strobe positioning W/A

[nortoda1 13]

I do most of my diving/photography in Ireland where viz can be 20m but most of the time it is 6m or less. For about 2 years I used a Sigma 15mm (great lens) on a D70 with 2x DS125s on 5" ikelite arms. I never had a problem with strobe positioning. I have been using the Tokina 10-17FE for a few weeks now and have also added 2x 8" bouyancy arms to the esisting 5" ike arms. and am having difficulty with strobe positioning. For wide angle shots I place the 2 x DS125s back about 8-12"s from the dome port and angle out to light with the edge to avoid backscatter.

My problem is that as I get closer to the subject (close focus W/A) the centre of the frame is not being lit. Is this because the port shade is blocking the light i.e. do I need to move the strobes more forward and closer to the port? How close? I assume I still point the strobes out to avoid backscatter.

Edited September 22, 2008 by nortoda1

[james 0]

This is a common problem. You'll need to either bring your strobes in closer, or else pull them back further. In murky water, I'd opt for pulling them back.

 

HTH

James

[stewsmith 14]

if you post an example of one of the images it will be easier for others to give you their thoughts. i have only just purchased this lens so cannot personally help, but i will be taking notes of the replies.

 

cheers, stew

[james 0]

When I was shooting really wide (17mm on FF) in the Philippines using 2 x DS125's I ended up using a third strobe in the middle.

 

Cheers

James

[Dupsbear 1]

Is this because the port shade is blocking the light i.e. do I need to move the strobes more forward and closer to the port? How close? I assume I still point the strobes out to avoid backscatter.

 

I shoot this close focus wide angle type image much of the time, even focusing as close as within 6 inches of my domed port by bringing my strobes in very close to the dome and angle the strobes to the outside. By close to the port, I mean within as close as 6 inches.

 

I am one of those that never uses strobe arms that extend farther than 14 inches from the port. By using the technique you described of directing the beam angle away from the port, I have very little backscatter.

 

Hoping this information helps,

Barry

[tdpriest 115]

as I get closer to the subject (close focus W/A) the centre of the frame is not being lit

 

Move those arms! Your principles are fine, but you have to keep the edge-light from both strobes overlapping on the subject.

 

Although it looks really awkward, I've also tried having one arm vertically above the dome, pulled back behind the housing, and one out to the side.

 

Tim

 

[bighead 0]

Does anyone have pictures showing the strobes position in CFWA ?? A picture says a thousand words ...

[ce4jesus 1]

http://www.kelpfish.net/strobe.html This is a great site. I go back there once in awhile just to refresh the basics.

[bmyates 3]

http://www.kelpfish.net/strobe.html This is a great site. I go back there once in awhile just to refresh the basics.

 

Ditto that! I have found his illustrations more helpful than almost anything else I've seen or read on this topic!

[tdpriest 115]

Does anyone have pictures showing the strobes position in CFWA ?? A picture says a thousand words ...

 

Martin Edge, "The Underwater Photographer" 3rd edition, has illustrations, commentary and advice.

 

Tim

 

[bighead 0]

Martin Edge, "The Underwater Photographer" 3rd edition, has illustrations, commentary and advice.

 

Tim

 

 

having said this, I think the live video demo of martin edge on underwatertvchannel is real cool ... where he teaches the basics of exposure on macro photography ...

 

thxs guys for the website on the strobe positioning for WA ... jus wondering if using a FE or a rectilinear lens affects the way the strobes are positioned ??

[glamourpuss 3]

my internet connection in the philippines is too slow to watch the undewater tv channel, does anyone know if you can download these videos instead of watching them streaming?

[tobbe 0]

Hi,

This is an interesting topic.

I need some advice regarding scatter and blurry edges when shooting CF-WA images.

Example of CFWA with a 19th century wooden wreck in background, using a Tokina 10-17 at 10mm:

 

I have experimented with different positions of the strobe arms, but i still get need to crop the images taken in dark water.

 

I was told to move the strobes closer to the housing and point them outwards (not 45 degrees as i used to), so i removed one section of the arms and had them linear with the dome, but i'm still not satisfied with the result.

 

Next dive i will try to pull back the strobes even further like this:

 

 

What do you guys think?

 

/T

Edited November 14, 2008 by tobbe

[tdpriest 115]

Try turning the strobes about 30 degrees outwards. You may need to move them a little closer to the back of the lens, but probably not. The centre of the frame is lit by the overlapping edges of each strobe's light, the centre of each light pool is off to the side, in your example shining on the diver's head and fins. You should have more even illumination and less backscatter.

 

Tim

 

[rjsimp 0]

It seems that if you put your strobes close to the camera and point them our away from the camera, you are lighting the particles on the side the wide angle lens will see. If you can imagine the WA lens having a 160+ degree viewing angle and you are pointing your strobes angled out away from the center, you are going to see more back scatter. You also run the risk of creating a shadow in the middle of your shot.

 

I have my strobes on 2 - 12" arms so each side can go out 24" from the camera. I then angle the strobes back a bit towards the camera and that gives me very good results without getting any backscatter. The only thing I have to watch out for is that they don't get too much in front of the lens or I will end up catching one of them in the edge of the shot. You need to keep them slightly behind the camera, but I would have them angled in towards the center a bit.

[tdpriest 115]

24" arms are a macho myth, once promulgated by the great and the good, including Martin Edge, then debunked by experiment. Backscatter occurs when the light rays from your strobe are reflected back at the lens: by moving the strobe to point outwards, and by positioning the strobe behind the port shade, no light rays are reflected back at the lens by the particles within the field of view: they are reflected away from the lens. This works with arms as short as 8", though 12" may be better, and a field of view up to 180-degrees. It is difficult with a circular fisheye lens...

 

Tim

 

[rjsimp 0]

24" arms are a macho myth, once promulgated by the great and the good, including Martin Edge, then debunked by experiment. Backscatter occurs when the light rays from your strobe are reflected back at the lens: by moving the strobe to point outwards, and by positioning the strobe behind the port shade, no light rays are reflected back at the lens by the particles within the field of view: they are reflected away from the lens. This works with arms as short as 8", though 12" may be better, and a field of view up to 180-degrees. It is difficult with a circular fisheye lens...

 

Tim

 

 

"Macho myth" Okay.. First, it is 2 - 12" arms on both sides giving you up to 24" of extension on each side.. Second, nothing mythical about it, it works, it was is the same set up that Cathy Church uses and has taught to me. I have looked at your pictures and I'll stick with putting the strobes further out and angling them in. To each their own, but I don't have ANY problems with backscatter and I am able to get much better dramatic lighting that gives more shadows and texture to the picture.

 

[Alex_Mustard 0]

Personally, I think that lighting is biggest area where most photographers struggle to produce high quality results.

 

The main mistake people make is not getting close enough. And then when they do they use too long arms or aim the strobes out - this was by far the most common problem with people's wide angle at the start of my workshop last week. Everyone lighting the edges of subjects and not the bloody subject!

 

I do most of my tropical wide angle with a single section of Ultralight, 8 inch section. I almost never aim my strobes outwards. There is no problem lighting a fisheye wide angle shot with a single strobe, if you know what you are doing.

 

Alex

[Steve Williams 0]

There is no problem lighting a fisheye wide angle shot with a single strobe, if you know what you are doing.

 

Ahhh, there in lies the rub. I'm far from an expert so I bow to your opinions, But it seems to me that there are far too many variables at work here to be able to define one way as "correct". Let's see, we have ambient light level, strobe power, strobe type, strobe angle of coverage, diffused or not, water clarity, strobe position, strobe angle, subject size, subject distance, particulate size, particulate amount, particulate reflectance and probably a few others I'm forgetting. The calculus involved in solving for these is far past my ability to provide an answer much less be adamant about it.

 

The real variable that drives discussion here especially on this subject is that we are all in different places on that big learning curve. What passes for a good picture for some, others would throw away. We are all on the journey and the beauty of Wetpixel is that the craft continues to grow and improve because we feel a responsibility to help those with less experience while at the same time learning from others with more. I'd say RJ and Tim are both right for what they are trying to do, really shouldn't be an argument. Take a look at the Strobist website sometime, 30,000 members discussing how to use and where to put their strobes. They are on dry land and they can't agree.

 

As I grow in my photography I'm paying much more attention to how I use the light. I'm starting to really understand that the light is the key variable that separates world class from just another good shot. With the advent of digital photography there are thousands of good pictures being put up each week on Flickr alone that would have been cover shots when I started diving. Now it's just another picture of an anemone fish. I'd offer that the pros like Alex and the others here who consistently produce breathtaking images that separate them from the rest of us use the light they need to make the image they want. I'll bet if you picked any six of their great images the strobes are in a different place for each one.

 

Where do you put your strobe(s) to take a good picture? I use a 5" and an 8" arm with the strobes pointed straight ahead so I can "scissor" the strobes in & out to the position that the light just makes it to the subject without lighting the water between us. Where do you put the strobes to take a great picture? Turn one strobe down (or off) so you get some shadows and highlights and put them where they need to be to tell the story. Where do you put them for a great image? Beats the hell outta me, but when I figure it out you guys will be the first to know.

Have fun,

Steve

[dhaas 32]

I second Alex's opinion on not needing for most shooting (if not all) more than two articulations in a medium short arm.

 

If you are shooting 4' or closer you can aim most wide beam strobes (I use one or a pair of Ikelite DS125 and now DS160) and the beam angle is more than enough to light the subject without backscatter. Aiming it almost straight ahead light a car's headlamp until maybe 1.5' or closer works fine. Maybe slightly above the lens axis and behind the "film plane" of your camera too. I position my strobe front edge equal to my housing's back. Sometimes even pulling it back further (maybe 6" behind the back?) as I move closer to a subject.

 

People always seem to make this WAAAAYYY more complicated than it is. Think of your flash as a paint brush (OK, a fairly a BROAD swath one) and aim it accordingly.

 

YMMV

 

dhaas

[scorpio_fish 5]

I was asked about strobe positioning on my last trip.

 

My first comment was, "There is one rule for strobe positioning. That is that is no one rule on how to position your strobes."

 

"Tobbe's" picture of his rig with the strobes pulled even further back is quite pointless. Regardless of the spread of light from the strobes, his rig is clearly going to block the path of light.

 

It's ridiculous to even provide some notion of where strobes should be. It depends on how and what you are photographing and where relative to the light source, your foreground subject lies. E.g., it's silly to think that your strobes should be positioned in the same place when shooting portrait versus landscape. My strobes are rarely symmetrically positioned. Nor are they often set on the same power setting.

 

There is no problem lighting a fisheye wide angle shot with a single strobe, if you know what you are doing.

 

Yes, but it's a kind of backward way of explaining it. If your need your strobe(s) to cover 100-180 degrees, you are either 1) not composing your shot very well or 2) diving in a cave.

 

The biggest error I usually see is that the shooter has no idea where his/her strobes are actually aimed relative to the subject.

 

24" arms are a macho myth, once promulgated by the great and the good, including Martin Edge, then debunked by experiment.

 

Sure, but it depends on how you create the protocol of the experiment.

[tdpriest 115]

...the same set up that Cathy Church uses and has taught to me...

 

That's a nicely lit shot, and three years ago I would have agreed with everything that you say, but after using shorter arms diving the wrecks of Bikini atoll in pretty poor visibility I thought about avoiding some of the difficulties of handling 24" arms around coral, and used 12" or 18" arms with no problems. I was ready to be convinced when reading Martin Edge's latest edition of "The Underwater Photographer" where he describes good results with short arms.

 

Single 8" segment with two ball joints, 10.5mm Nikkor:

 

 

Single 12" segment with two ball joints, 10.5mm Nikkor:

 

 

It's so much more comfortable with shorter arms...

... but long arms look so much more impressive.

 

I move my strobes around all the time, and often have one vertically above the lens, with the other out to the side. One is often powered right down, or even off. I'll try different positions and powers if the subject permits, and definitely bracket my strobes far more than exposure or composition. That was all much more difficult with 24" arms. I know that it's difficult to justify changing a technique that works for you, but it's pretty clear to me that there's more than one way to handle backscatter (not to mention using filters and side-stepping the problem completely by using ambient light) and that, as Alex says, it starts with getting close. Angling the strobe outwards is difficult, as you are trying to preserve illumination in the centre without having "hot-spots" at the edges, and I've often got it wrong, but it does allow you to get in close without long arms obstructing access and risking damage to both camera and subject:

 

Single 12" segment with two ball joints, 10.5mm Nikkor:

 

 

Tim

 

[rjsimp 0]

It's so much more comfortable with shorter arms...

... but long arms look so much more impressive.

 

Tim

 

 

Very nice shots Tim.

 

I am not sure why people keep saying 24" arms. I said I have two 12" segments to give me up to the max of 24" away from the camera. It gives me options is what it does. I can go right next to the camera to above, below, and to the side. I can go as close to the camera as touching the camera (not something I would do normally) to the 24" of extension and anywhere in between.

 

Flexibility to provide me options is what I am after. As far as ability to get into tight areas, well, I don't do wrecks really so I couldn't speak to that.. but I have never had a problem getting my camera/strobes where I want to. The arms also make a very good carry method when crossed over so it can be handed down and take back up for entry/exit.

 

Anyhow.. I just wanted to clarify, I am in NO WAY saying all my wide angles are always at 24" out from the camera. I position them where they are needed and with the arms I use, I have a LOT of options that I would otherwise not have with a different set up.. After all, shooting underwater is all about options in order to get the best shot.

[vazuw 1]

For me strobe position depends on what you want in the photo. I always wonder what people are doing when their strobes never change positions. The answer is you keep getting the same shot. I use a double arm on each side because it gives me more flexability, to up light, backlight or whatever. As a wide angle guy I try to visualize what type of light I want the subject, or situation, to have. For example I may downlight to try and enhance a sunlight effect on the subject , or spotlight something to make it stand out, backlight to add textue. The point is move them around

Edited November 27, 2008 by vazuw

[vetdiver 8]

Just saw this thread, though it seems like it's been abandoned, I'll post anyways. I am taking in every word here - I also shoot almost exclusively in dark/murky water and I have also had difficulties with CFWA shot lighting and backscatter. I use 2x 5 & 8-inch arms (I have 12 inch arms, but they are huge and annoying...). I have been shooting with either both strobes close to and slightly behind the port (I'll tend to get backscatter when there isn't an object right in front of a strobe) OR one strobe as far away from the post as possible (facing open water) and one close and slightly behind the port to light an object. In all cases, both are pointed about 30% out.

 

The other issue I get on occasion is a "hot spot" , though I've heard that this can be lessened by angling the strobes slightly up (any comments on that?). Sill, balancing the foreground and background in dark water can drive me to the brink of insanity.

 

I recall, Alex, when you were out here, that you told me you almost always keep your strobes close to your port when shooting WA - did I remember that correctly? Tim - I never thought of putting a strobe above and pointed out - I am really excited to give that a try - I have been "cheating" by putting my close subject of to the side a bit, since this is the only way I've been able to accomplish anything reasonable.

 

I have seen beautiful dark water shots from all kinds of crap conditions, and I really feel stongly that this is an area in which it is possible to do well with perseverence and hard work - someday, I'd like to be able to have a WA lens on for particular sites without worrying about conditions, knowing I might still be able to get salvageable shots even with 20 ft or less of visibility.

 

Allison

Edited December 17, 2008 by vetdiver