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I got the answer elsewhere. Thought you might want me to post it, so here it is verbatim:
Assuming you’re using CS3 or later: Brightness pins the upper and lower values (shadows and highlights) and adjusts the range between them. Exposure (designed really for HDR work with raw images) takes the strictly linear values in the file and adds or subtracts an equal amount from all of them (just as if you had changed your ISO, shutter or aperture.)
It was a good question. One should be careful about one’s evaluations of other’s efforts! This is, after all, a help/assistance forum. And such comments make one avoid these forums!
In any case, got the better (i.e., more precise, more exact, more knowledgeable, better expressed and more helpful) reply elsewhere. Here it is:
Assuming you’re using CS3 or later: Brightness pins the upper and lower values (shadows and highlights) and adjusts the range between them. Exposure (designed really for HDR work with raw images) takes the strictly linear values in the file and adds or subtracts an equal amount from all of them (just as if you had changed your ISO, shutter or aperture.)
You’re confusing the Original Post with post #1. Post #1 was indeed suspect, and noe it’s proven wrong.
In #1 you said:
Exposure (designed really for HDR work with raw images) takes the strictly linear values in the file and adds or subtracts an equal amount from all of them
That’s what was suspect, and now, confirmed by Chris Cox, WRONG.
You now repeat that in #4.
Exposure (designed really for HDR work with raw images) takes the strictly linear values in the file and adds or subtracts an equal amount from all of them
That, once again, is wrong.
As Chris told you in #2, Exposure does not "add or subtracts" anything. It multiplies.
Exposure does not add or subtract – it multiplies
Now do you see why I didn’t want to start yet another argument with you? B)
Exposure (designed really for HDR work with raw images) takes the strictly linear values in the file and adds or subtracts an equal amount from all of them
Your answer is NOT right. Please see Chris’s response.
When you change your aperture one stop, you either double or halve the exposure. Two stops, and you quadruple or quarter the exposure. You do not add or subtract a fixed value to it.
One should be careful about one’s evaluations of other’s efforts!
Yup, you should be more careful in reading all posts, including your own, and not hurl any invective at those who correct you.
Of course your question was a valid one. It was your alleged "better (i.e., more precise, more exact, more knowledgeable, better expressed and more helpful) reply" spouted in #1 and now astonishingly repeated in #4 that was wrong. Sheesh
First of all, that reply, with which you take issue, is not mine. I said it was not mine in post 1 (which was the second post on this thread) a post I can no longer find.
It is a post from a long time respected member of the Macintosh/Apple community.
Second, however, in the exposure window, a value is chosen which, evidently, is a multiple of the original value(s), as I understand you. But that multiple of the original values, which was evidently arrived at by multiplying those values, is added to the original value when one closes the window. As I understand this.
But what about the distinction that brightness does not affect the brightest and darkest values, but only what is in between?
And, BTW, while my obtuseness, as you seem to think it, may keep you from wanting to discuss with me, even before you knew how I would be discussing, your attitude has a similar effect on me of beiong sorry I even tried using this forum.
It is a post from a long time respected member of the Macintosh/Apple community.
The problem here is that you were disseminating incorrect information, regardless of whether it is first hand or that of a "respected member" of the community.
In reply to the comments about my second post’s explanation of Exposure the author I had quoted replies as follows:
quote That’s really hard to say what the poster meant. Raw image files are linear; film is not, so perhaps he’s saying that multiplication by a single factor produces a linear result (just as doubling the shutter speed halves the exposure.) The new B&C however, is more complex than either option, since it pins the darkest and lightest ends of the scale and bell-curves the rest.
The easiest way to see the difference is to watch the histogram as you apply each adjustment. With exposure, the entire histogram will slide left or right, and the highest and lowest values will fall off the chart. With B&C, the "bell" in the center will move, but you’ll not completely blow out values at the extremes.
This is easy to see by open a chart of color swatches too. End of quote
I feel his original explanation was unfairly jumped on. He obviously knows what he is talking about and is very familiar with the application, which he has been using since it first came out, decades ago.
The amount of correction/change in the exposure option may be, as he says, or might not be, an exact multiple, a la apertures and exposure timings, as expressed numerically in the exposure slideer’s numbers. But the amount brighter or darker that the image becomes when that amount is added to or subtracted from the image is an addition to the image.
But also, neither the members nor your engineer addressed the question, which was the difference between how the birghtness and exposure controls work.
If you notice at www.anstendig.com, I am not exactly an ignoramus about how apertures and exposure work in lenses and cameras. And I knew it back in the 50s, while exercising the then (and still) state of the art in focusing.
My question about the differences was not addressed on this thread. Only some carping about terminology and suspicion of posters, which wording was totally out of place and objectionable.
I don’t like the attitude of this forum and, I suppose, you like me even less.
Thanks for whatever real helpfulness for me was in evidence.
BTW, Since Chris joined Adobe in 1996, it is probably to be surmised that this buddy of mine, who has been a pro photographer as long as I and a respected Apple/Mac expert and programmer since the first Apple computers, has been around using PS for at least as long as Chris and probably a lot longer.
No criticism of Chris. But only offered because you seem to elevate Adobe technicians above other experts.
For goodness sake, Chris Cox writes some (a lot) of the code in Photoshop!
This series of posts by the OP is one of the most absurd I’ve read anywhere. From the get go I knew starting a discussion with the OP would be an exercise in futility and I said so.
This is a forum to correct and help. There is no problem to correct something if it is wrong.
The problem is with the manners on this forum.
The question was a very interesting one for many Photoshop users. This could have been a worthwhile thread for many who didn’t know the difference between the brightness and the exposure options in PS.
The info I posted essentially explained the question. If the exposure did its thing in multiples or simple additions was a distinction to be made. It does not change the basic way the functions work, as explained in that text, which is that exposure changes all values, while brightness keeps the brightest and the darkest values while changing only the tones in between.
Chris’s point was well made. But the distinction did not warrant the unpleasant comments about my post.
Did it ever occur to you to consult the documentation, Mark. Say, the User Guide and/or the Help files?
Exposure command
Adjusts tonality by performing calculations in a linear color space. Exposure is primarily for use in HDR images. See Adjust Exposure for HDR image.
Adjust Exposure for HDR images Comments (0)
The Exposure adjustment is designed for making tonal adjustments to HDR images, but it works with 8‑bit and 16‑bit images. Exposure works by performing calculations in a linear color space (gamma 1.0) rather than the current color space.
1. Do one of the following: *
Click the Exposure icon or an Exposure preset in the Adjustments panel. *
Choose Layer > New Adjustment Layer > Exposure. Note: You can also choose Image > Adjustments > Exposure. But keep in mind that this method makes direct adjustments to the image layer and discards image information. Adjustment layers for 32-bit images are available in Photoshop Extended only. 2. In the Adjustments panel, set any of the following options:
Exposure Adjusts the highlight end of the tonal scale with minimal effect in the extreme shadows.
Offset Darkens the shadows and midtones with minimal effect on the highlights.
Gamma Adjusts the image gamma, using a simple power function. Negative values are mirrored around zero (that is, they remain negative but still get adjusted as if they are positive).
The eyedroppers adjust the luminance values of images (unlike the Levels eyedroppers that affect all color channels). *
The Set Black Point eyedropper sets the Offset, shifting the pixel you click to zero. *
The Set White Point eyedropper sets the Exposure, shifting the point you click to white (1.0 for HDR images). *
The Midtone eyedropper sets the Exposure, making the value you click middle gray.
=== === ===
Apply the Brightness/Contrast adjustment Comments (0)
The Brightness/Contrast adjustment lets you make simple adjustments to the tonal range of an image. Moving the brightness slider to the right increases tonal values and expands image highlights, to the left decreases values and expands shadows. The contrast slider expands or shrinks the overall range of tonal values in the image.
In normal mode, Brightness/Contrast applies proportionate (nonlinear) adjustments to image layer, as with Levels and Curves adjustments. When Use Legacy is selected, Brightness/Contrast simply shifts all pixel values higher or lower when adjusting brightness. Since this can cause clipping or loss of image detail in highlight or shadow areas, using Brightness/Contrast in Legacy mode is not recommended for photographic images (but can be useful for editing masks or scientific imagery). Note: Use Legacy is automatically selected when editing Brightness/Contrast adjustment layers created with previous versions of Photoshop.
1. Do one of the following: *
Click the Brightness/Contrast icon in the Adjustments panel. *
Choose Layer > New Adjustment Layer > Brightness/Contrast. Click OK in the New Layer dialog box. Note: You can also choose Image > Adjustments > Brightness/Contrast. But keep in mind that this method makes direct adjustments to the image layer and discards image information. 2. In the Adjustments panel, drag the sliders to adjust the brightness and contrast.
Dragging to the left decreases the level, and dragging to the right increases it. The number at the right of each slider reflects the brightness or contrast value. Values can range from ‑150 to +150 for Brightness, ‑50 to +100 for Contrast.
What you just supplied is exactly what I had trouble finding.
Why?
Because I have a small macular hole in each eye, which, mercifully, have steadily reduced in size over the 5 or so years I have had them, and still continue to become smaller and less obtrusive (due to disciplines I have mastered and to homeopathic medical help). I do have extreme wide-angle vision, so I can see a whole photograph quite well, with both eyes. But with small text, usually 1 digit is missing in the center. So I easily miss things in Apple’s small help menus or using those menus is difficult, demanding magnifiers, which I do have lots of).
The main fault, for me, of the Apple OS is that text in most text boxes is not readily resized without becoming fuzzy and unsharp, and the ridiculously high res of my 30 monitor displays text at half WYSIWYG size. The help pull down menus and text boxes have text displayed at around 7-8 DPI. Therefore, it can happen that I miss something in those menus…or that it is very hard and tiring to search for some things. Both of which made me ask this question.
Fortunately, my doctor, and I, too, expect further improvement.
But, in the meantime, you are helping a partially sight-impaired person, who, again, mercifully, can see whole monitor-size images, but has trouble with finest small text.
So, I sincerely thank you for taking the trouble to point me to the right help pages and even copy/paste them into your message.
If that had occurred at the beginning, this forum would have received my sincerest and most profuse thanks, and nothing more!
No matter what your motives or manner, you have helped me enormously.
In the future, you might first give people the benefit of the doubt and be kinder to those who annoy you.
Just to be clear, the exposure adjustment in Photoshop is a multiplication — just like changing exposure in a camera. If the document colorspace is not gamma 1.0, then the data has to be converted to gamma 1.0, adjusted, then converted back to the document colorspace. (there are ways to optimize that process, of course)
There is no addition, and no subtraction involved.
And yes, I wrote all the code for the exposure adjustment.
The whole Adobe help info on the subject was posted. So why did it need anything just to be clear?
What I understand from this is that Chris is speaking of how the value is arrived at in the exposure control, which is by multiplication.
BUT, to the user, once that value is arrived at, the control seems to add it to or subtract it from the original image when one clicks on the OK button.
But we can go around about this forever. It was clear from Chris’ first post that the values in Exposure are arrived at through multiplication.
But to the user, both the Exposure and the brightness controls brighten or darken the image a certain amount (however that amount is calculated). The big difference between those two options is what parts of the image each option changes, whether by multiplication or addition or whatever.
That difference in what parts/tones of the image are changed is what most users have to understand. How much either option lightens or darkens those parts of the image that it affects can readily be seen in most of the tones of the image and can thus be chosen on the screen, no matter whether it is arrived at by multiplication or addition, etc. So can the differences in how each option works be seen on screen. But those differences between which tones exposure or brightness change are less usual, so many users miss them and don’t even look for them.
I wouldn’t call the difference between multiplication on the one hand and subtraction/addition on the other a question of "semantics", but of substance.
BUT, to the user, once that value is arrived at, the control seems to add it to or subtract it from the original image when one clicks on the OK button.
That would depend on whether the user knows the difference and whether he’s paying attention or not, whether he knows what a histogram tells him or not, how capable and accurately calibrated his monitor is, and how keen his tonal perception is. Personally, I’d never characterize it the way you do ("the control seems to add it to or subtract it"), Mark.
Look at the histogram while you move the Brightness and Exposure controls back and forth.
no matter whether it is arrived at by multiplication or addition
I disagree with you there too, for the reason stated in the first paragraph of this post.
If you take such a careless attitude about the definitions, I wonder what prompted you to post inquiring about the difference between the two functions in the first place. (Just a rhetorical question that requires no answer.) 🙂
Unfortunately, Mark – this group is often all about semantics as that provides a greater opportunity for debate. It’s assumed that everyone who is not a regular here is an idiot.
Yes, this is a pretty stupid debate. It’s a perfectly acceptable statement to say when you increase light intensity by one stop, you have added light to the scene, despite the fact that the light has doubled through a principle of magnification. Never once have I muttered to myself, "I need to multiply the light."
Likewise, when you drag the exposure slider in Photoshop, you are adding (increasing), or subtracting (decreasing), the brightness levels, even though multiplication/division is happening under the hood.
Notice the + (plus sign) and – (minus sign), that appear when you drag the sliders off the zero point?
I can only surmise that Chris feels the need for "clarification" because he writes code and mainly deals in principle and theory, which of course, is often much different than real world photography.
I had pretty much given up, but now realize that mainly one person was making all the noise.
Good to know that there is someone here who reads objectively and not subjective-emotionally.
It was good that Chris pointed out the differences in the calculation of the lighter or darker adjustments. That was an added point to be made, which, in reality, did not contradict anything else.
It was someone else who said that post number 1 was suspect…..a wording out of place here.
If something is wrong, simply nicely point it out and correct it. But saying something is suspicious is a whole different all game. No one here is, in my impression, trying to purposely do anything suspicious.
But the whole thing wrong is that these are not discussion forums. They are help forums that are meant to complement the Adobe Tech support options.
All that is needed is to give the answers if one knows them and possibly explain resulting questions. Not to discuss.
But some here seem to have the need to discuss things, which is better done elsewhere, IMO. But one can get addicted to discussing.
someone here who reads objectively and not subjective-emotionally
But the whole thing wrong is that these are not discussion forums. They are help forums that are meant to complement the Adobe Tech support options.
Although I sense your frustration here, these are indeed discussions that we generally provide, not as formatted user manual text content, with each participant providing his or her viewpoint.
But that said, the accuracy of particular words (addition/subtraction vs multiplication/division) would be required to properly complement Adobe support. And that is an objective, not subjective response.
The best solution for you to understand the differences between adjusting exposure and brightness may be to take several different good, wide-range images. Make duplicates of each. And then make side-by-side comparisons using exposure adjustments on one set; and brightness on the other. Scrutinize what happens to the shadow areas, highlight areas and middle tones. The old saw, "a picture is worth a thousand words" works well here.
That has long since been done, right after the first reply from elsewhere.
And that gets to the beginning of what has transpired: namely that I did not get a reply with explanation here before it came from elsewhere. So, to be considerate, so I thought, I posted that reply here.
After that post some posts became nasty, calling that post suspect and being argumentative and annoyed-seeming, rather than just pleasant and helpful.
I felt the attitude was because I mentioned I had not gotten the reply here.
And that remains my impression.
It is only these last posts that some here have really been genuinely only interested in being helpful.
Sorry, but that is my impression.
I appreciate your kind comments and suggestion. Just remember that the person who first explained the issue elsewhere already suggested viewing the differences in PS and how.
Every time it is ended, someone adds to it something that is right, but needs, IMO, a bit of explanation. Or Ramon has to trump it and prove that he is right about something.
And, my dear Adobe forums colleagues, there is a simple reason why you do not have to take Ramon seriously, or bother with this thread if you think it is ended….which it was long ago:
And that reason is that you simply do not have to read it. I haven’t read a single other thread on these forums in this time period. I do not have that compulsion.
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