Don't use brightness / contrast to adjust brightness / contrast


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#1
Came across this advice from PHOTOSHOP COLOR CORRECTION by Michael Kieran.

I thought it was interesting, especially for someone like me who, in the past, tried to learn Photoshop the DIY way by just clicking here and there to see what happens.

The reason is this: “Brightness / contrast will definitely, positively, certainly, undoubtedly throw away valuable tonal information from your images.”

eg, if increase brightness by +15, then any pixel with a brightness value of 240 and above will become the same colour, ie pure white, at 255. So you lose all the details in the highlight.

Adding contrast, according to the author, is even worse as it pushes out the highlights and shadows.

Author recommends using levels and curves to adjust instead.

So alamak, I have to revisit all my pixs and re-adjust them. Serves me right for trying to DIY.
 

user111

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#2
agree that curves is a more subtle method
 

jopel

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#3
RichardSeah said:
Author recommends using levels and curves to adjust instead.
Like Brigthness/Contrast, level will also do harm to your digital file.
Use curve with an adjustment layer
 

r52lanc

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#4
Increase brightness moves histogram to the right.
Decrease brightness moves histogram to the left.
Increase contrast widens the histogram.
Decrease contrast narrows the histogram.

These are important steps in any digital workflow. Don't listen to these self-proclaimed gurus....... really morons in disguise.

BTW, Brightness/Contrast can be added as an adjustment layer. Curves is simply brightness and contrast combined in a single tool. You can ruin your photo with curves also. Always keep the histogram visible during your editing!
 

yanyewkay

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#5
r52lanc said:
Increase brightness moves histogram to the right.
Decrease brightness moves histogram to the left.
Increase contrast widens the histogram.
Decrease contrast narrows the histogram.

These are important steps in any digital workflow. Don't listen to these self-proclaimed gurus....... really morons in disguise.

BTW, Brightness/Contrast can be added as an adjustment layer. Curves is simply brightness and contrast combined in a single tool. You can ruin your photo with curves also. Always keep the histogram visible during your editing!
:thumbsup: agreed.

there's absolutely nothing wrong with DIY learning, but must learn correctly. Getting a simple book or magazines to read is good. Just don't believe everything they say when some try to bring down the methods of others. It doesn't matter which method you use. As long as the end results shows. I am a DIY learner and still learning.
 

sexyguy

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#6
My little suggestion... Always make a backup of the original file... Play to your hearts content with the replicate copy.... ;)
 

Venom81

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#7
sexyguy said:
My little suggestion... Always make a backup of the original file... Play to your hearts content with the replicate copy.... ;)
Best tip. Back up. :thumbsup:
 

roygoh

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#8
r52lanc said:
Increase brightness moves histogram to the right.
Decrease brightness moves histogram to the left.
Increase contrast widens the histogram.
Decrease contrast narrows the histogram.
To me, the problem with using Brightness/Contrast is that it adjusts Brightness and Contrast (and for that matter, colour correction) separately. From my experience, in most cases, by the time brightness is adjusted to the correct level, contrast is off, and then by the time contrast is adjusted to the correct level, there will be blown out highlights or "blacked outed" shadows. As such there is always a few rounds of iteration before things look correct.

Plus, since Brightness/Contrast applies the same effect to all channels, if colour correction is needed then it just complicates the entire workflow. Last but not least, in Brightness/Contrast adjustment the histogram is not displayed to show the effects of the adjustments made, so there is really a lack of control.

This is probably why the author of the book quoted by RichardSeah made the recommendation against using Brightness/Control.

I prefer to use Levels most of the time and Curves in really difficult situations. With the help of the eyedropper tool and playing with the histogram directly I can correct brightness, contrast and do colour correction at the same time, without the need for a few rounds of iteration.


r52lanc said:
These are important steps in any digital workflow. Don't listen to these self-proclaimed gurus....... really morons in disguise.
Agree that histogram manipulation is an important step in digital workflow, but that is not the argument here. The point is Brightness/Contrast adjustment in Photoshop is not as effective as adjusting Levels or Curves (if one knows what he/she is doing).

BTW...don't mean to offend you, but dismissing someone as "moron in disguise" make you sound like a "self proclaimed guru" also... ;)


r52lanc said:
BTW, Brightness/Contrast can be added as an adjustment layer. Curves is simply brightness and contrast combined in a single tool. You can ruin your photo with curves also. Always keep the histogram visible during your editing!
As explained above, there key benefit of using Level/Curves (to me at least) is that it combined brightness/contrast as well as colour correction in a single tool. So far I am not aware of how the histogram can be displayed in real time while using Brightness/Contrast on Photoshop (5.0 LE, 7). If that can be done then it makes Brightness/Contrast significantly more effective then it is now. In fact it would be great if the histogram can be displayed when doing curves also.

- Roy
 

#9
r52lanc said:
Increase brightness moves histogram to the right.
Decrease brightness moves histogram to the left.
Increase contrast widens the histogram.
Decrease contrast narrows the histogram.
This is good way of explaining it. Thanks.

But won't this mean that if increase brightness then those at the extreme right of historgram will all be combined together?

So if increase by, say, +30 [which I have done before when scanning came back very dark] then those pixels previously from 225 to 255 now all become 255 and all look alike?

Likewise if already have good spread across entire histogram, increase contrast will push some outside the range? But if original pix only have pixels in the middle of histogram, then I guess it is ok?

The book I read was quite convincing on this point.
Anyway it got me -- a newbie -- to explore levels and curves further rather than rely on easy way of adjusting brightness and contrast.

It also got me thinking that perhaps levels and curves are more than brightness and contrast combined.

And thanks for all other discussions and inputs.
 

jopel

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#10
roygoh said:
As explained above, there key benefit of using Level/Curves (to me at least) is that it combined brightness/contrast as well as colour correction in a single tool. So far I am not aware of how the histogram can be displayed in real time while using Brightness/Contrast on Photoshop (5.0 LE, 7). If that can be done then it makes Brightness/Contrast significantly more effective then it is now. In fact it would be great if the histogram can be displayed when doing curves also.
- Roy
In PSCS you can have a realtime histogram in all the channel for all the adjustment tools. :thumbsup:

BTW the level tool can be apply to a 16bits digital image without causing serious banding as the 8bits image. :think:
 

jopel

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#11
RichardSeah said:
The book I read was quite convincing on this point.
Anyway it got me -- a newbie -- to explore levels and curves further rather than rely on easy way of adjusting brightness and contrast.
Richard, you are on the right track into the world of digital imaging. :thumbsup:
 

fengwei

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#13
Witness said:
juz do wat works lo,.....i use both curves and the brightness/contrast to get wat i want...
I'm with you on this. It's just a piece of software, and it's your photo. Do whatever you like, the way you like. And if you like the final result, that's good lah. Actually brightness/contrast adjustment can achieve some special effect sometimes.

But for me, normally I don't need to adjust brightness/contrast. My work flow is very simple (for jpg):

1. Crop if needed
2. Auto Level. Most time it works. But if doesn't satisfy me, undo it, then adjust level manually
3. Adjust Curves a little bit if not satisfied with the level adjusting result
4. Adjust Saturation if needed
5. Resize for Web
6. USM and Sign

Each pic needs less than 1 min processing time, unless I really wanna achieve some special effect.

I only backup what I want to or might print out, others just keep the web posted versions.

Cheers!
 

melnjes

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#15
Pro Image said:
When your exposure is spot on, you do not even need to use the B and C thingy. :sticktong
Second that.
 

roygoh

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#16
Pro Image said:
When your exposure is spot on, you do not even need to use the B and C thingy. :sticktong
Agree in principle, but in practice how to get spot on exposure for every shot?

In contrasty situations or when the lighting is bipolar in nature (some region very bright and some region very dark), it is either difficult or impossibe to get an exposure setting that is considered "spot on". One example that I have experienced is shooting in snow covered landscape. If there are objects of interest that is considerable dimmer than the snow and using fill flash is impractical than the exposure becomes bipolar.

Also, there will be situations where the photographer does not have enough time to do proper metering and exposure compensation for every single shot.

In such cases I usually set -0.3 EV to reduce chances of blown out highlights, then I use levels and curves to bring out the necessary details. Of course under extreme conditions the noise level in the shadows will be too high to be useful, but I am trying to demonstrate that a "spot on" exposure is not always possible.
 

Uplift

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#17
Richard, your intentions are good, but I humbly suggest that it'll be better if you spend some time UNDERSTANDING the various manipulation TOOLS that PShop offers.

The comment that “Brightness / contrast will definitely, positively, certainly, undoubtedly throw away valuable tonal information from your images” is true for most adjustments. Eg. apply USM and you'll be throwing away tonal info too. Use Levels or Curves improperly and you'll end up with the same results.

If I were to author a PShop book, I'll say this...
B/C is a very 'blunt' and restrictive way of manipulating an image. Contrast is adjusted through EQUAL manipulation of black and white points. You can't control them independently, whereas Levels and Curves allow you to do so. Brightness is an overall adjustment.

The Levels function allows you to control the black and white points independently. Offering much more control. Brightness is not an overall adjustment, but an adjustment of the gamma (say, mid) level.

Curves, the most 'powerful' function allows you adjust every point independently.

In the end, it's how you understand and use these tools effectively.

Anyway, it's because of the flexibility and DEGREE of CONTROL offered by Levels and Curves that most users prefer them.

Hope this helps, mate :)
 

EdOkH

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#18
i prefer the selective colour control as this gives me more control over the respective colours...

:)
 

r52lanc

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#19
Uplift said:
The comment that “Brightness / contrast will definitely, positively, certainly, undoubtedly throw away valuable tonal information from your images” is true for most adjustments.
No, lah! If there is room on the right/left of the histogram, you can safely use B/C without any damage. In fact, much improvement. The goal is to get rid of dead pixels at both sides of the histogram and... to center the histogram.

When you move the left/right sliders in Levels, you are in fact doing the same thing as adjusting the contrast in B/C.

When you increase gamma, you simultaneously reduce contrast. That's why curves is useful. You can increase/decrease gamma and contrast at the same time. :bigeyes:

I suggest using curves for polishing at the end of a workflow.
 

Uplift

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#20
Hence the GENERAL statement that it "is true for MOST adjustments," bro., and not ALL adjustments (with attendant assumptions of course) ;)

I mean, although it can be easily done, I'm not about to shoot down your GENERAL statement...
r52lanc said:
The goal is to get rid of dead pixels at both sides of the histogram and... to center the histogram.
...cos I do understand the general direction that you're driving at! :D

Peace! Out
 

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