Brightness vs. Exposure

[Alis]

Could someone, in plain English, explain to me the difference between the effect of Brightness vs. Exposure sliders in LR or just in general the difference between these two.

Thanks,

Sedali

[Colin Southern]

I'm not a Lightroom user, but I do use Adobe Camera RAW extensively - and it's probably the same.

Exposure shifts the values for the entire image up or down whereas brightness is essentially a mid-tone adjustment.

You'd normally adjust exposure first so that your highlights look about right - then adjust brightness to get the midtones where you want them - then fill light to adjust shadows (in assocuation with highlight and shadow clipping points).

Cheers

[rc53]

Lightroom is effectively the same as ACR, and the sliders do as Colin says; exposure is 'like' changing the in-camera settings -- but beware noise in the shadows if you increase exposure; brightness is in the mid-tones.

Alter exposure first, if necessary, in 'combination' with highlight recovery;you may need to alter the pre-set blacks level from standard 5.

Only then fiddle with brightness and contrast.

[Alis]

Thanks a lot, Very helpful. Sedali

[_GUI_]

I am sorry but both Colin and rc53 are not 100% right and I will explain why.

Exposure shifts all levels. In fact it scales all levels by a constant multiplying factor. For instance to push exposure +1EV means doubling all levels in the linear domain (a different factor in the gamma domain).

But Brightness is not just a mid tone control, since it affects the entire image again. The difference of Exposure vs Brightness is that the later preserves the highlights while Exposure will blow them. In chance Brightness makes us loose contrast in the highlights and can lead to some hue changes (not clearly perceivable).

If you are familiar with curves, it can be very clarifying to see how Exposure and Brightness work in terms of a curve (i.e. which curve would perform the same transformation as them). I have developed 3 times the same RAW file with ACR increasing Exposure in the second development, increasing Brightness in the third one, and calculating which curves led from the first development to the other two:

It's easy to see that Brigtness is similar to Exposure for the shadows (a linear scaling), but it starts to behave close to a gamma curve in the highlights, in order to preserve them.
It's just curious that ACR seems to play a bit unfair in the deepest shadows, lifting them a bit more than expected in both processings.

To conclude in plain English, in ACR Brightness is fairly the same as Exposure but preserving the highlights.


Funily, a more academic definition of Brightness means shifting all levels in the image by the same amount of levels, and this is exactly what Photoshop's Brightness do:

Brightness UP in PS

A totally different concept to ACR's Brightness and a tool that is seldom of any use to the photographer. The Exposure control in PS is the same as in ACR.

More info about this in this thread.

[Colin Southern]

"I am sorry but both Colin and rc53 are not 100% right and I will explain why."

*** Shock, horror ***

"Exposure shifts all levels. In fact it scales all levels by a constant multiplying factor."

Hmm - seems pretty close to "Exposure shifts the values for the entire image up or down"

"But Brightness is not just a mid tone control, since it affects the entire image "

You're right of course - but - it's effect is far more pronounced on the mid tones - and as such it's the "go to" tool for mid-tone adjustment, once your clipping points are set - hence the reason I use the term "essentially" (meaning "more or less").

In essence I believe that it's simply changing the gamma - and with clipping points set, raising the brightness has to compress highlights and (because something has to give) expanding the shadows - but, of course, not in a linear way.

Bruce Fraser (photoshop & colour management guru) (and sadly departed) has this to say about Brightness adjustment in Real World Camera RAW with Adobe Photoshop CS2 ...

"Unlike it's image destroying counterpart in Photoshop, Camera RAW's Brightness control is a non-linear adjustment that works very much like the gray input slider in Levels. It lets you redistribute the midtone values without clipping the highlights or shadows ... "

Excellent book by the way (as well as the CS3 version with Jeff Schewe) - absolutely essential for anyone wanting a thorough understanding of RAW files and their processing.

Cheers

[_GUI_]

Well it is true that the Brightness curve has a more pronounced effect in the mid-tones than in the highlights, but it has the same effect in the mid-tones as in the shadows (basically it corresponds to an exposure correction in those two ranges where it is a linear adjustment, as the curves demonstrate. A gamma curve is non-linear in the whole range), that is why I wouldn't consider it a tool specifically issued to adjust the mid-tones since it also adjusts the low tones.

But I understand your point.

BR

PS: and I am glad to agree with the guru about the Brightness control in PS hehe.

[Colin Southern]

I think we're pretty much on the same page here - personally, I use the brightnes control to fix mid-tone issues, but leave shadow issues to the the fill light control (for levels) - or tweak all of them more specifically with the tone curves in ACR for more detailed control.

By the way, I appreciate that the brightness control in photoshop "proper" varies from how the control works in ACR. I was referring to the ACR version since (and correct me if I'm wrong), the control in LR works the same way (LR and ACR use the same engine for RAW), which is what the OP was asking about. Perhaps a bit of an assumption on my behalf, as I've never used LR.


Cheers

[willgoss]

This was discussed before.....my notes from the long discussion.....

Brightness adjustment moves the entire histogram left or right (without compressing or stretching tones, regardless of any resulting shadow/highlight clipping). Using the levels tool, to change the brightness would be equivalent to moving the white or black points left or right by some amount (This should be the same as using the Brightness tool), but moving both equally will not affect the relative tonal relations in between.
Gamma adjustment just redistributes the histogram within a given tonal range (so that it actually compresses highlights to bring out the shadows, or vice versa, without introducing any clipping in either the highlights or the shadows). This adjustment using the Levels Tool is equivalent to moving the midtone slider left or right. Setting the Gamma of an image is one way of adjusting the relative proportions of bright and dark areas.

Increasing Gamma retains contrast and shadows, compressing one of them...
Increasing brightness may lose some of the contrast or shadows……

[agaace]

A very useful thread, thanks all! I just learned a new thing

[Alis]

A very useful thread, thanks all! I just learned a new thing

You're welcome! That's what I do, start useful threads.

Not sure if people are trying to embarras me by uncovering old posts of mine here

But I read it again and realized I did not really understand it the first time!

[Albert]

Hello to all, first timer here. I was browsing the web on the subject and stumbled upon this informative thread. I have read many CiC articles in the past and quite enjoyed them. I'm taking it a step further and registering this time

Question : Why use the Brightness slider when the combination of Exposure + Recovery seemingly does the same thing? Is it because the Brightness slider imposes a gamma curve like compensation while the E+R combo goes linear all the way?
Am I missing something out here?

Cheers,

Albert

[Colin Southern]

Question : Why use the Brightness slider when the combination of Exposure + Recovery seemingly does the same thing?

Hi Albert,

In my opinion anyway, they have the most effect on different parts of the range.

Personally, I use exposure & recovery to control highlights, and brightness to control midtones; I don't need brightness adjustments very often (I prefer to tweak these in a levels layer), but a good example is when I have an image where I have to max-out the fill light control to raise the shadows - but - this may in turn raise the mid-tones too far. In this case lowering the brightness addresses the mid-tone issue, whereas changing exposure and recovery wouldn't work (well it might as far as the midtones are concerned, but at the expense of the highlights).

[Radu Dinu Cordeanu]

GUI and Colin,hi!
This matter in dispute is very interesting not only from technical point of view but before of all I looked for new words into a dictionary.New words like vainglory,selfpride and so on.
Both of you have right because you said the same things with different words.My "math" background inclines to Gui's explanation but Colin's is well too.
Every body could see the effect of brightness and exposure moving the sliders till the image is like they wanted.
To new controversies!
Radu Dinu

PS:till now I didn't know that the words controversy and dispute are like in my "Latin" language,,,

[Ashwin]

Could someone, in plain English, explain to me the difference between the effect of Brightness vs. Exposure sliders in LR or just in general the difference between these two.

Thanks,

Sedali

Thanks Ali,

for putting this query, which even after lapse of one year is providing such a good discussion on the subject.

I don't have TECHNICAL KNOWLEDGE of the subject discussed here. But I know what I have to do to get good presentable Image, and that I am doing by utilising tools of PS

[Donald]

I've just downloaded the trial version of DxO Optics (thanks to Chris' suggestion in Software for editing in RAW) and this thread is now making a lot more sense than it did when I was just operating with Canon's own DPP.

By the way, am impressed with what I'm seeing with DxO (got the film pack plug-in trial downloaded as well to help with the B&W conversions). All I've got to do now is resolve my conscience in abandoning my principles by moving from open source software (I've really struggled to make sense of UF Raw, but I'll still have the GIMP and will stick with it).

[Colin Southern]

All I've got to do now is resolve my conscience in abandoning my principles by moving from open source software

Heck, if DxO would abandon their principles of not supporting DNG as an input file (and change their horrible horrible interface!), I'd probably even use it myself

[Keith Reeder]

All I've got to do now is resolve my conscience in abandoning my principles by moving from open source software (I've really struggled to make sense of UF Raw, but I'll still have the GIMP and will stick with it).

Try Raw Therapee then - a great RAW converter.

[Terry Tedor]

Great thread, very informative.

[Albert]

Hi Albert,

In my opinion anyway, they have the most effect on different parts of the range.

[...]

Thanks Colin!