Stupid Flash question and AWB

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John P Mulgrew
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p.1 #1 · Stupid Flash question and AWB

I'm sorry for this one and really never gave it much thought. I shoot RAW only and I know there's not much adjusting to do in camera like sharpness and saturation etc.... But you can change the WB I think and when using my 580 EX should I change from AWB to Flash? Or does it really matter.

Dec 02, 2008 at 12:09 PM

freetime101
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p.1 #2 · Stupid Flash question and AWB

If shooting RAW WB doesnt really matter as this can be changed later.

You should set WB to the major light source, ie if shooting in daylight with a little fill flash, daylight is the main light source to wet WB to daylight. If flash is the main light source, set WB to flash etc.

Most flashes are daylight balanced (though still ever so slightly blueish) either daylight or flash will work.

Auto WB does all this for you, though it can vary from shot to shot even if the lighting conditions do not change, so while easier, the results are less reliable.

I personally use AWB and tweak the colour temp later.

If shooting jpeg WB matters, set it manually for the best results.

Sorry if I'm trying to tell you how to suck eggs...

Dec 02, 2008 at 12:43 PM

cgardner
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p.1 #3 · Stupid Flash question and AWB

AWB is never the best choice for the simple reason it recomputes WB with every shot. So if you are at a party with 100 different scenes you'd get 100 different interpretations of the WB based on the reflected light.

A Canon 580ex flash exchanges WB information with the camera in both AWB and Flash modes, but AWB only works effectively if there ore neutral white areas in the shot to use as the benchmark for the WB setting. For example if you point camera and flash at a yellow wall in its attempt to make the brightest thing (i.e. the wall) neutral AWB will skew the color balance the opposite direction towards blue.

If you shoot RAW it really doesn't matter what WB mode you use on camera, but if you want to make batch correction of WB simple you'd want to use the same pre-set for all the shots.

Given the opportunity set custom WB off the flash, especially if you use a diffuser. That can be done anywhere, even at home before or after the event. You can even keep a custom WB shot for your flash / diffuser combo on a spare CF card (like one of those 256K cards from your old camera) and pop it in to set WB.

If you can't do custom WB off a gray card the next best control is to just shoot a gray target with the flash. Do that even if setting custom WB so you can confirm the Custom WB was set correctly.

If you can't do either of the above stick to the Flash preset. The WB might not be perfect, but it will be consistent shot-to-shot and easily batch corrected in post processing.

Chuck

Dec 02, 2008 at 12:52 PM

John P Mulgrew
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p.1 #4 · Stupid Flash question and AWB

Thanks guys and sorry for this question.

Chuck am I understanding you that I can do a custom WB with a gray card here at home while using the flash and then go shoot in a gym and change the WB in ACR later during PP?

Dec 02, 2008 at 05:34 PM

cgardner
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p.1 #5 · Stupid Flash question and AWB

John P Mulgrew wrote:
Thanks guys and sorry for this question.

Chuck am I understanding you that I can do a custom WB with a gray card here at home while using the flash and then go shoot in a gym and change the WB in ACR later during PP?

In a situation like a gym where the ambient light a horrible mercury vapor which cycles with the frequency of the ballast from green/magenta makes any selection of WB problematical if you want to use the ambient light to light the space.

The best WB strategy for mixed lighting situations is avoid it, by either: 1) shooting all ambient with a fast lens (which is a common practice for sports like gymnastics); 2) completely overpowering the ambient with powerful flash which lights up the entire space (which is what the pros do for basketball, hockey, etc. ), or; 3) shooting with a filter on the flash which matches its output to the ambient.

But mercury vapor is impossible to match with a gel on flash because it color shifts. So under that type of lighting the better strategy for normal skin tones would be to set WB to the flash lit foregrounds where the most important action / skin tones are to get them right, even at the expense of making the background off-color.

The overall approach ones take to mixed lighting depends on how one views flash lighting in general. Some think flash isn't "natural" and a generation of FONG O MATIC users have come to equate good flash lighting with lighting up an entire room or arena like an overcast day with uniform light to make the photo seem like what the eye perceived. But that tends to create photos where the foreground gets lose in the clutter of the background.

In most situations I prefer to use indoor flash more like stage lighting, overpowering the ambient and letting the fall off of the flash darken the background progressively eliminating it as a distraction for close-up shots.

When I want more ambience I will bounce my fill flash off the ceiling to lift / and overpower ambient level with flash and use a second off camera flash to selectively highlight areas of the background:

All of those shots have "off color" ambient light, but it is areas which don't affect the perception of the lighting as being "normal".

Picking the ideal solution for any situation is a combination of knowing how the tools work in the purely technical sense and also knowing how those technical results will translate into a perceptual / emotional response to the photos. Viewer emotional reaction will hinge more on correct skin tone / uniform colors in a basketball shot from court side that the fact the people in the background are off color.

Chuck

Dec 02, 2008 at 06:09 PM

John P Mulgrew
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p.1 #6 · Stupid Flash question and AWB

Thank you Chuck for both the info and the time you put into this and all the posts you make. It helps!

Dec 02, 2008 at 06:42 PM

Michael White
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p.1 #7 · Stupid Flash question and AWB

You should always do the WB calibration under the conditions that you are shooting in. Several cheap ways to do it reliably and one or two expensive ways. Cheap ways use a piece of plastic that is dolor correct or event use a piece of broken FL cover or they was a place or two selling cheap WB filters. The expensive way is use an expo disc or get a WilBal chart. Have a stand in hold it shot the shot like you will with the subject then use that shot to calibrate your WB in PP works great if the subjects are coming to you to be shot but is hard to do if you are floating and shooting. The Expo disc is put in front of your lens, point it at the light that will used, take a shot and use that to calibrate your WB you can do this before shooting any shots of subjects even on the move.

Dec 02, 2008 at 07:17 PM

cgardner
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p.1 #8 · Stupid Flash question and AWB

Michael White wrote:
You should always do the WB calibration under the conditions that you are shooting in.

In general yes, but not always. Lighting problems are situational and you need to consider the context of the scene and the perceptual / message goals for the photo.

In mixed ambient / fill flash situations when there are faces in a photo perceptual results are usually better when WB is set at or close to the source illuminating the people in the foreground so skin tones are rendered normally.As mentioned above for mixed lighting like a gym with mercury vapor lighting, doing Custom WB will result the camera trying to split the difference between the two sources with the net result being odd skin tones which would be impossible to balance.

In other cases such as stage lighting gelling the flash with a 1/2 CTO custom WB off the gelled flash or set WB to tungsten will provide the easiest means of a seamless match.

In situations like a scenic of a sunrise or sunsets where you want the camera to retain the same ambience as seen by eye you'd want to use the daylight pre-set, not custom WB set to the warm light. If taking a portrait in front of the subject you'd want to split the difference, retaining the warm glow the sky via a daylight WB pre-set, but also warming up the fill flash on the faces a bit with a warming gel on the flash.

If shooting in RAW the image can be layered and blended to match foreground and background. When that is done its easier to set WB to match the flash lit foreground as the baseline then adjust the WB of a second copy in ACR to match it, combining the two in PS with a mask on the second corrected ambient layer.

Dec 02, 2008 at 07:45 PM


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