens example macro

If it doesnt make sense take your lights on a tray in a dark room and look at the wall you can see the frame will have dark areas

 

 

The op is not shooting vlog so his base ISO is 200 and can even go to 100 if he wishes. I use cinelike 200 and when too shallow I set to 100

Interceptor you are more confused than i am or my way of writing doesn't help you understand what i mean :lol2:

If you are too close to your subject so that it fells in the dark spot in front of you camera move the lights inwards it will do the trick. Put your lights in a tray and try in a pool changing your distance to the subject and moving the lights to accommodate. UW photography masterclass by Alex Mustard is also an excellent read to understand the concept.

I wasn't talking Vlog. You are confusing base ISO with native ISO. Native ISO on the GH5 is 400 according to Panasonic.

Re Stix floats they compress even at recreational depths, they compress even more if you "crush"them ones to deeper depths (60-70m) after that they compress more and shallower than before.

Edited by Lionfi2s

Share this post


Link to post
Share on other sites

 

The GT14s are indeed 90 degrees each, which means the beams converge about an equal distance in front of the lights as the distance between the two. So, if the lights are 50cm apart, the beams would converge about 50cm in front of the lights. Because of the handles of the housing, it's basically impossible to move 2 side-mounted lights closer than around 20-30cm apart. Since I sometimes film subjects as close as 5-10cm from the front of the lens, this can create a dead spot in the center of the image where neither light illuminates. That's where a third top-mounted light would be helpful sometimes. Of course, I could also just turn the lights inward a bit for these sort of situations.

 

Stix floats do compress slightly starting around 20-30m, but the loss of bouyancy in recreational depths is minor. I estimate my rig is maybe 50-100g less bouyant at 40m than at the surface. Not enough to alter it's characteristics significantly. I wouldn't use them for 60+m dives though, for sure.

 

This 'native iso' business is a bit misleading. It's true that the Panasonic rates the base exposure for VLOG at ISO400, but this is to reflect the fact that when shooting VLOG you're basically lifting the shadows a bit to increase dynamic range, so by rating the camera at ISO400, you close down the aperture/shutter to compensate for the exposure, protecting the highlights in the process and maximizing dynamic range. The tradeoff is that you create more noise in the shadows.

 

I rarely shoot in vlog underwater, because it's not a high contrast environment. Particles in the water defract light, creating more even illumination. Add to that the fact that I'm usually using video lights to fill in the shadows and we're not dealing with scenes that contain a large dynamic range anymore.

 

Also, in terms of stills, the GH5 has the highest dynamic range at ISO200 (which is what the sensor is rated at without any additional analog or digital gain). Check DxOMark. ISO100 is an 'extended ISO' setting. Basically, the camera is still using the ISO200 (0db) signal, but actually pulling down the whole image one stop. You don't get any additional dynamic range (in fact, you lose some since you're crushing the shadows) but you are reducing noise somewhat. Nothing wrong with shooting at ISO100 when you need to reduce exposure, but keep in mind you're not actually increasing your dynamic range.

 

In practice, I keep my aperture between F3.5 and F8 to avoid diffraction, and rarely go to F11. Iso ranges between 200-800 most of the time. Shutter speed 1/125 most of the time since I'm filming 60p, but I will sometimes step down to 1/250 if the ambient exposure is really bright (or when filming sun rays because it helps separate the sun rays from each other a bit more). I never noticed 1/250 producing jagged motion, but I think that's to taste. I sometimes also shoot 1/100 shutter speed for 24p for drone shots and prefer the extra sharpness. I think weird motion blur from shooting something other than 1/2x frame rate is most noticeable when your main subject is a human in (fast) motion, which isn't the majority of my shots.

 

As I mentioned, with 52k lumens of video lights, I find that F5.6-1/125-ISO200 is the proper exposure for wide angle scenes (discounting ambient light levels - so for example, if shooting wide angle in a cave or at night). Nothing gets blown out. For macro, I might step down a couple of stops to F8 or F11 to avoid overexposure, which is exactly where you want to be for macro anyway for the increased depth of field. The problem arises when the ambient light is too bright for an F5.6-1/125-ISO200 exposure. In those circumstances, I have to shut down the aperture further or go to ISO100 to avoid the ambient light over-exposing the scene. But once you do that, the impact of your artificial lights is lessened, and you no longer get vibrant reds/oranges/yellows. You can partially compensate with a warmer white balance, but I'd prefer to have stronger lights and keep the white balance at 5000-5500k to get a pleasing blue color in the water column. Hence the desire to double my light power :)

Thanks Andrei! Hope you understand that i am asking to discuss and learn and not to critique :beer:

Panasonic states that the native ISO for the GH5 is 400. Dxo numbers are different anyway (eg ISO 100 on the camera corresponds to their ISO 64 if I remember correctly). Most users experiences also agree that ISO 400 they get the best results in terms of dynamic range, color and noise. I am not a pixel peeper so I cant tell. My thinking is that if you work at ISO 400 as a base you still got room to move down the range to ISO 200 if needed and still got very good results.

I understand the third light concept to cover something very close to your port and not wanting to move the lights in but does it have to be so bright since you will be so close?

I understand the reason for wanting to keep the specific exposure settings when it comes to maintaining the quality of the blue color. What IRE are you placing your blues at?

Agreed Vlog is not really needed underwater but its the only way (with the exception of HLG) to produce HDR content (which i think based on your footage you should :good:)

Thanks again for taking the time and for your always informative posts!

Share this post


Link to post
Share on other sites

My thinking is that if you work at ISO 400 as a base you still got room to move down the range to ISO 200 if needed and still got very good results.

 

Not to go off on a tangent...

 

The native ISO (the one where the SNR has been optimised) for the GH5 and GH5s (in Auto or Low mode) is ISO400 - which is where you will get 11-13stops, depending who you speak too.

 

If you set the camera to show SS/Gain instead of ISO, you will find that 0 Db is equivalent to ISO400. Changing the gain either + or - you will lose dynamic range, so ideally you want to fix that and either play with lighting or aperture.

 

As Dreifish mentions - ambient light is still bright! the last dive I did over Christmas period, I was shocked how much ambient light there was, as I was running the camera at C4K@30, 1/60, 0Db - and was having to go to f8/f11 to get correct exposure on my waveforms.

  • Like 1

Share this post


Link to post
Share on other sites

 

Not to go off on a tangent...

 

The native ISO (the one where the SNR has been optimised) for the GH5 and GH5s (in Auto or Low mode) is ISO400 - which is where you will get 11-13stops, depending who you speak too.

 

If you set the camera to show SS/Gain instead of ISO, you will find that 0 Db is equivalent to ISO400. Changing the gain either + or - you will lose dynamic range, so ideally you want to fix that and either play with lighting or aperture.

 

As Dreifish mentions - ambient light is still bright! the last dive I did over Christmas period, I was shocked how much ambient light there was, as I was running the camera at C4K@30, 1/60, 0Db - and was having to go to f8/f11 to get correct exposure on my waveforms.

That is exactly what i am saying too Richard when saying that native ISO on the GH5 is 400.

Share this post


Link to post
Share on other sites

There is no concept of native ISO a camera has a base ISO that depends on the gamma curve in use

For linear curves that include all normal modes for still pictures and cinelike mode the base ISO is 200.

For logarithmic curves that include VLOG and HLG the base ISO is 400 you cannot go lower.

If you set a minimum ISO of 400 on a normal gamma curve using profiles like natural or cinelike you are increasing noise and in turn decreasing colour depth and dynamic range

 

For what concerns the gain indicator dB and stops are on different scales the situation is quite weird and there is definitely something going on. When you set a log profile the two scales match 400 800 1600 ISO corresponds to 0 3 6 dB. When you set a linear profile the ISO goes 200 400 800 and the gain goes -6 -3 0 suggesting that 0dB is ISO 800 so I believe there is a bit of bug there when you use extended ISO -12 dB appears. I would completely ignore this gain display as clearly it has issues except in LOG.

 

In practical circumstances I found that cinelike D with leeming LUT is very useful shooting 10 bit 400 mbps. In situation of bright scenes you can force the camera to ISO 100 this is basically putting an attenuator on the circuit that will give you 1 stop for wider aperture or slower shutter speed so that you get the effect you like. I did some snorkelling in Marsa Alam and I used ISO 100 at the surface with 24p mode and 1/100 shutter speed and the camera stayed below f/13 which is what I wanted. I still occasionally got some clipped highlights (see example here https://youtu.be/T7E9g0z6F0U?t=201)

but overall I was quite happy, by the way skin diving with a video set up is deadly and you just can't get exposure right...

Share this post


Link to post
Share on other sites

There is no concept of native ISO a camera has a base ISO that depends on the gamma curve in use

For linear curves that include all normal modes for still pictures and cinelike mode the base ISO is 200.

For logarithmic curves that include VLOG and HLG the base ISO is 400 you cannot go lower.

If you set a minimum ISO of 400 on a normal gamma curve using profiles like natural or cinelike you are increasing noise and in turn decreasing colour depth and dynamic range

 

For what concerns the gain indicator dB and stops are on different scales the situation is quite weird and there is definitely something going on. When you set a log profile the two scales match 400 800 1600 ISO corresponds to 0 3 6 dB. When you set a linear profile the ISO goes 200 400 800 and the gain goes -6 -3 0 suggesting that 0dB is ISO 800 so I believe there is a bit of bug there when you use extended ISO -12 dB appears. I would completely ignore this gain display as clearly it has issues except in LOG.

 

In practical circumstances I found that cinelike D with leeming LUT is very useful shooting 10 bit 400 mbps. In situation of bright scenes you can force the camera to ISO 100 this is basically putting an attenuator on the circuit that will give you 1 stop for wider aperture or slower shutter speed so that you get the effect you like. I did some snorkelling in Marsa Alam and I used ISO 100 at the surface with 24p mode and 1/100 shutter speed and the camera stayed below f/13 which is what I wanted. I still occasionally got some clipped highlights (see example here https://youtu.be/T7E9g0z6F0U?t=201)

but overall I was quite happy, by the way skin diving with a video set up is deadly and you just can't get exposure right...

 

This is basically my understanding as well. I need to find a good article that covers the technical discussion, but in a nutshell, there's no direct relationship between the signal of the CMOS sensor and the ISO. For video, ISO is influenced by the gamma curve of the picture profile used -- ISO 400 in VLOG and ISO 400 in d-cinelike/standard don't produce the same exposure. Changing the ISO doesn't impact the signal from the CMOS sensor, just how the camera processes that signal into the video file. One (somewhat sloppy) way to think of it is that your ISO is a tradeoff between dynamic range, noise, and the distribution of usable dynamic range above and below middle gray. In VLOG, the GH5 can record about 11.5 stops of dynamic range at ISO 400. Go to ISO 800, and your overall dynamic range will decrease to 11 stops or so, BUT you'll get more of that range allocated to the highlights. So, somewhat counter-intuitively, higher ISOs actually protect the highlights a little better. Conversely, if you could shoot VLOG at ISO 200, you'd also lose a bit of dynamic range, but your shadows would be cleaner, so you'd get more of the remaining dynamic range allocated to the shadow regions.

 

When shooting in d-cinelike/standard however, the gamma curve of the picture profile itself will never allow you to record more than 9-10 stops of dynamic range. So whether you shoot at ISO 200, 400 or 800, your dynamic range is going to more or less be maxed in those profiles anyway. The only difference is that you'll get (slightly) less noise at the lower ISOs. Personally, I find almost no perceptable difference in the footage in terms of either dynamic range or noise in the ISO 100-800 range. So I just use whatever the exposure dictates.

 

 

Not to go off on a tangent...

 

The native ISO (the one where the SNR has been optimised) for the GH5 and GH5s (in Auto or Low mode) is ISO400 - which is where you will get 11-13stops, depending who you speak too.

 

If you set the camera to show SS/Gain instead of ISO, you will find that 0 Db is equivalent to ISO400. Changing the gain either + or - you will lose dynamic range, so ideally you want to fix that and either play with lighting or aperture.

 

As Dreifish mentions - ambient light is still bright! the last dive I did over Christmas period, I was shocked how much ambient light there was, as I was running the camera at C4K@30, 1/60, 0Db - and was having to go to f8/f11 to get correct exposure on my waveforms.

 

Yeah, the ambient light (especially in the tropics) is a big issue for trying to shoot blended-light exposures. Shooting at 60p (and 1/125 shutter speed) helps to keep your aperture around F5.6, which is optimal on a m4/3 sensor to minimize diffraction. I try to avoid F11 unless I really need the increased depth of field for macro (or with a rectilinear wide angle zoom in a dome port). That's why I'm always a little confused when people focus so much on a camera's low-light performance. Maybe they shoot in very different environments than I do. I almost never have to raise my ISO above 800 :).

 

Thanks Andrei! Hope you understand that i am asking to discuss and learn and not to critique :beer:

Panasonic states that the native ISO for the GH5 is 400. Dxo numbers are different anyway (eg ISO 100 on the camera corresponds to their ISO 64 if I remember correctly). Most users experiences also agree that ISO 400 they get the best results in terms of dynamic range, color and noise. I am not a pixel peeper so I cant tell. My thinking is that if you work at ISO 400 as a base you still got room to move down the range to ISO 200 if needed and still got very good results.

I understand the third light concept to cover something very close to your port and not wanting to move the lights in but does it have to be so bright since you will be so close?

I understand the reason for wanting to keep the specific exposure settings when it comes to maintaining the quality of the blue color. What IRE are you placing your blues at?

Agreed Vlog is not really needed underwater but its the only way (with the exception of HLG) to produce HDR content (which i think based on your footage you should :good:)

Thanks again for taking the time and for your always informative posts!

I rarely (never) find myself wishing I had less artificial light. Usually the opposite. But yes, technically, if you only use the middle light for situations when you're filming something very close to the lens, it could be weaker. Seeing as I'm usually starved for (artificial) light, I end up turning all my lights on all the time.

 

The question about the IRE of the water column is an interesting one. I haven't thought about it before.. I usually expose/grade by eye, going for a strong color contrast between warm subjects and blue water column. Looking at my past footage, it seems I like to expose the water column around 25IRE, sometimes a little lower. Almost never above 50IRE. Very curious to hear what other people do.

 

HDR footage is a whole other topic. In short, I'd like to produce it, but have too many limitations/compromises with my current gear. The biggest is that I don't have an HDR monitor for grading or an HDR display, so can't verify the results. Other minor issues: (a) no option for shooting in HDR and 60p on the GH5, and I favor 60p usually; (b) the 10bit 400mb/s All-I files add up quickly when filming 3 dives a day (150mb/s is already becoming a hassle to manage); and © HDR would likely require significant color grading time, which I don't really have for my day-to-day work. I try to get the colors as close to perfect in camera as I can since I have to produce a 30-45minute film every week :)

Share this post


Link to post
Share on other sites

There is no concept of native ISO a camera has a base ISO that depends on the gamma curve in use

For linear curves that include all normal modes for still pictures and cinelike mode the base ISO is 200.

For logarithmic curves that include VLOG and HLG the base ISO is 400 you cannot go lower.

If you set a minimum ISO of 400 on a normal gamma curve using profiles like natural or cinelike you are increasing noise and in turn decreasing colour depth and dynamic range

 

For what concerns the gain indicator dB and stops are on different scales the situation is quite weird and there is definitely something going on. When you set a log profile the two scales match 400 800 1600 ISO corresponds to 0 3 6 dB. When you set a linear profile the ISO goes 200 400 800 and the gain goes -6 -3 0 suggesting that 0dB is ISO 800 so I believe there is a bit of bug there when you use extended ISO -12 dB appears. I would completely ignore this gain display as clearly it has issues except in LOG.

 

In practical circumstances I found that cinelike D with leeming LUT is very useful shooting 10 bit 400 mbps. In situation of bright scenes you can force the camera to ISO 100 this is basically putting an attenuator on the circuit that will give you 1 stop for wider aperture or slower shutter speed so that you get the effect you like. I did some snorkelling in Marsa Alam and I used ISO 100 at the surface with 24p mode and 1/100 shutter speed and the camera stayed below f/13 which is what I wanted. I still occasionally got some clipped highlights (see example here https://youtu.be/T7E9g0z6F0U?t=201)

but overall I was quite happy, by the way skin diving with a video set up is deadly and you just can't get exposure right...

 

This is basically my understanding as well. I need to find a good article that covers the technical discussion, but in a nutshell, there's no direct relationship between the signal of the CMOS sensor and the ISO. For video, ISO is influenced by the gamma curve of the picture profile used -- ISO 400 in VLOG and ISO 400 in d-cinelike/standard don't produce the same exposure. Changing the ISO doesn't impact the signal from the CMOS sensor, just how the camera processes that signal into the video file. One (somewhat sloppy) way to think of it is that your ISO is a tradeoff between dynamic range, noise, and the distribution of usable dynamic range above and below middle gray. In VLOG, the GH5 can record about 11.5 stops of dynamic range at ISO 400. Go to ISO 800, and your overall dynamic range will decrease to 11 stops or so, BUT you'll get more of that range allocated to the highlights. So, somewhat counter-intuitively, higher ISOs actually protect the highlights a little better. Conversely, if you could shoot VLOG at ISO 200, you'd also lose a bit of dynamic range, but your shadows would be cleaner, so you'd get more of the remaining dynamic range allocated to the shadow regions.

 

When shooting in d-cinelike/standard however, the gamma curve of the picture profile itself will never allow you to record more than 9-10 stops of dynamic range. So whether you shoot at ISO 200, 400 or 800, your dynamic range is going to more or less be maxed in those profiles anyway. The only difference is that you'll get (slightly) less noise at the lower ISOs. Personally, I find almost no perceptable difference in the footage in terms of either dynamic range or noise in the ISO 100-800 range. So I just use whatever the exposure dictates.

 

 

Not to go off on a tangent...

 

The native ISO (the one where the SNR has been optimised) for the GH5 and GH5s (in Auto or Low mode) is ISO400 - which is where you will get 11-13stops, depending who you speak too.

 

If you set the camera to show SS/Gain instead of ISO, you will find that 0 Db is equivalent to ISO400. Changing the gain either + or - you will lose dynamic range, so ideally you want to fix that and either play with lighting or aperture.

 

As Dreifish mentions - ambient light is still bright! the last dive I did over Christmas period, I was shocked how much ambient light there was, as I was running the camera at C4K@30, 1/60, 0Db - and was having to go to f8/f11 to get correct exposure on my waveforms.

 

Yeah, the ambient light (especially in the tropics) is a big issue for trying to shoot blended-light exposures. Shooting at 60p (and 1/125 shutter speed) helps to keep your aperture around F5.6, which is optimal on a m4/3 sensor to minimize diffraction. I try to avoid F11 unless I really need the increased depth of field for macro (or with a rectilinear wide angle zoom in a dome port). That's why I'm always a little confused when people focus so much on a camera's low-light performance. Maybe they shoot in very different environments than I do. I almost never have to raise my ISO above 800 :).

 

Thanks Andrei! Hope you understand that i am asking to discuss and learn and not to critique :beer:

Panasonic states that the native ISO for the GH5 is 400. Dxo numbers are different anyway (eg ISO 100 on the camera corresponds to their ISO 64 if I remember correctly). Most users experiences also agree that ISO 400 they get the best results in terms of dynamic range, color and noise. I am not a pixel peeper so I cant tell. My thinking is that if you work at ISO 400 as a base you still got room to move down the range to ISO 200 if needed and still got very good results.

I understand the third light concept to cover something very close to your port and not wanting to move the lights in but does it have to be so bright since you will be so close?

I understand the reason for wanting to keep the specific exposure settings when it comes to maintaining the quality of the blue color. What IRE are you placing your blues at?

Agreed Vlog is not really needed underwater but its the only way (with the exception of HLG) to produce HDR content (which i think based on your footage you should :good:)

Thanks again for taking the time and for your always informative posts!

I rarely (never) find myself wishing I had less artificial light. Usually the opposite. But yes, technically, if you only use the middle light for situations when you're filming something very close to the lens, it could be weaker. Seeing as I'm usually starved for (artificial) light, I end up turning all my lights on all the time.

 

The question about the IRE of the water column is an interesting one. I haven't thought about it before.. I usually expose/grade by eye, going for a strong color contrast between warm subjects and blue water column. Looking at my past footage, it seems I like to expose the water column around 25IRE, sometimes a little lower. Almost never above 50IRE. Very curious to hear what other people do.

 

HDR footage is a whole other topic. In short, I'd like to produce it, but have too many limitations/compromises with my current gear. The biggest is that I don't have an HDR monitor for grading or an HDR display, so can't verify the results. Other minor issues: (a) no option for shooting in HDR and 60p on the GH5, and I favor 60p usually; (b) the 10bit 400mb/s All-I files add up quickly when filming 3 dives a day (150mb/s is already becoming a hassle to manage); and © HDR would likely require significant color grading time, which I don't really have for my day-to-day work. I try to get the colors as close to perfect in camera as I can since I have to produce a 30-45minute film every week :)

  • Like 1

Share this post


Link to post
Share on other sites

I could not agree more with dreifish for some reason it seems people make confusion between a function vs the objective

The ultimate objective of all we are saying is to reach the correct exposure. Dynamic range in itself means nothing is just a way to get the correct exposure.

From what I see there are broadly two categories of underwater video

1. Naturalist - people mostly interested in aquatic life most likely in shallow water or shooting macro with lights at any depth

2. Wreck - most typically in deeper water sometimes beyond recreational interested in wide angle with lights

 

Group 1 is concerned with too much ambient light at times and will usually prioritise frame rate for movement, determine shutter speed and aperture accordingly and finally take ISO to fit it in

Group 2 is concerned with not enough ambient light, lack of colours they will usually choose a single frame rate, determine shutter speed set the aperture to the value that does not give blur and then cap the ISO to a value where noise is manageable.

 

In practical terms both groups fit on the Manual mode with auto ISO on the GH5 with group 1 sometimes using extended ISO to limit light and group two setting a max ISO to limit noise

Your choice of lens determines if you need to set the aperture and can use S mode instead of Manual or not. In S mode the camera prioritise lower ISO so will close apertures as last resort useful mode with wet lenses where wide aperture are not an issue or with moderate wide angle (Leica 12-60) on a dome.

 

 

For what concerns the dynamic range of SDR this is between 6 and 10 stops (if you are lucky) so any ISO up to 1600 on the GH5 can manage it however having more helps to avoid burning highlights and crushing shadows in a scene. Again this is about exposing correctly setting an ISO to a fixed value only results in the other variable having to adjust

For example if you shoot cinelike or natural and you are at ISO 400 with shutter speed 1/50 aperture f/11 would you rather not be at ISO 200 and aperture f/8? As MFT lenses start dropping past f/8 probably you rather go for ISO 200.

 

If you are shooting log and you are at minimum 400 you will incur issues of diffraction because even with shutter at 1/100 or 1/125 at the surface the camera will jump f/11 and more

 

Generally log shooting appears inadequate to non studio underwater scenes but of course this is down to personal preference on the workflow tools available so for someone this may work

 

Drefish if I recall shoots 60fps at 150 mbps 8 bits and his footage looks great this tells you how important is correct exposure vs all the other theoritical concepts

Share this post


Link to post
Share on other sites

Sponsors

Advertisements



×
×
  • Create New...