for beginners - strobe positioning

[Chris Bangs]

This question came from "The cat keeper" on another topic.

since you asked... let's talk about strobe positioning first

I have been told that if I want to take a panaromic shot in the water, I should place my strobe at the furthest possible distance away from the camera to minimize backscatter... so I tried pushing my strobe to the furthest horizontal distance from the camera and there is still backscatter, so I moved the strobe to different angles (still maintaining the furthest horizontal distance from the camera) and still, backscatter everywhere!

Hence the questions are:
1. If there are particles in the water, is it possible to avoid backscatter at all? Or is the effort only, at best, minimizing those blotches on the photograph?

2. When I tried positioning the strobe at different angles, I realized that the light cannot reach the subject at certain angle... so what exactly does it mean by placing the strobe as far from the camera as possible while preventing the particles from reflecting light back to the camera?

Answers ) that depends on how much suspended particles there are in the water. Increasing the strobe distance from the lens will reduce the size of the reflections off the particles as the angle will bounce the strongest reflection away from the lens, but it will not eliminate the particles ( only photoshop can do that ). What you want to do is try to position the strode so that the beam will contact the subject while not illuminating the water between the camera and the subject. this takes practice. One tip is unless you are shooting macro and a subject is very close to the camera, keep the strobe pointed parallel with the lens, do not try to aim the strobe at the subject as doing so will result in more of the beam striking the water in front of the subject. I use real wide beam ( 110 degree ) strobes, and in dirty water I even point them slightly outward. I also use two strobes in most cases and my goal is to have each beam strike the subject with just enough overlap to expose the entire frame.


And,
3. We found a ray under some corals. There was an opening. My friend moved her tiny (compared to mine anyway) little camera into the opening and took the picture. With the bracket and the strobe, my camera has became really bulky... so now I could not access smaller crevices to get nearer to the ray without banging the strobe onto coral or something (and I do not want to do that)... so what's the best way to get to the ray?

Answer, The best answer to this is having a very flexible strobe arm, or better yet, one that can easily be detached from the tray/camera to allow more positioning options. Slave strobes designed with a sensor that needs to be pointed directly at the internal camera flash may make this more challenging as it reduces the positioning options. In such a case of your ray, I would most likely have tried to position the strobe by hand holding it, behind the camera, therefore not having to stuff it into the tight opening.

[Mike Veitch]

Hey Chris,

Good answers, i'd like to add my 2 cents as well.
A couple of tips i like to tell my students when dealing with very murky/backscattery conditions.
1 Shoot up, the scatter doesn't show up so much against a blue background
OR
2. If the conditions permit, ie you are wall diving, shoot toward a finite position. If you are trying to take a picture of a fish, take it from a position where the fish is against the reef instead of against open water. When the strobe light travels past the fish and hits the wall there is no backscatter to light up, just the reef and therefore no scatter.
If there is nothing behind the fish but open water then the light continues to travel and light up each and every piece of particulate.

Conclusion:
In murky conditions try to shoot in situations where you get the least amount of water between your subject, its surroundings and your lens.

[lukeROB]

Awesome tips guys.
Definately agree that you want to have your strobes pointed parrellal to the lens.

My little tip is to have the strobe positioned directly in line with the lens or below it for wide angle. I know this is not considered proper practice as it look stange to have light from below instead of above as this is the way we view the world. However I try to light my subject with the strobe and the rest with natural light. I find a high strobe position illuminates more particles or possibly the backscatter is now located in a less offensive position.

[Chris Bangs]

Mike and LukeROB thanks for adding very good info.

one more note, If you have a big subject and only a single strobe then center the strobe directory above or below the lens as this will provide more even coverage, and of course try to get the strobe as far away from the camera/ lens as possible.

[the_cat_keeper]

Answer, The best answer to this is having a very flexible strobe arm, or better yet, one that can easily be detached from the tray/camera to allow more positioning options.
Wouldn't the fish disappear by the time I detached the tray from the camera? :( I guess I would try this only if I were taking picture of a more "stationary" creatures like the eel or a nudibranch...

[the_cat_keeper]

Thanks everyone... and one more question: What if I were taking picture of a really big fish, say the whale shark or a big huge school of barracudas?

It would be difficult to get too close to it and to take the picture of the entire school/fish, I would have to be at a distance, and it would be really difficult to prevent backscatter. At the same time, the strobe is effective up to a certain distance so chances are the strobe won't do any good. So does it mean that if I were taking such pictures, I should just forget all about the strobe and hope that the picture turned out okay?

[Chris Bangs]

Hi many fish are territorial and tend to stay in a small area, you have to just sit and watch and fire when ready.

as for whale sharks, natural light is the way to go. Barracuda can be shot both with natural or artificial light. be careful though barracuda are VERY reflective! that will be address later as it tends to be more advanced.

Time to leave, do not want to miss my flight to Guam. nice to see that there are no typhoons in the area, feel sorry for the folks in Florida! On Guam however our homes are solid concrete, good thing as PAKA in 1997 pounded Guam with 236 mph winds ( 360 KPH, ish ). No power for 2 months!

[the_cat_keeper]

Time to leave, do not want to miss my flight to Guam. nice to see that there are no typhoons in the area, feel sorry for the folks in Florida! On Guam however our homes are solid concrete, good thing as PAKA in 1997 pounded Guam with 236 mph winds ( 360 KPH, ish ). No power for 2 months!
Thanks... and have a good trip.

[Alan Wiggs]

Just to add one more comment - I was taught to ideally always work to a maximum of 1/10th of the visibility. That means if you have 10 metres vis - your subject better be less than a metre from your lens. I find this means less break up of focus as there is less water column (less particles and backscatter) between your lens and the critter. If you push this rule your shots will be washed out and the flash will be ineffective. Simple rule is to get in as clase as you can - I see too many beginners stand off the subject; zoom to telephoto and wonder why their butterflyfish portrait is washed out; blurry and blue. Enjoy!

Wiggsy.

[Chris Bangs]

Hi

back on the rock!

Not a bad rule of thumb for flash photography but remember no matter how good the vis is subjects more than 2 meters away will be out or range for most internal flashes. Even with my dual flame throwers, 2.5 meters is pushing it.

For natural light shooting what you see is what you will get! in low light conditions,

I have seen the washout effect caused by the camera software attempting to adjust the light levels in the "post" processing of the image. so what looked like a over exposed image was actually an underexposed image that got some major brightening up. such images can be easily corrected in photoshop

[the_cat_keeper]

Seems like if I could get as close as possible to the subject, the picture can't turn out too badly? There would colours, minimal backscatter and the subject fills the frame.


such images can be easily corrected in photoshop
Going off the discussion a little, I've read a number of posts on using photoshop to enhance the pictures... everyone seems to be doing that... Is photoshop the answer to a good picture? Is there anyone who don't use photoshop at all?

[Chris Bangs]

Photoshop can improve a good shot by removing backscatter, correcting color, and even a bit of sharpening. It is not a magic wand, therefore if the shot is poor, out of focus, severely under or over exposed, photoshop will not resurrect it from the cutting room floor.

[Peter McGuinness]

One tip is unless you are shooting macro and a subject is very close to the camera, keep the strobe pointed parallel with the lens, do not try to aim the strobe at the subject as doing so will result in more of the beam striking the water in front of the subject. I use real wide beam ( 110 degree ) strobes, and in dirty water I even point them slightly outward. I also use two strobes in most cases and my goal is to have each beam strike the subject with just enough overlap to expose the entire frame.




Chris, I am finding this discussion very interesting, so thanks for leading it. Your answer above begs another question: why such wide angle strobes if you are pointing them away from the subject? I imagine that narrower beams would be more efficient in the sense that less powerful strobes could do the same job. This becomes interesting if it means I can buy smaller and lighter (possibly cheaper) strobes.
This is quite important to me because I do a lot of surf entries, so compact, mangeable equipment is a must.

I am sure that there is a direct relationship between beam angle, distance of throw, and power of strobe. Since I am about to get a strobe for my Canon, would I be restricting myself needlessly if I went for the most compact strobe, and what would be the downside of going for a narrow beam angle?

Thanks,
Peter

[Mike Veitch]

Hi Peter, don't mean to hijack Chris's thread but i can throw some light on this for you (pun intended).

The problem with narrow beam strobes is that they are narrow. This is fine if you want to do macro work only. However, in wide angle you need to cover a lot more area and therefore need wider angled strobes. When using a narrow strobe it won't be able to cover such things as sea fans and other larger objects. You will light up the middle but not the edges, therefore taking away the impact from your photos. Both wide and narrow strobes will get the middle but only the wides will get the edges. More importantly for your question, if you are in murky conditions when you need to turn the strobes slightly out, the wides will be wide enough to get the middle of the subject whereas you may not get the overlap with narrows and therefore have a dark spot in the middle of the photo, not good.
If you went for compact strobes with narrow beams and low power, i would think that you will find the limitation of these quickly and would then want to move to a better strobe in the near future. Do yourself a favour and get a good powerful strobe now so you don't need to needlessly spend more money in the future.
As for the actual size of the strobes vs width of beam for your purposes, have a look at Inon Strobes. These are a very compact strobe that has a wide beam.
If i didn't already own a bunch of strobes, i would probably go with Inons due to their compactness and power.

[Chris Bangs]

thanks Mike

you said it all for me!

just got back online after a major computer crash. hope to get back up to speed soon.


chris

[Peter McGuinness]

Hi Peter, don't mean to hijack Chris's thread but i can throw some light on this for you (pun intended).




Thanks, Guys.
I'm off to buy a strobe!
Peter

[Mike Veitch]

just got back online after a major computer crash. hope to get back up to speed soon.


chris

Whoa! Hope you didn't lose any photos.

[Chris Bangs]

Thanks Mike

no worries!

I make Triple back ups ( and even more on the prime stuff ) seperate drives, CDR/DVD

mitsui or Kodak Gold media for archiving.

[Chris Bangs]

also keep full sets in Japan as well as Guam. the old off site storage thing, so even if my office goes up in flames, still have my images.

the big film disadvantage! if not scanned, can only have one true copy.

[Peter McGuinness]

Well, I got myself a tray and strobe for my canon. Several hundred dollars poorer, I took it down to La Jolla to play with the new toy. Got myself several really crappy, crappy, crappy pictures!

Actually, to be fair to myself, I did get two pictures I thought were OK, and most of the reason I was disappointed is that I found nothing really very interesting to photgraph, but there is a lot to work on.

When you were starting out, how did you get a handle on the variables? Did you just set most of the parameters to some fixed value and work with one variable at a time?

Peter

[Chris Bangs]

When you were starting out, how did you get a handle on the variables? Did you just set most of the parameters to some fixed value and work with one variable at a time?

Peter[/QUOTE]

Hi Peter

adding a strobe will allow you to get some real good stuff, BUT it requires a lot more practice to get right.

here are some suggestions

first you need to understand how your strobe works and also how its power settings work with different apertures and distance. there should be a chart in the manual. feel free to PM me with your setup info and I may be able to get you in the ballpark if I have access the the manuals

Many times, new photographers try to go and shoot everything from Macro to wide on a single dive. this will make it very difficult to learn!

First concentrate on a single type on shooting based on subject distance. I suggest macro to start! then set your camera aperture to match one of the power settings on the strobe based on the subject distance. then start shooting. If your camera is digital do not worry about what you shoot at first. take a shot, check the results and make a aperture or strobe power adjustment to correct the exposure. with macro adjusting the strobe distance will also have a effect on the flash exposure. to bright back it off, not enough get it closer. try to avoid pointing at the subject, aim it past above. do this untill you see the best results

once you have it dialed in then look for some subjects. that fit within your type of shooting

[Chris Bangs]

forgot something important regarding the strobe setting chart

you also need to know the ASA value ( film speed ) inorder to use the settings. digi cams allow this to be adjusted in most cases.

for macro, I suggest 100 asa.

chris

am working on some more begginner threads addressing basic exposure control. (aperture, shutter speed ) hope to get them posted soon

[Peter McGuinness]

Thanks Chris.
One thought - is there any value in rehearsing this whole thing on dry land? I get a lot more opportunity to do that, of course.
Or does the different light absorption characteristic of water make it a useless enterprise?

Peter

[Chris Bangs]

For macro working in air may get you in the ballpark but you will most lilely need to reduce flash output a bit or open the aperture up, once in the water.

otherwise not worth trying on land

[regtech17]

Hello, i was wondering if you are shooting your strobe in ttl mode, this is great topside but underwater ttl gets fooled by the bluewater. I find manual strobing works the best. Especially when you understand f stops iso speeds.

regtech

[Chris Bangs]

Hi,

I shoot everything manual as that gives me much more control over the exposure. Topside I use it often and make adjustments via the "flash compensation" control on the camera.

[Scubakevdm]

Hey, I'm back! My strobes are here. I have two SB-105's, but only a single sync cord. Should I just use manual settings and slave one? And if I do, do I need to bump down the power on the strobes, or just use the ones on the chart be careful not to overlap them?

[Chris Bangs]

Hey, I'm back! My strobes are here. I have two SB-105's, but only a single sync cord. Should I just use manual settings and slave one? And if I do, do I need to bump down the power on the strobes, or just use the ones on the chart be careful not to overlap them?

Manual works best, I find that using the strobes with diffusers produces better results. I usually use 1/4 power for most situations unless shooting very wide angle

[Scubakevdm]

Manual works best, I find that using the strobes with diffusers produces better results. I usually use 1/4 power for most situations unless shooting very wide angle

Hey thanks man! Hopefully tomorrow the wind will subside and I'll get to try it out. I must say though, that I was very surprised by the amount of light that made it to the film in my sans strobe efforts.

[Scubakevdm]

Woo. I think I may have to tone the strobes down to 1/16th. I overexposed several shots of a hawksbill turtle so badly that the gallery crashed when I posted them.

[Wolverine]

Sorry to resurrect a very old thread but since it is already in place.. i was wondering on how you would place dual strobes for macro shots? For wide angle it seems apparent but I am curious on how you guys approach macro.

Reason for asking: Just got my second strobe (D2000w) and I am going to Maldives in 2 weeks.

[bobf]

Tim,

So many options! Each composition or goal would necessitate it's own special requirements. But in general:

For close macro work one technique would be to position the main strobe just above the lens, aiming downward at an angle. The fill strobe would be set to the side, aiming in towards the composition. In macro work backscatter is not as much an issue so illuminating the water column between the lens and the target is an acceptable practice.

It was explained to me is that the position of the main strobe in the previous example recreates where one might assume the Sun to be naturally positioned in the sky. The responsibility of the fill strobe would be to minimize (not eliminate!) the shadows created by the main strobe. Shadows do create depth and therefore a three dimensional feeling to the composition. It is best not to eliminate shadows completely.

In this example the power level of the fill strobe is less than that of the main. This could be accomplished either by a manual intensity level setting on the strobe or by strobe to subject distance. As a guide, for every foot of water strobe light has to penetrate (from strobe to subject), an f/stop of intensity is filtered out. Both strobes therefore could be set to equal intensity but if one was further away from the subject, it's influence would be diminished.

An alternative approach for illuminating macro work may be to position the strobes equidistant on either side of the lens, again varying their intensity to avoid a "flat" image.

Chris Bangs has an excellent tutorial started here. Anyone reading this post should take the time to go back to the beginning of the thread. Another source of information I would recommend comes from Chris Simmons:

http://www.kelpfish.net/strobe.html

regards,
b