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davec13o2

Manual and TTL

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I'm trying to decide if it's worth the expense and risk to purchase a TTL converter ($400) and two new strobes ($1600) or stay with a manually controlled strobe. I've found it a challenge on drift dives in a group to get consistently good shots on manual strobe control with limited time at a target. I would like to have a reliable TTL as a backup.

 

I've been using two camera systems: Meikon a7RII case with ST-100 strobe (wired connection) and RX100iv in Fantasea case with YS-03 strobe (fiberoptic connection). I've taken these setups to the Red Sea, Cozumel, and Palau/Yap and have gotten mixed results for wide angle and macro. To find out more, I've tested both on a bench with oscilloscope and photodiode to determine pulselength for various conditions.

 

The Meikon/ST100, wired, works only in manual mode and the ev controller does control output. For ev=-2 pulselength=365 microseconds, ev=0 pulselength=900 microseconds, and ev=+2 pulselength=2.8 milliseconds. Wired TTL with the Meikon 2-wire connection from the camera hot shoe does not work.

 

The YS-03, fiberoptic TTL, works with some reservations. Results are shown in the table.

 

The scene photo taken with the camera alone set for large aperture and high iso (test 1) gives a photo exposure that matches what is seen by eye. For the camera operated with its flash and set to low sensitivity (test 2) the photo is underexposed apparently because the on-camera flash does not have sufficient output. At high sensitivity (test 3), the on-board flash does a good job of lighting the scene. With the YS-03 and the camera set for low sensitivity (test 4) the exposing pulse is relatively long (600 microseconds) and the scene is well lit. TTL works well. At high sensitivity (test 5), although the camera should detect that the scene will be over exposed, the strobe still fires with its minimum pulselength and does indeed overexpose the scene. Apparently, the camera can't interrupt the second exposing pulse even thought it's not needed. Of course, in real life, I would use much higher f/number and lower iso, so amount of overexposure would be reduced.

 

My questions are:

1. Does TTL generally work with enough sensitivity to handle a wide range of conditions, or is it just a marginal nicety?

2. Can TTL get you close to the correct exposure where an ev controller could be used to dial it in?

3. Would a third party TTL converter and high end strobes do better in terms of nuanced control than my RX100iv and YS-03?

4. I'm thinking of getting a couple of Z330 from a US vendor. I figure repairs would be easier than purchasing a strobe from a foreign supplier. Is that right?

 

Any comments and suggests would be much appreciated.

 

 

post-77081-0-19537000-1544647467_thumb.jpg

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Ah ha, so ST-100 driven off internal flash is restricted to about 1/3 of its potential power. Good to know, even though I have pre-ordered a pair of Retra Pros two days ago, since ST-100 power proved to be more than a little disappointing on my last trip.

 

Regarding TTL, I used Sony A6300 with a pair of ST-100s over fiber optics, camera in manual mode, f/8, 1/160, auto-ISO 100-12800, AF-C, and it was just point and click. TTL did not produced any overexposed images, but the ISO generally hovered in the 400-1000 range, suggesting a general lack of power in the strobes, and on larger subjects, they failed to overwhelm the natural light, resulting in semi-ambient light shots and requiring significant color correction. Note that this was all wide-angle with 10-18mm lens and 7.5mm fisheye - I have another trip coming up in seven weeks where I'll test this setup with macro.

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Right, I've given up on the ST-100. To solve the problem, I've also convinced myself that I need two of the Z330 or the Retra. My thought is that, although I would prefer a Retra, it may be better for me in the US to get the Z330 in case I need service, in which case it would be easier sending the unit to a US facility.

 

For my kind of shooting, mostly group drift diving, I need to be ready for both semi-macro and wide angle. It seems like the best solution would be a wide angle zoom with a magnetically attached diopter lens. That combo worked fine in Palau, except of course, for the strobe issue.

 

I don't usually have time to fiddle with manual strobe settings, so I need a reliable TTL setup. I'm hoping I can get that with the Z330 or Retra and the soon-go-be-released UW-Technics TTL converter. I'm willing to spend $2000 for that setup. I just hope the resulting TTL is effective at low required intensity for macro, even with very small aperture and moderate iso.

 

Is this logic correct: In order to reduce the ambient contribution (which is at the wrong white balance and color temperature) you operate at small aperture and let the iso float while setting shutter speed to accommodate the strobe pulsewidth.

 

What's your next destination? Have you done Raja Ampat, Anilao, or Komodo yet?

Edited by davec13o2

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1/160s is the maximum sync speed for my camera; you could do 1/250s with your A7R II, or up to 1/2000s with RX100M4, although shutter speeds that fast start cutting into strobe power and are usually used only for shooting sunballs and the like. The small aperture reduces ambient light contribution, increases depth of field, and improves sharpness (AFAIK, Sony 10-18mm is at its sharpest at f/8-f/11). At least with the limited strobe power of ST-100 and wide-angle scenes, Sony's metering algorithm appears to be reasonably accurate at balancing strobe power and ISO. I'm going to Koh Lanta in Thailand for 8 days in February and I'll try to shoot a mix of wide-angle and macro with ST-100s, 10-18mm and 90mm, then I hope to do a longer trip to Philippines in October, for which I will - hopefully - have the Retras in my bag. Indonesia is difficult and expensive to access with my passport - have to go with an organized group sponsored by a travel agency.

Edited by Barmaglot

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Your style of shooting sounds similar to what I do. Running two INON Z-240, camera on f8 I just try to get about the same difference from everything sometimes a little low on flash sometimes a little high and adjust it in RAW later if needed..

 

I really don't follow what you are doing with your tests. The YS-03 is TTL only and ST-100 I don't know how it performs, but your test indicates it is underpowered.

 

As to what to do, you can't go wrong with better quality flashes. If you get INONs or Retra or similar you can run them in either TTL or manual. TTL will work directly with the onboard flash of the RX100 or you dial the onboard flash compensation down and use them in manual. The A7R-II of course does not have a built in flash and you need a trigger to do TTL, but believe you can do wired manual. TTL is more hit and miss in general on wide angle and the success or otherwise depends upon the cameras internal TTL system as much as anything else.

 

On your macro question, just increase the aperture, the flashes should be able to do ISO100 af f16-22 (on the full frame A7) You don't want to get down to such small apertures on the RX100. But it's really not a problem unless you want a black background, I'll shoot at f8 ISO400 on my m43 system and the BG colour goes to blue/green depending on what water you are in and I don't mind that effect. If you want to darken the BG, fix the ISO at minimum on the RX100, you could float it up a bit on the A7 as you are stopped down more and flash will recycle faster.

Edited by ChrisRoss

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I really don't follow what you are doing with your tests. The YS-03 is TTL only and ST-100 I don't know how it performs, but your test indicates it is underpowered.

 

 

Regarding ST-100, the problem is not that it is underpowered, but rather that it has a really stupid optical trigger circuit - it basically works the same as YS-03, blindly following the triggering signal without modifications. When the camera flash only burns for 0.9ms, and the strobe needs 2.8ms to fully dump its capacitors, this effectively restricts its output to 1/3 of maximum. Manual operation is the usual counter to this issue, but on ST-100, manual operation works only with wired triggering, and optical TTL compensation is not implemented - it's basically a bulkier YS-03 with a focus light. An LED trigger might help, provided the strobe is sufficiently sensitive, but I don't know of anyone who has tested that combination.

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As to the question of what I'm trying to do with my tests:

 

When I got into this game a bit over a year ago, and not knowing whether or not I would stay with it, I looked for a cheap solution to the seemingly expensive strobe problem. I didn't want to spend twice as much for the housing and strobes as I did for the camera.

 

I read the description of the Meikon strobe which said "TTL", and naively figuring that would easily mate with their case, I bought both. Then I found out that with the wired connection from the Meikon case to their strobe, it would not fire under TTL, but would under Manual. With a garage full of test equipment from my small laser business, I began testing; and I sent the results to Meikon, which they verified. That was a surprise.

 

So now I have two strobes that don't do the job. I'm trying to figure out with the two what questions about TTL I should ask before spending another $2000. Ideally, someone will be able to tell me what pulselengths (second pulse under TTL) they achieve with a UW-Technics converter and a GN30 strobe. Then I will make the leap of faith that the to-be-announced UW-Technics converter for Sony a7 and a Z330 or Retro will behave in the same way. I'm also making the assumption that if this doesn't work out, I'll be able to return or sell a set of popular, lightly used strobes, and perhaps the converter as well.

Edited by davec13o2

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Basically the best value for money would still be ST-100, if you could drive it with an LED trigger to enable its full output, and if the metering in this TTL-only mode is sufficiently accurate. The 2.8ms full duration isn't far off from Z-330's 3.3ms, and the bulbs themselves are probably not that much weaker. I'm still kind of on the fence about the Retras - while they're undoubtedly excellent strobes, €1478 plus import taxes is still a lot of money - if someone verifies that either the Turtle or the UW-Technics trigger works properly with ST-100s (i.e. reaches full power when needed and provides reasonably accurate exposure), I might cancel the pre-order and stick with the SeaFrogs solution. Even as it is, my setup produces some shots that I'm quite happy with (example), but it is kind of frustrating that 2/3 of the strobes' power is locked away and inaccessible.

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Your examples reaffirm my belief in strobe lighting after the duds I got recently. I'll continue the struggle for TTL.

 

As soon as the UW-Technics becomes available, I'll do the tests you mention and report here. If the ST-100 fails, then I'll be looking at the

Z330 or Retra. I suppose I should lock in the Retra pricing within the next 10 days and cancel later if needs be.

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At the risk of being somewhat argumentative, I have yet to find a TTL solution that really works consistently when shooting wide angle.

 

Whilst the mechanics of metering and flash exposure are technically possible, the TTL circuits have no way of actually determining which part of the image they are actually lighting. To balance using strobe light to light the foreground and ambient light for the rest of the image is a challenge.

 

With practice, using manual control of strobes is actually pretty quick and efficient.

 

Adam

 

 

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Your point is well taken and appreciated. I've heard the same from many sources; and lacking sufficient experience, I can't add to it. I'm hoping TTL will get me in the ball park from which I can make ev adjustments. I'm hoping that eventually I'll have the experience to go manual.

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Your examples reaffirm my belief in strobe lighting after the duds I got recently. I'll continue the struggle for TTL.

 

As soon as the UW-Technics becomes available, I'll do the tests you mention and report here. If the ST-100 fails, then I'll be looking at the

Z330 or Retra. I suppose I should lock in the Retra pricing within the next 10 days and cancel later if needs be.

 

Believe me, I got plenty of duds as well - those photos are cherry-picked from a dozen dives, and I'm sure that in the eye of an experience photographer, they represent nothing more than a newbie stumbling around.

 

At the risk of being somewhat argumentative, I have yet to find a TTL solution that really works consistently when shooting wide angle.

 

Whilst the mechanics of metering and flash exposure are technically possible, the TTL circuits have no way of actually determining which part of the image they are actually lighting. To balance using strobe light to light the foreground and ambient light for the rest of the image is a challenge.

 

Even with spot metering? I mean, as I understand it, the challenge with TTL underwater is that the camera doesn't know that it's trying to light up water and ends up over-exposing the foreground in a vain hope to light up the entire scene, but I used spot metering on that trip, which only evaluates the center, and with some exceptions (mostly where strobe power was totally insufficient), the exposure looked pretty good to me, even if the camera had to raise the ISO setting way up. I can see how it will fail if the center of the image is water (there's no way to move the metering point), but other than that, it seems pretty good...

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At the risk of being somewhat argumentative, I have yet to find a TTL solution that really works consistently when shooting wide angle.

 

Whilst the mechanics of metering and flash exposure are technically possible, the TTL circuits have no way of actually determining which part of the image they are actually lighting. To balance using strobe light to light the foreground and ambient light for the rest of the image is a challenge.

 

With practice, using manual control of strobes is actually pretty quick and efficient.

 

Adam

 

 

 

I have to agree with Adam, when you shoot wide angle the strobes are not pointing straight to the subject the light bounces back at an angle and the TTL circuit usually gets it wrong

I found TTL to work well only in portraits and sometimes in macro the issue to consider is that the whole frame comes exposed and this actually can be an issue when you have distracting backgrounds

For wide angle I would not bother you know the power you have to use at a given distance I tend to keep the strobes wide open set the power on and make sure I am at the right distance.

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@Barmagalot-spot metering uses a metering zone in the center of the frame, so unless you use AE-Lock (and even then, I am uncertain if this locks TTL exposure) you are creatively limited as to where you put the subject.

 

The other problem with using TTL is that if you get good results, it is hard to diagnose how or why they have occurred. It is hard to replicate the recipe...There are simply too many potential settings to know why the image is well exposed. Hence it tends to limit the actual process of learning how exposure works.

Manual exposure and manual strobe settings are actually simpler to use. Once you have a setting that you like, you can repeat it as often as you wish! You can't learn manual exposure control while shooting TTL!

 

Adam

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The biggest problem with TTL I think is it tends to be random, a small change when you frame the shot again like the fish has moved relative to the background and the camera decides to do something different.

 

Also recognize TTL is camera specific, the camera is making ALL the decisions about how long to fire the strobe for. The strobes just do what the camera tells them to. There is some variability in how well the strobe mimics the trigger for TTL circuitry but ultimately it has to do with how the camera interprets the pre flash. The strobe provided it puts out enough power doesn't really come into it. I too had a go at TTL for wide shots and rapidly gave up, sometimes it would over power, others times it would barely put out any light. Macro is a different story the frame is filled with subject many times and the camera has an easier time of it.

 

The trick with manual is to get the same distance away when you shoot, I've been able to make it work for with the camera at f8 and the same settings on the flash for most shots. I'm slowly getting used to adjusting things but in the meantime I'm getting images I'm happy with.

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spot metering uses a metering zone in the center of the frame, so unless you use AE-Lock (and even then, I am uncertain if this locks TTL exposure) you are creatively limited as to where you put the subject.

 

Adam

Adam, I think it's more complicated than that. While it doubtless varies from camera to camera, my understanding for the Nikon D500, is that the spot metering zone relates to the focus mode. Spot metering locks a small metering area to the centre of the frame only when Auto or 3D focussing modes are engaged. For Manual focus, Single Point and AF-S Dynamic Area, it is the user selected focus point that determines where the metering zone is centred. For Dynamic Area AF-C and Group AF-C, the user selected focus point initially determines where the metering zone is centred but the camera may move both the autofocus point and spot metering zone if it detects that the subject has moved within the frame.

 

So for spot metering without AE lock, you are only limited to where you place the subject in frame in Auto or 3D tracking focus modes.

 

Returning to TTL, my understanding is that engaging spot metering on the D500 alters the TTL algorithms used by the camera so that it no longer tries to balance the strobe output with ambient lighting of the whole scene but instead, adjusts the strobe output to correctly expose what it thinks is the main subject - i.e. the subject material around the metering spot. Where the metering spot is relates to focus as above. Again, the detail of this complexity probably varies from camera to camera.

 

Mark

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Interesting - Sony doesn't appear to be this sophisticated. Looking at the user manual, I see this:

  • Multi - Measures light on each area after diving the total area into multiple areas and determines the proper exposure of the entire screen (Multi-pattern metering).
  • Center - Measures the average brightness of the entire screen, while emphasizing the central area of the screen (Center-weighted metering)
  • Spot - Measures only the central area (Spot metering). This function is useful when the subject is backlit or when there is strong contrast between the subject and the background.

I don't see how AE-lock would help - it'd need to fire the pre-flash, then give you time to recompose before firing the main flash, and to my knowledge no camera does that. Still - I don't know whether it's my rudimentary composition skills, or the weak strobes, but so far I've found TTL to be pretty accurate.

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Sony doesn't appear to be this sophisticated.

As I said, functionality varies from camera to camera. Sony introduced an option to link spot metering to flexible spot focus mode on the A6500 (which my wife has) but not the A6300.

 

I don't see how AE-lock would help

 

 

No, but the Sonys do have a flash-lock function (FV lock) that can be assigned to a button. Can't say I've used it but as I understand it, it allows a TTL flash exposure value to be calculated from a pre-flash and stored and then recalled following recomposition as often as you like. Might be useful in some circumstances, but perhaps that would negate much of the theoretical advantage of TTL?

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Learn something new every day... it's called FEL lock rather than FV lock, but it looks like it can be used to do precisely that - meter on a subject with a pre-flash, then recompose and use the metered value for the next shot, which skips the pre-flash. Thanks!

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Canon Have had an FEL function for many years starting with the T-90 film camera, you pressed a small button next to the shutter button and the camera pre flashed and stored the value, it worked quite well.

 

Back to the OP question. I assume you have seen this thread: http://wetpixel.com/forums/index.php?showtopic=62305 where it is established the buttons don't do as labelled, seems like it's just a TTL flash and as discussed here seems to be limited by the pulse time of the trigger. Basically it's an incompletely reverse engineered knock-off. The question is raised regarding the INON or Retra options and whether they suffer the same issues and the answer is no, they work, I've used TTL for macro shots and as long as the subject fills the frame they seem to work just fine, but if you try something like a nudi perched on a sponge with black water BG, it goes back to hit and miss, The only risk is whether the the TTL triggers will work, the flashes will be fine. The Retra is still not available for purchase as it's being re-developed, so that leaves INON. They have a good reputation and if the camera can work out the right exposure it will provide the required light.

 

As it stands your connection options are the non-TTL Nauticam triggers and Turtle offers a TTL option that either mounts in the hotshoe or separate cable to the hot-shoe. With a different housing there would be more options for example a wired TTL connection with an ikelite housing and ikelite strobes. The real question is how well the TTL trigger will work. The non TTL options are available now and I would expect they are reliable. The INON strobes have a very sensitive trigger so should not have any problems with the non-TTL triggers offered as long as the LEDS line up with the fibre optic ports on your housing.

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