Question re levels/memory card issue

[ElizK]

I was playing around in Photoshop with some pics from a friend's camera. When I apply an action it brings up the levels box -- which I'd love it if someone were to teach me all about levels, but that's a discussion for another thread, I suppose --, and through several of the pictures there were evenly spaced white lines. The pictures looked fine, and the lines through the levels were not on every picture. Is there a problem with the memory card, or is it something else?

 

[Gdad]

I see that sometimes as well- especially if the levels have already been adjusted once or something that was shot in jpg. I don’t think it is anything to be concerned about. I'm sure some of the more technically proficient types around here could say more though.

 

[boBQuincy]

It is probably not the memory card. Gaps in the levels indicate that there are brightness values missing in the image, usually the result of making adjustments to a JPG. It sounds like the action is adjusting the image beyond the number of levels available, resulting in gaps (a comb-like levels graph).

If the original image does not have gaps then the memory card and image are probably ok. Just for reference, what action is this?

This is one of the best reasons for using RAW, 16x as many (or more) brightness values as JPG!

 

[ElizK]

I'm using the Coffeeshop Perfect Portrait action. I may have adjusted the saturation and/or contrast at that point, and also cropped it. That would have done it?

eta: I've worked with this Photoshop for more than 18 months, hundreds of pictures, and I've never seen that before. Everything I've done has been JPEG. Haven't delved into the RAW realm yet.

 

[boBQuincy]

Yes, adjusting saturation and contrast can leave "holes" in the levels. To check, I opened the same image in JPG and RAW (I usually shoot in RAW + JPG large/fine) and adjusted the brightness to + 100. The JPG had the familiar comb pattern in the levels while the RAW still had a full range of levels (which showed as more detail in the image).

Btw, opening the RAW as 8 bit will not gain us much since that is what JPG is anyway. It takes 16 bits to show the difference although it is not really 16 bits since most cameras save RAW as 12 or 14 bits. Either way it is 16x or 64x as many levels as 8 bit JPG!

 

[ElizK]

Yes, adjusting saturation and contrast can leave "holes" in the levels. To check, I opened the same image in JPG and RAW (I usually shoot in RAW + JPG large/fine) and adjusted the brightness to + 100. The JPG had the familiar comb pattern in the levels while the RAW still had a full range of levels (which showed as more detail in the image).

Btw, opening the RAW as 8 bit will not gain us much since that is what JPG is anyway. It takes 16 bits to show the difference although it is not really 16 bits since most cameras save RAW as 12 or 14 bits. Either way it is 16x or 64x as many levels as 8 bit JPG!

Ok, so to be sure I'm understanding.... it's from OVER adjusting? I had never seen this before, and this past weekend I did my own daughter's senior pics, and saw that combed pattern on my own pics!

 

[boBQuincy]

It is an indication of too much adjustment but not always. Not all scenes have a full complement of levels. Take a photo of a gray card and the levels will show a big spike in the middle with few levels other than that. It just means that there are levels that are not present in the image.

If the original shows no gaps and the edited version does show gaps then that is an indication that the editing has removed some of the levels that were there. It is not always a problem but on subtle gradations (like blue sky) the gaps can sometimes be seen.