Photoshop Levels - Difficult question

[jasonco]

Hi There,

Is there any way to automate Photoshop CS to bring a group of photos up to a base level? I understand the batch command fine.

For instance, I have a photo that has a great hightone, great midtone, but the lowtone (on the histogram display) starts about a cm in from the far right hand side of the window.

Is there any way to automate photoshop CS to bring this lowtone up to the start of the Histogram curve on every photo regardless of where the photo histogram curve is away from the right hand side of the chart window?

Cheers
Jason

[PacAce]

Give Auto Level a try and see if that's what you're looking for.

[jasonco]

Hey Leo,

No im not after auto levels, I can do that no worries, but it kills all the colours and stuff on some photos (especially the ocean ones). I just want to bring up that lowtone to the start of the histogram line and all my problems are solved!!

Thanks for your reply.
Jason

[G3]

You can record an action, but I'm not sure that it is actually going to give you the results you are looking for if you apply it to every picture you take. Batch processing and actions such as that will work for all pictures taken in a given setting...same lighting, same exposure, etc.. You can also customize the baseline settings of levels (or Curves for that matter).

[jasonco]

Yep I have done that, and as you say, it does the same effect to every photo. So if the Histogram starts 2cm from the far right hand side of the box then the the action that adjusts it for 1cm is applied. it would actually still under expose the picture if only moved 1cm.

Not an easy task....

Jason

[G3]

Well, no....it's not going to underexpose anything. What happens when you move the right hand slider over to the left to the beginning of where your image data actually starts in the Histogram is that Photoshop takes the lightest pixels in the image and turns them white (255). When you move the left hand slider toward the right to the start of your image data on that side, it makes the darkest pixels in the image black. Then you can either lighten or darken the middle tone pixels by moving the center slider left or right.

You can actually set up Auto Levels to adjust the photo the way you want it to by changing it's baseline values.

Try this:
Image>adjustments>levels (or CTL-L)
Click on the Options button
select "find dark & light colors under "Algorithms"
select "snap Neutral Midtones"
click on each swatch under Target Colors & Clipping and enter the RGB values you want to use. To start with, try:
Shadows R=20, G=20, B=20
Midtones R=128, G=128, B=128
Highlights R=240, G=240, B=240
Check the "Save as defaults" checkbox
CLick OK

You can change the values later if you don't like the effect. What you've done now is to change the baseline values that Auto Color uses and set up to run Auto Color when you click Auto in the Levels or Curves dialog boxes. When you are in the Levels dialog box or the Curves dialog box and click on "Auto", it will run Auto Colors and adjust your image using these settings instead of the default.

It also helps tremendously to go into preferences and change your color space to Adobe RGB instead of sRGB, and change your camera to use Adobe RGB also.

[PacAce]

Hey Leo,

No im not after auto levels, I can do that no worries, but it kills all the colours and stuff on some photos (especially the ocean ones). I just want to bring up that lowtone to the start of the histogram line and all my problems are solved!!

Thanks for your reply.
Jason

OK, try this then.

Go into levels and click on Options. In the "Auto Color Correction Options" window, click on "Enhance Monochromatic Contrast" and click OK. Click OK again to get out of levels.

That should leave your colors alone, I think, and hopefully do what you want.

BTW, since this setting is not retained, you'll have to "record" this sequence in your action before running it in batch mode.

[G3]

Hey Leo,

No im not after auto levels, I can do that no worries, but it kills all the colours and stuff on some photos (especially the ocean ones). I just want to bring up that lowtone to the start of the histogram line and all my problems are solved!!

Thanks for your reply.
Jason

OK, try this then.

Go into levels and click on Options. In the "Auto Color Correction Options" window, click on "Enhance Monochromatic Contrast" and click OK. Click OK again to get out of levels.

That should leave your colors alone, I think, and hopefully do what you want.

BTW, since this setting is not retained, you'll have to "record" this sequence in your action before running it in batch mode.

If you click the "Save as Defaults" checkbox, it will be retained.

[maderito]

Go into levels and click on Options. In the "Auto Color Correction Options" window, click on "Enhance Monochromatic Contrast" and click OK. Click OK again to get out of levels.

I believe that the above approach gives you the same result as "auto contrast" which adjusts levels to prevent color shifts.

When applying auto contrast, the luminosity histogram may not spread across all 256 levels, since the operation will not clip individual RGB channels (in order to prevent color shifts).

[PacAce]

If you click the "Save as Defaults" checkbox, it will be retained.

Thanks. I did see that but but I guess it didn't register in my brain.

[PacAce]

I believe that the above approach gives you the same result as "auto contrast" which adjusts levels to prevent color shifts.

When applying auto contrast, the luminosity histogram may not spread across all 256 levels, since the operation will not clip individual RGB channels (in order to prevent color shifts).

I think you're right about that. Thanks for point that out to me.

[jasonco]

Hi Guys,

thanks for your detailed replies. This has fixed about 90% of the photos in the folder!!! Great stuff. Really appreciatte you taking your time out to help me.

Cheers
Jason

[scottbergerphoto]

If you are working on a group of photos that all were shot with the same lighting, you can create a levels adjustment layer in one. Then set your levels for that picture. When you are satisfied click OK. You can then drag that adjustment layer to any photo you want. That way all the pictures in the group will have similiar appearances.
Scott