Auto Levels vs Auto in Levels

VP
Posted By
Val Patel
Jul 12, 2003
Views
1011
Replies
21
Status
Closed
Hi,

I’m using Photoshop 7.0.1. Why do I get different results when using Auto Levels vs going to Levels and using AUTO? Is there a way to set it up so that identical results are achieved?

Thanks,

Val Patel
Related Tags
auto level vs

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Y
YrbkMgr
Jul 12, 2003
How do you know you are getting different results? The levels dialog gives you access to what is used in AL; they can’t be different.
M
Madsen
Jul 12, 2003
Val Patel wrote:

I’m using Photoshop 7.0.1. Why do I get different results when using Auto Levels vs going to Levels and using AUTO?

It could be that your Auto button in Levels is set to something other than Auto Levels. It’s possible to do that but the default setting is Auto Levels when you press the Auto button in Levels (or in Curves).

Is there a way to set it up so that identical results are achieved?

What happens if you press the Options button in Levels or in Curves? The algoritm should be ‘Enhance Per Channel Contrast’ (which is the same as Auto Levels).

Black: R=0, G=0, B=0.
Midtones: R=128, G=128, B=128.
Highlights: R=255, G=255, B=255.

The shadows should be set to ‘Clip 0.50 %’ and the highlights should be set to ‘Clip 0.50 %’ also.

Maybe you have changed those default settings to something else?

—
Regards
Madsen.
CW
Colin Walls
Jul 12, 2003
I tried this very carefully. I took a reasonable image and wound down the brightness lots, then duplicated. On one copy I did Auto Levels on the other Levels, Auto. If there’s a difference, I’m darned if I can find it. Choosing a couple of spots and zooming in really close [600%], the actual pixels look identical.

So, I’d rephrase Tony’s question: what makes you think they’re different?
Y
YrbkMgr
Jul 12, 2003
Even though you didn’t even acknowledge me, I thought I’d help anyway.

Options by selecting Find Dark & Light Colors and Snap Neutral Midtones.

That’s AutoColor, not Auto Levels.
M
Madsen
Jul 13, 2003
Val Patel wrote:

I changed the Options by selecting Find Dark & Light Colors and Snap Neutral Midtones.

If you choose Image > Adjust > Auto Levels, Auto Levels is what you get, but if you press the Auto button inside the Levels or the Curves dialog box, you’ll get Auto Color, because you’ve changed it to Auto Color by selecting ‘Find Dark & Light Colors’.

—
Regards
Madsen.
Y
YrbkMgr
Jul 13, 2003
I’m invisible. I give.
M
Madsen
Jul 13, 2003
YrbkMgr wrote:

I’m invisible.

I can see you. 🙂

—
Regards
Madsen.
VP
Val Patel
Jul 13, 2003
Thank you all (YrbkMgr, I’m sorry for not mentioning your name in my first reply) for your replies. Are any of the you using the settings I’m using (from Scott Kelby’s book)? What settings give you the best results? Please let me know.

Regards,

Val
S
Stroker
Jul 13, 2003
I believe
Image > Adjust > Auto Levels
works on the composite.

While
Image > Adjust > Levels > Auto
works on the seperate R, G, and B channels.

I think that’s the case.
Shouldn’t be too hard to verify or debunk with some help from Histogram.

edit:
I just did some testing and I’m not getting any difference between the two. Originally I did, but I was using sloppy selections. Once I cleaned up my act, I got the exact same results with both methods.

Copy photo.
On one layer, Image > Ajust > Auto Levels.
On the copy, Image > Ajust > Levels > Auto.
Set the top layer to Difference and you should be looking at pure black. I did this several times with various photos and I got pure black every time.
VP
Val Patel
Jul 13, 2003
Stroker,

I’m glad to hear that you see no difference. Can you please tell me what settings you have in OPtions and Eyedroppers when you go in Levels or Curves?

Thanks,

Val
VP
Val Patel
Jul 13, 2003
Hi,

Is there a way to change the settings of Auto Levels and Auto Contrast and Auto Color individually?

Thanks,

Val
S
Stroker
Jul 13, 2003
Val, all of my stuff is default. At least they should be. Let’s see…

Algorithm = Enchance Per Channel
Snap Neutral Midtones = no
Clip/Clip = 0.5%

Eye Colour Dropper Picker Dohickies and Shadows/Midtones/Highlights: Black = 0,0,0
Gray = 128,128,128
White = 255,255,255

On the rare occassion that I change the colour points, I *always* make it a point to change them back as soon as I’m done. I’ve banged my head too many times because I changed them and then forgot. You know, along the lines of hitting ctrl + h and forgetting about the selection.
VP
Val Patel
Jul 13, 2003
Stroker,

Is there a way to reset all these to original default values?

Thanks,

Val
DM
dave milbut
Jul 13, 2003
it’s in the manual val. try f1. i harly ever use it or i’d tell you right out, but i know i’ve seen it in there…
S
Stroker
Jul 13, 2003
I just do it manually.
Maybe someday I’ll look for the shortcut that Dave mentioned.
M
Madsen
Jul 13, 2003
Val Patel wrote:

Is there a way to reset all these to original default values?

I guess that you have to trash the preference file if you want to reset those settings.

—
Regards
Madsen.
Y
YrbkMgr
Jul 13, 2003
Or set them to the defaults listed in the earler post. You change values, apply them to the image, and you are promted if you want to use the new values as the default.
DM
dave milbut
Jul 13, 2003
click options in the levels or curves dialog. to reset to default, hold the alt key. it changes the cancel key to reset. sheesh!
M
Madsen
Jul 14, 2003
dave milbut wrote:

click options in the levels or curves dialog. to reset to default, hold the alt key. it changes the cancel key to reset. sheesh!

As far as I can see, it changes the settings that you have applied to the histogram inside Levels, but it doesn’t reset the settings behind the Options button inside Levels to the default.

—
Regards
Madsen.
DM
dave milbut
Jul 14, 2003
keep reading…
M
Madsen
Jul 22, 2003
dave milbut wrote:

keep reading…

I’m not sure if it’s me you’re talking to Dave, but if it is, then maybe I have misunderstood something in this thread or elsewhere, but no matter what I do, I can’t reset the settings behind the Options button in Levels or Curves by holding down the Alt key and click on the reset button _if_ I have chosen that my special settings behind the Options button is the default setting (‘Save as defaults’).

I may have misunderstood Val Patel completely but that was what I thought that he had done. I can only reset the settings if I haven’t saved them as defaults.

—
Regards
Madsen.

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