You need to click on a solid, try the Godox writing on the softbox.
White Balance Card
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Archibald
Well-known member
It doesn't matter where I click. The dropper affects the WB for the entire picture. The problem is that there is a hue difference between the blacks. That can't be fixed by the eyedropper or any editing that affects the whole picture.
The Godox lettering is neutral in the first image.
I'm pretty sure that I'm seeing color rendering issues here. Colors that look the same to the eye can have different spectral properties, and can therefore appear differently to the sensor. What I'm finding surprising is the extent of it in my experience, and that apparently nobody else sees it in their work.
Archibald
Well-known member
I am pursuing some ideas on what is causing what I'm seeing. However, it is OT to this thread, except to say that I find WB cards to be unhelpful because of the unexpected colors.
I could start a new thread once I have some explanations, if anyone would find that useful.
I could start a new thread once I have some explanations, if anyone would find that useful.
For laughs, I downloaded your last image, clicked with the dropper on the Godox letters and that made the background and the softbox neutral on my screen. If it's not working for you, maybe your computer screen is off calibration.
Archibald
Well-known member
Global adjustments can't do selective adjustments.
As I see it there is no reason to use the eyedropper on the textured backdrop. It is not guaranteed to be neutral. It's better to shoot the white balance card under the same light, use the eyedropper on the white balance card, and apply those same temperature and tint settings to the actual shot. Also make sure you have a white balance card and not an exposure gray card.
Archibald
Well-known member
Since we're continuing...
Thanks, Nimi, I appreciate you taking an interest. But remember that you can't make local adjustments with global adjustments. Global includes things like monitor settings, WB, light color, temp, tint, what have you.
I think Optical Brightening Agents are playing a role here. Optical brighteners are colorless dyes that are added to many products including paper. They make paper look whiter by generating a small blue glow from incident ultraviolet light. That bluishness cancels out the natural yellowness of paper, and allows manufacturers to claim extreme whiteness levels. When you go into some bars that have black light, those OBAs light up in some clothing and some paper.
I don't have a UV light handy to do direct testing, but I did do a comparison of light sources - Godox modified flash vs incandescent. I suppose the flashes have a small amount of UV, whereas incandescent will be very poor in UV.
We were talking about blacks before, but I'm switching to whites here. I hope that doesn't confuse the issue too much. But I often observe color shifts in whites too.
Here is a comparison with the two light sources. I used the eye dropper on both photos between the doll and the chicken.
I suspect my black textured backdrop was printed on material containing optical brighteners, and that is causing it to shift blue.
Thanks, Nimi, I appreciate you taking an interest. But remember that you can't make local adjustments with global adjustments. Global includes things like monitor settings, WB, light color, temp, tint, what have you.
I think Optical Brightening Agents are playing a role here. Optical brighteners are colorless dyes that are added to many products including paper. They make paper look whiter by generating a small blue glow from incident ultraviolet light. That bluishness cancels out the natural yellowness of paper, and allows manufacturers to claim extreme whiteness levels. When you go into some bars that have black light, those OBAs light up in some clothing and some paper.
I don't have a UV light handy to do direct testing, but I did do a comparison of light sources - Godox modified flash vs incandescent. I suppose the flashes have a small amount of UV, whereas incandescent will be very poor in UV.
We were talking about blacks before, but I'm switching to whites here. I hope that doesn't confuse the issue too much. But I often observe color shifts in whites too.
Here is a comparison with the two light sources. I used the eye dropper on both photos between the doll and the chicken.
You can only see EXIF info for this image if you are logged in.
I suspect my black textured backdrop was printed on material containing optical brighteners, and that is causing it to shift blue.
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beano
Member
Hello, yes, correct. As one that is involved in provided Quality Control Systems to Pulp&Paper Industry (Valmet Automation), I know the process-control part rather well.
On top of the OBA, which is basically a ‘sheet brightness enhancer’, there often is basic, or full color-control, involved. Advanced color-control will include online monitoring and shade/color-control via typically a mix of 2 or 3 dyes, green, blue, red.
Customers will replenish dye-batches from the likes of BASF, for example, and the online color-sensor will be calibrated against standard Lab principles, to ensure color-accuracy across dye-batches. There also is a standard calibrated white-tile to ensure brightness is accurate.
Anyway, you will always find color-variation in paper, depending on the calibration principles, sensor accuracy and repeatability, dye-concentrations, and others. It’s not uncommon to find greens, yellows, blues, out there. Blue often appears the brightest, but to see these differences, paper-sheets must be compared side-side.
Anyway, if you want to calibrate against pure white, you might be able to get hold of a standard white color-sensor calibration tile, these will hold their original color and brightness for many years. But, they are expensive.
Pardon the verbiage.
If you think of a color wheel or just rainbow colors, Roy G. Biv, then the color rendering issues might make sense in terms of white balance. If a photo has a color cast to the point where what should be neutral is going toward the cool- greenish or bluish, then all colors will be cooler. Yellows that should be banana yellow might be lemon yellow. Reds that should be Ferrari red might lean toward magenta or purple. Greens that should be grass green will be more blue green. Everything will lean cool. The opposite will happen when there is a warm cast to the white balance. Reds will be orangey, blues will lean greener and so on. Sometimes this is desirable, but I find it useful to find neutral and then make the artistic decision to lean it warm or cool. Sunrises for example would look off if neutral.
Archibald
Well-known member
Bill, you appear to be talking about color balance. Color balance is not the same as color rendering.
I was talking about white balance, where the color cast of a non neutral light skews the "real" colors. But is all inter-related. One can hover the cursor over an area before and after white balance and see the RGB change.
That makes sense, confirming to me what has been said, that the practice of using copy paper as a white balance target is not a good idea, at least outdoors.
spamalot1950
New member
Just a wee bit curious: has anyone here ever used an Expodisc 2.0? I've had one in my camera bag for years to use in lieu of a grey card, and I've never been disappointed by the results.
I've not used one but they seem solid. Similar to an incident colorimeter for that one purpose but a lot cheaper. The only caveat is the usual one, that the camera has to be in the same light as the subject pointing at the light. If the subject is in shadow but you are not or vice versa you have to take notice and adapt. Do you find it reliable?
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Terps
New member
I’ve had a ColorChecker Passport for many years now. It states on the Passport that “For maximum performance, ColorChecker Passport should be replaced within 2 years from initial use.”
I don’t do color critical studio work, but when I do shoot people in difficult light I do like to use the Passport to get the white balance right. By difficult light I mean shooting in a hockey arena or in indoor mixed light. I do treat the Passport with care and only expose it to light when taking the initial shot and then closing it so as not to let light “bleach” the colors. It still seems to work just fine, but then again I don’t have a new Passport to compare it to.
Any thoughts or experience with using older Passports?
I do realize the statement says “For maximum performance”, and “should be replaced” and not “discard after 2 years.”
I don’t do color critical studio work, but when I do shoot people in difficult light I do like to use the Passport to get the white balance right. By difficult light I mean shooting in a hockey arena or in indoor mixed light. I do treat the Passport with care and only expose it to light when taking the initial shot and then closing it so as not to let light “bleach” the colors. It still seems to work just fine, but then again I don’t have a new Passport to compare it to.
Any thoughts or experience with using older Passports?
I do realize the statement says “For maximum performance”, and “should be replaced” and not “discard after 2 years.”
spamalot1950
New member
The only instance in which I had trouble was photographing an outdoor reception on a partially shaded lawn. Essentially, I was just taking candid snapshoots. I learned from experience that the camera's automatic settings do a more credible job then. Otherwise, the WB needs to be reset constantly. When doing indoor stills, or shooting anywhere that the light source is fluorescent, the Expodisc is quite good.