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01-19-2018, 05:21 PM   #1
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Custom WB with the Fong Diffuser

Ok, so it's Saturday morning here in sunny Australia (not even joking, it's due to hit 42c today :S ), and I'm sipping my coffee and cowering away from the heat whilst youtubing. As one will inevitably do they will come across a Gary Fong vid.

I got to this point in the vid; The Gary Fong Lightsphere Wedding And Event Kit - YouTube

And my ears twitched. "Oh... I have that diffuser and dome!"... "... oh... but I've actually never done custom WB or anything like that before" (with my K-1 or KP), so it got me thinking;

a) Is Gary Fong talking smack right now, about his diffuser being decent for this purpose?

b) I've never done custom WB, don't even know how to do it on my cameras, is there anything/advice to help bruce with this sorta thing? Is it worth it? I mean I typically shoot RAW anyway, and if WB looks weird I play with WB in LR to get something more natural looking. I take it if you make a custom WB for scenario A with the diffuser, leave it on, and then change and move environments you'd need to do it all over again (or flip off it and back to something safer like AWB) otherwise things could go weirdly wrong?

So yeh, basically opening up for a dialogue for discussion about Custom WB. I've only ever really used the camera presets, especially when taking my Lego 'studio' indoor shots, AWB gets the white wrong a fair bit with that I find.

01-19-2018, 05:53 PM   #2
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On my K-1, to select WB options the user presses the left arrow button. Then a selection of WB options is displayed. The Manual and Color Temperature WB options will give you the ability to customize somewhat. I have used Color Temperature and it gives you the ability to adjust the Kelvin levels of WB. I was also able to see the effect of the different settings on my live view screen.

When using Manual Balance, the user can select the part of the scene to be used as a basis for the WB adjustment.

Last edited by C_Jones; 01-19-2018 at 06:32 PM.
01-19-2018, 06:44 PM   #3
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Even with the flash diffuser on, the WB should be similar to that of the flash. If one wishes a value for mixed ambient/flash, setting according to a reference gray card might produce better results (see user guide for manual white balance). Using the dome as in the video is roughly the equivalent and arguably handier.

Another option is to shoot RAW and include a gray card in a test image held by the subject or an assistant using AWB. The gray card may then be used as a reference for adjusting white balance during RAW processing. (In camera white balance only applies to JPEG.)


Steve

P.S. Fong is not talking smack.

Last edited by stevebrot; 01-19-2018 at 07:12 PM.
01-19-2018, 06:55 PM   #4
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QuoteOriginally posted by BruceBanner Quote
AWB gets the white wrong a fair bit with that I find.
Even a custom WB may be "wrong" with mixed light sources and/or many types of fluorescent lighting such that even if the white is "right", the rest of the colors may be badly "wrong". The topic is complex. FWIW, there are people (colorists) who make a living taking care of these details for the motion picture industry and for technical photography. That is the purpose of the ColorChecker panel.*


Steve

* In the Adobe world, such may be used to generate a session-specific profile for import into LR and/or to be embedded in a DNG. Very cool stuff.


Last edited by stevebrot; 01-19-2018 at 07:09 PM.
01-19-2018, 06:56 PM   #5
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While a gray card is nice, a white piece of paper will work just as well. As noted above, just follow directions in the manual on how to do a custom white balance. Center the reference square on your white/gray card and hit OK. It is so simple, and REALLY gets you the right WB.

I do it all the time when I am doing something important.
01-19-2018, 08:42 PM   #6
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QuoteOriginally posted by AstroDave Quote
While a gray card is nice, a white piece of paper will work just as well.
This is true, though care should be taken to avoid clipping in bright light. A clipped pixel has zero color information.* Similarly, care should be taken to not do a custom white balance at high iso where noise may dilute the actual color response information. This last is true for both gray and white cards.


Steve

* If clipped for all three channels (RGB). If clipped for one or two channels the data will be skewed.

Last edited by stevebrot; 01-19-2018 at 08:50 PM.
01-19-2018, 10:43 PM   #7
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QuoteOriginally posted by stevebrot Quote
Even with the flash diffuser on, the WB should be similar to that of the flash. If one wishes a value for mixed ambient/flash, setting according to a reference gray card might produce better results (see user guide for manual white balance). Using the dome as in the video is roughly the equivalent and arguably handier.

Another option is to shoot RAW and include a gray card in a test image held by the subject or an assistant using AWB. The gray card may then be used as a reference for adjusting white balance during RAW processing. (In camera white balance only applies to JPEG.)


Steve

P.S. Fong is not talking smack.
Cheers for that, a couple of points;

You said that In camera white balance only applies to JPEG. I just shot a RAW DNG file inside and set the in camera white balance to Tungsten, the shot was obviously heavily tinted blue. I then took the RAW file off to LR and it still presents as the same heavily tinted blue. So I'm not sure what you're getting at with that comment I bolded, to me it looks like it applies the white balance selected in the camera to the RAW file, but RAW being RAW you can have far better control over such variances to strive to get back to a better white balance if so desired. I was not trusting the image (after the shot was taken) on the back of the LCD of the K-1 as I thought it might be presenting a jpg type preview of the RAW file rather than 'as is', but now that I have taken the RAW file to LR and can see the white balance chosen is still in effect I am a little perplexed to your comment.

2) Yeh I love the Fong, I just jesting

QuoteOriginally posted by AstroDave Quote
While a gray card is nice, a white piece of paper will work just as well. As noted above, just follow directions in the manual on how to do a custom white balance. Center the reference square on your white/gray card and hit OK. It is so simple, and REALLY gets you the right WB.

I do it all the time when I am doing something important.
If I have no piece of paper (or don't want to carry one about, awkward size, gets crushed etc), can I actually use the same white/transparent Fong Diffuser that he shows in the vid, get the model to hold that and use that shot (like he does with the grey one) for post processing?
01-20-2018, 06:49 AM - 3 Likes   #8
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I'm pretty sure the raw file doesn't care about white balance. However Lightroom may read metadata and set initial white balance for the shot to what the camera used for the jpg believing it to be the correct starting point.

01-20-2018, 07:10 AM - 1 Like   #9
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QuoteOriginally posted by BruceBanner Quote
If I have no piece of paper (or don't want to carry one about, awkward size, gets crushed etc), can I actually use the same white/transparent Fong Diffuser that he shows in the vid, get the model to hold that and use that shot (like he does with the grey one) for post processing?
That should work, as will anything else that you deem to be white (or neutral gray). A relatively small piece of paper works, even if wrinkled.

What the custom white balance really does is adjust the relative strength of the R, G, and B channels so that they have the same amplitude (pixel value) within the little square that the camera displays when you put it over your white/gray object. Doing WB in post processing does the same thing, except you get to pick the white/gray area ex post facto.
01-20-2018, 11:16 AM - 1 Like   #10
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QuoteOriginally posted by BruceBanner Quote
You said that In camera white balance only applies to JPEG. I just shot a RAW DNG file inside and set the in camera white balance to Tungsten, the shot was obviously heavily tinted blue. I then took the RAW file off to LR and it still presents as the same heavily tinted blue. So I'm not sure what you're getting at with that comment I bolded, to me it looks like it applies the white balance selected in the camera to the RAW file
Your camera stores the WB/color temperature setting in the makernotes section of the EXIF. LR will read that value and apply it to the RAW development, though not always exactly the same color temp.


Steve

Last edited by stevebrot; 01-20-2018 at 11:26 AM.
01-21-2018, 01:18 AM   #11
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QuoteOriginally posted by AstroDave Quote
While a gray card is nice, a white piece of paper will work just as well. As noted above, just follow directions in the manual on how to do a custom white balance. Center the reference square on your white/gray card and hit OK. It is so simple, and REALLY gets you the right WB.

I do it all the time when I am doing something important.
Bad idea. The white can easily end up 255, 255, 255 whatever tint is present in the light source.

01-21-2018, 01:56 AM   #12
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QuoteOriginally posted by clackers Quote
Bad idea. The white can easily end up 255, 255, 255 whatever tint is present in the light source.
Yeh i don't quite understand. I hear about this 18% Grey thing being talked about all the time, and then Mr Fong mentions his grey dome is 18% grey and can be used in this manner (can it be used on the flash also? why lol... grey light? ), but then folk are saying white is ok... and then Mr Fong once again says you can use the transparent one held over the lens??
01-21-2018, 06:07 AM   #13
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QuoteOriginally posted by BruceBanner Quote
Yeh i don't quite understand. I hear about this 18% Grey thing being talked about all the time, and then Mr Fong mentions his grey dome is 18% grey and can be used in this manner (can it be used on the flash also? why lol... grey light? ), but then folk are saying white is ok... and then Mr Fong once again says you can use the transparent one held over the lens??
If you overexpose even a blue card it can look white. It's called clipping.

White blows easily, black card is useless, so grey is best.
01-21-2018, 07:06 AM   #14
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QuoteOriginally posted by clackers Quote
Bad idea. The white can easily end up 255, 255, 255 whatever tint is present in the light source.
Well, you first have to set the exposure level at something sensible when doing the custom WB - then, check the RGB histogram after you do the WB to check for clipping on your white or gray. I've never clipped it!

QuoteOriginally posted by clackers Quote
White blows easily, black card is useless, so grey is best.
If you set your exposure so that the gray card is in the middle of the histogram, i.e. 50%, you are only a stop away from what you'd get with a completely linear sensor (this is not quite the case for our cameras) and a white card: twice as much exposure, and the gray card will be white (255 in R, G, and B). So, you can blow out the gray card rather easily, too, if you aren't a bit careful with exposure.
01-21-2018, 12:04 PM   #15
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QuoteOriginally posted by AstroDave Quote

If you set your exposure so that the gray card is in the middle of the histogram, i.e. 50%, you are only a stop away from what you'd get with a completely linear sensor (this is not quite the case for our cameras) and a white card: twice as much exposure, and the gray card will be white (255 in R, G, and B). So, you can blow out the gray card rather easily, too, if you aren't a bit careful with exposure.
Dave, who told you that if you expose for 18 percent gray you're just one stop from blowing?



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