White balance and strobes

Hi all

This is a spin off from the Setting White Balance topic. When I was reading through that thread, I wanted to know more about how best to get it right. I am a keen novice in the U/W photography game. I am just past the point and push stage, but not yet up to the DSLR knobs and whistles stage; I have a P+S with an external Inon strobe (although the temptation to DSLR is enormous) and I shoot almost exclusively in blue waters.

So now I have a question in three parts...

PART 1

Really aimed at Alex, but all comers welcome.

I have just read through Alex Mustards article in UwP 42 entitled "Strobes and water colour". My distillation of understanding runs like this....

• P+S cameras assess the white balance of the picture and set it for you.
  
• If you add a cool (Inon) type strobe, the camera will compensate the foreground - which makes the background less blue (more green).
  
• If you add a warm (Subtronic) type strobe, the camera will compensate the foreground - which makes the background more blue (less green).
  
• You can compensate for this with filters, for my Inon, adding a 1/8 CT straw lighting gel.
  

This part of the question is really about filters I suppose. Inon make several types of diffuser for their strobe, essentially white or blue. The blue obviously won't help, but the marketing spiel for their white diffuser says "-0.5 White Diffuser allows the strobe beam angle to widen from a circular 100 degrees to 110 degrees and the quality of light and shadows become softer. " Does this actually change the temperature of the light? Would I need to add a gel to this?

The next parts to the question spring from reading about these diffusers. The spiel for the Inon blue diffusers says "This diffuser is used with compact cameras that tend to give a reddish-yellow hue in your photo. The diffuser renders a more natural color tone because of its blue tint." This suggested to me that P+S cameras get the white balance wrong when using a strobe...so....

PART 2

Manual white balance.

The Setting White Balance topic talked a lot about how to set your manual white balance. You must have removed the camera from Auto mode to do this, so does all the stuff about the camera assessing the white balance and setting it (in PART 1) still apply? Do I need to worry about warming up my Inon strobe if I am setting manual white balance?

Also, in the Setting White Balance topic Cathy Church said "If you have a nice external strobe, you may not have to worry so much about white balance. There is a lot to be said for just setting the white balance on cloudy, and letting your strobe provide wonderful color on the foreground." Well my Ixus has Auto, Daylight, Cloudy, Tungsten, Fluorescent, Fluorescent H, Custom WB settings, so I can set Cloudy. Does the " warming the strobe" apply now?

PART 3

Magic fliters seem to be designed for ambient light and Auto WB. Can you use them with a set WB and a strobe.

Thanks for bearing with me through what seems to have become a convoluted question. I am off to bed now having finished a night shift (which is probably why my brain is tied up in knots over this whole WB thing.)

Cheers

Hal

Hi

I am answering myself here after having done some more reading mostly answering PART 2- kind of self directed learning. Pose a question, refine it, then answer it yourself.

Alex's other article about colour in UwP 31 covers very nicely using Cloudy as a WB setting - basically it makes the subject rich, but muddies the blues.

I still would like to know about gels and filters though

Cheers

Hal

Hi Hal,

I'm pretty new as well, so take whatever follows with a giant grain of salt. My last set up was virtually identical to yours, I just had the Canon SD800 IS. I got some really good results with just underwater mode, auto white balance, and the D2000 strobe set to sttl and f2.8 (the default). I read the same spiel as you, so I bought and used the bluish (-0.5) diffuser which seemed to work well.

Thanks Phil, that's really useful.

I was getting OK results with Underwater mode and Auto WB with the internal strobe, but now I have added the Inon there seems to be so much more to think about. It's a steep learning curve, and I am feeling a little task loaded at present. I am sure it will all settle down once I get comfortable with the rig.

Cheers

Hal

Hi Hal,

Gosh. Quite a bit to get through. My article was about "small differences". It was intended to discuss in detail on of the many aspects that affect water colour in our underwater photos. First up I would say that I would not get too concerned with all of this. The article is about making small differences and is not the first thing to be concerned about. The article is about the difference in blue in these two images. Now looking at the big picture I think that most people would be happy with both images (in terms of colour) and also most people could create either blue in Photoshop. The article was about taking control of this factor in camera.

Most of the articles I write for UWP are aimed at DSLR photographers and tend to be concerned with the finished polish on images.

My distillation of understanding runs like this....

Yep.

their white diffuser says "-0.5 White Diffuser allows the strobe beam angle to widen from a circular 100 degrees to 110 degrees and the quality of light and shadows become softer. " Does this actually change the temperature of the light? Would I need to add a gel to this?

I always shoot the Inons with the "-0.5" white diffuser on. In my tests this makes no signif. difference to colour temp of the light. I mount gels behind this - indeed the diffuser actually holds them in place.

The next parts to the question spring from reading about these diffusers. The spiel for the Inon blue diffusers says "This diffuser is used with compact cameras that tend to give a reddish-yellow hue in your photo. The diffuser renders a more natural color tone because of its blue tint." This suggested to me that P+S cameras get the white balance wrong when using a strobe...so....

I can only presume, like Phil suggests, that this blue strobe filter is designed for use with the camera's underwater mode - basically a mode that ramps up the gain in the red channel. However, underwater modes on digital compacts are very variable. Some work great, others are ineffective. Having one strobe filter for all, would be rather like only making one size of wetsuit.

Cathy Church said "If you have a nice external strobe, you may not have to worry so much about white balance. There is a lot to be said for just setting the white balance on cloudy, and letting your strobe provide wonderful color on the foreground." Well my Ixus has Auto, Daylight, Cloudy, Tungsten, Fluorescent, Fluorescent H, Custom WB settings, so I can set Cloudy. Does the " warming the strobe" apply now?

Cathy's advice is good, but it is aimed at helping new photographers really. Cloudy white balance (usually around 6500K) simply warms up images. It is suggested as a safety net to help photographers who do not get close enough to their subjects - meaning that their images would normally look too blue. Cloudy helps to warm those images up - but will also warm up background blues to a muddy colour too. If you use warmed strobes with cloudy white balance your foreground illumination will look far to warm. Warm + warm + very warm!

This is another of my test shots I took for the article in UWP. In the end I chose not to deal with cloudy white balance in the article, so did not submit this one.

This photo actually shows the same scene as the two shots above. This time with no strobe. See panel 1. I then processed the image at three different WB settings to compare the blues - and I provide crops of those shots. 2 is at the INON setting (5500K) from the flash image above (B), 3 is at the Subtronic setting (4300K) from the flash image above (a), and for comparison 4 is cloudy white balance (6500K). This shows how cloudy WB muddies the blue, slightly.

However, the water is still blue with cloudy WB - which is why it is a useful safety net setting for a beginner. More experienced photographers may want to try and achieve a richer blue.

Magic fliters seem to be designed for ambient light and Auto WB. Can you use them with a set WB and a strobe.

Magic filters are designed for available light photography. It is possible to use them with an appropriate WB and a strobe (well the original Magic filter, anyway), but they were not intended to be used that way.

Anyway, I hope that this helps your understanding. But none of this is essential knowledge for taking photos that you will be pleased with. So don't worry about too much about it. If it looks good to you, it is good!

Alex

I think Alex has done a marvellous job here of explaining how you can adjust (eg.in the RAW converter) to compensate for the colour temperature of your strobe but the effect is to change the colour of the ambient light (in this case the colour of the blue background). It's a take on it that not many people appreciate. Excellent!

Hi

Thanks for the detailed explaination.

I do see that this is a question of subtle changes, and I will take your advice an not worry too much about the details. However I always feel that it is best to learn the right way of doing things, rather than the simplest - it means that I don't have to unlearn bad habits later on (which is even harder than learning the right way in the first place.)

I am learning so much just keeping up with this forum, my deepest thanks to every one who contributes.

Cheers

Hal

Alex, thank you for the more detailed information on in-camera white balance. Up until now, I have been shooting in RAW with Auto WB and adjusting post in PS. My next trip out I was going to try using the "cloudy" WB setting. Then I got thinking...I know trouble.

Does this technique also work in our less than blue (read green) water of Southern California or even in the emerald green waters I've seen in the UK?

Could I set my WB for the strobe, YS-110's, color temp? 5100K with the diffusers.

On my screen, your example above using the Subtronic setting of 4300K is more pleasing to me.

Hi Pat,

I'm not Alex - but perhaps I can help? If you shoot a 5100K strobe and set the WB to 4300 (the color temp of the Subtronic) then your foreground will look very cold/green. The principle is that you set the WB in your converter to be the same as your strobe color temperature - so that foreground looks "right."

The background (water) color just sort of rides along.

If you have a look over on strobist.com (a site you might like to peruse) there is an excellent tutorial about shooting with flash in mixed lighting (tungsten, flourescent, etc). They show you which gels you can use on your flash to account for the mixed lighting situation. Something that is becoming more and more common underwater these days.

Cheers

James

If I've got this right, then the P+S method would be to set a WB that is relatively cool compared to the strobe temperature, say 4200K or "flourescent", to get a good blue background and then rely on the strobe to give a good foreground colour. It's likely to need Photoshop (or whatever) tweaking, and so is more trouble than using a warm strobe and "auto" WB.

This is a brown chessman shot against a white sky with a Nikon strobe and "incandescent" WB. No tweaking in RAW or Photoshop. A long way from perfect, but you may get the idea:

Tim

B)

In other words, despite his eminence, I'm not sure that James is right. I don't think that "cold" (ie blue-er) and "green" belong in the same sentence....

Tim

B)

Yes, you can "tweak" the strobe color by putting a filter on it - so that the foreground will look right.

Here's the article on Strobist that I was referring to:

http://strobist.blogspot.com/2006/03/light...to-correct.html

Cheers

James

...Does this technique also work in our less than blue (read green) water of Southern California or even in the emerald green waters I've seen in the UK?

My understanding from Alex's writing is that you can't turn blue into green or vice versa, but by using a warm strobe (4300K) makes blue into a more pleasing blue, and a cold strobe (5100K) turns green water into a more pleasing green.

Cheers

Dave

Dave, I think I understand what you are saying. Just to clarify, I wasn't trying to turn lead into gold, green into blue. :-) The color is what it is, I just want to get a pleasing and accurate green from our local water, when most of the conversation has been about nice warm blue water. Are the presets the same, or is there a different technique used with different background colors.

I'm going to go read the strobist.com and see what I can glean from that article.

James, thanks! So it makes sense to set WB to the color temp. of your strobe.

It's a take on it that not many people appreciate.

Thanks, John. Although judging by the questions I am not sure I have done such a good job of explaining.

To explain it in a different way. All strobes produce light at a specific colour temp. And as long as we are close to our subject, then the white balance setting required by our camera when shooting wide angle needs to be close to this colour temperature to avoid having a colour cast on our foreground. This is a correction either handled automatically by the camera or manually by us in a RAW converter.

Models of underwater strobes vary in this colour temperature of light they produce - and therefore they vary in the white balance settings that they need to produce a neutral/correct coloured foreground. The article in UWP is about the implication of this for how our background water colour is rendered in our underwater photos.

Basically, in warm strobes (e.g. Ikelites DS125, DS200) produce light at lower Kelvin numbers: 4800K. These strobes require white balance values of approximately this number to produce neutral foreground lighting. As a consequence of this "cooling" of the camera's white balance to around 4800K, blues are rendered more blue.

If we use cool strobes (e.g. Ikelite DS50) which produce light at 5700K these require white balance settings of approximately this value to produce neutral coloured subjects. This "warming" of the image to 5700K means that blues are rendered less blue. However in green water, this slight warming acts to richen greens.

Alex

The color is what it is, I just want to get a pleasing and accurate green from our local water, when most of the conversation has been about nice warm blue water. Are the presets the same, or is there a different technique used with different background colors.

In addition to reading the strobeist article, Pat. You may also want to read my article on underwater photography in Underwater Photography magazine that deals with this affect in both blue water and green water examples. Give that your strobe is fairly close to daylight (5500K - sunny day at noon) then I think that you should get fairly accurate water colours most of the time in most conditions on Auto white balance. If this does not work try setting 5100K.

Alex

Alex, thank you for the more detailed information on in-camera white balance. Up until now, I have been shooting in RAW with Auto WB and adjusting post in PS. My next trip out I was going to try using the "cloudy" WB setting. Then I got thinking...I know trouble.

 

Does this technique also work in our less than blue (read green) water of Southern California or even in the emerald green waters I've seen in the UK?

 

Could I set my WB for the strobe, YS-110's, color temp? 5100K with the diffusers.

 

On my screen, your example above using the Subtronic setting of 4300K is more pleasing to me.

Pat, if you shoot in RAW, you really don't need to worry about the in-camera WB-setting, as it will not affect the look of the final image. But it can off course be nice to have a more 'correct' image in the camera LCD at the time of shooting.

Also worth mentioning - this is for balanced/mixed light shooting. For images completely lit by strobes, it does not apply.

Alex, I would be very interested in seeing the difference (if you have an example) between when using the warming gels behind your 0.5 diifusors and when not.

cheers

Christian

Hey Christian,

I'm sorry to say that I have not sacrificed my dive time to do the back to back tests shots, yet, in the water. I have done the tests on land and I am happy that I am getting the results I want. Of course my land tests prove it to me - but aren't necessarily going to convince others.

On land I have tested 6 or 7 different strobe gels and one can produce light that exactly matches my Subtronics - which would give a result exactly like my first comparison shot above (which was unfiltered INON vs unfiltered Subtronic, but could be unfiltered vs filtered INON).

Actually, I think my Subtronics are a little too warm for me at times (particularly when the water is slightly off blue) - so the gel I will probably settle on (Lee 444) is actually more of a Inon to Ikelite DS125 conversion (5500-4800K). This is the gel I recommended in the article.

I took the comparison shot above when I was running my Cayman workshop in January. Unfortunately I don't have any more teaching weeks until November (usually the best time for test shots as I am not shooting seriously myself). If I get bored, later this week in the Canaries, I might take off a gel during a dive and do some back to back shots. Also I have given some gels to some friends of mine and they might be able to post some examples too, if I fail to do any in Gran Can.

Alex

Hey Christian,

 

I'm sorry to say that I have not sacrificed my dive time to do the back to back tests shots, yet, in the water. I have done the tests on land and I am happy that I am getting the results I want. Of course my land tests prove it to me - but aren't necessarily going to convince others.

 

On land I have tested 6 or 7 different strobe gels and one can produce light that exactly matches my Subtronics - which would give a result exactly like my first comparison shot above (which was unfiltered INON vs unfiltered Subtronic, but could be unfiltered vs filtered INON).

 

Actually, I think my Subtronics are a little too warm for me at times (particularly when the water is slightly off blue) - so the gel I will probably settle on (Lee 444) is actually more of a Inon to Ikelite DS125 conversion (5500-4800K). This is the gel I recommended in the article.

I took the comparison shot above when I was running my Cayman workshop in January. Unfortunately I don't have any more teaching weeks until November (usually the best time for test shots as I am not shooting seriously myself). If I get bored, later this week in the Canaries, I might take off a gel during a dive and do some back to back shots. Also I have given some gels to some friends of mine and they might be able to post some examples too, if I fail to do any in Gran Can.

 

Alex

Thank's Alex. You've already shared a lot of useful information many others would have kept to themselves.

/c

Woohoo...

My first thread to go "hot"

Way to go

Hal