Jump to content


Photo
- - - - -

Photoshop Histograms Inaccurate


  • Please log in to reply
6 replies to this topic

#1 Kasey

Kasey

    Great Hammerhead

  • Member
  • PipPipPipPip
  • 709 posts
  • Location:USVI

Posted 04 November 2002 - 03:24 PM

I've felt that the histograms of underwater photos in photoshop tend to judge properly exposed images to be underexposed. I expect this in blue-water scenes, but even in macro scenes I've found this to be the case. Only in well-exposed bottom scenes with lots of sand (flounders, sea cucumbers, etc.) have I found that the histogram successfully judges exposure. Any comments from other PS users? I use PS 7 on Mac OSX.

Kasey
Seacam F100;D2x; 60mm;105mm;16mm;17-35; 10.5mm;12-24mm
Sea & Sea strobes
www.underthecaribbean.com

#2 gothamboy2000

gothamboy2000

    Clownfish

  • Member
  • Pip
  • 22 posts

Posted 02 December 2002 - 08:08 PM

The histogram is, after all, just data. Population of each of the RGB channels is simply that. A histogram is not weighted based on the perceptual values of those colors. (A properly exposed orange sunset will look brighter than a properly exposed blue water scene.)

It's interesting that you used the word "Judges" when explaining the histogram. Naturally, Photoshop doesn't really "judge" the colors at all.

Daniel Brown
Sr. Evangelist
Adobe Systems Inc.
danielb@adobe.com
http://www.adobeevangelists.com

#3 snoack

snoack

    Wolf Eel

  • Member
  • PipPip
  • 187 posts
  • Location:Munich, Germany

Posted 03 December 2002 - 01:01 AM

Kasey,

although the histograms can tell me a lot about what's wrong with a photo, i never use them to judge correct exposure. i usually notice over/underexposure when i simply look at the photo :blink:

Sabine

#4 james

james

    The Engineer

  • Super Mod
  • 9968 posts
  • Location:Houston TX

Posted 03 December 2002 - 06:00 AM

Daniel,

In case I haven't said this before, welcome to Wetpixel!!!!

Our primary tools here are:

1) Digital Camera
2) Underwater Housing
3) Adobe Photoshop!!!!!!!!

I don't know where most of us CCD and CMOS shooters would be without the Unsharp Mask!

Your comments and insight are truly appreciated, so please stick around.

Cheers
James Wiseman
www.reefpix.org
Canon 1DsMkIII - Seacam Housing
Dual Ikelite Strobes
Photo site - www.reefpix.org

#5 gothamboy2000

gothamboy2000

    Clownfish

  • Member
  • Pip
  • 22 posts

Posted 03 December 2002 - 10:16 AM

Thanks Jamesw!

Good to be here... My wife and I got hooked a year ago speaking at the underwater shootout events.

(http://www.theshootout.org)

We just got back from Bonaire and the combination of diving and Photoshop are still on our minds.

As for my comments, glad to know they might be of some help. If there's ever a really sticky question, I can always walk up a flight of stairs and ask the software engineers. So even if I don't know the answer, I can certainly find someone who does.

I'll certainly pass along my Photoshop tips in exchange for some idea as to how you guys get sea life to pose for those amazing pictures!

Cheers!

Daniel Brown
Sr Evangelist > Adobe Systems Inc.
danielb@adobe.com
www.adobeevangelists.com

#6 james

james

    The Engineer

  • Super Mod
  • 9968 posts
  • Location:Houston TX

Posted 03 December 2002 - 11:26 AM

Hi Daniel,

I just got back from a day dive trip where I shot three dives @ 76 fuji RAW images apiece. Information overload!!!!!!

If you guys can make a photoshop plugin for fuji RAF files that works as well or better than Mike Chaney's Qimage Pro, I will buy it in a heartbeat.

Right now my workflow is something like this:

Burn all my RAW's to CD as an archive.

Open the Fuji image browser and pick the RAW files from my hard disk that I want to convert, then convert them as a batch using their Hyperutility LE fuji software.

Open the 12 megapixel TIFF's in Photoshop, then adjust levels, then curves, then USM.

Drop those all in a file then use the Web Image Gallery feature to do batch resizing (images to 600 pixels wide) and thumbnailing.

USM AGAIN on the 600 pixel images and then up to my website.

Man, that is time consuming.

So what did you think of the DSLR shooters at the Bonaire Shootout? Is their output good enough for publication? I think it is but some ppl still think it is up for debate.

What would you like to know about UW photography technique? We can SURELY trade tips.

Cheers
James
Canon 1DsMkIII - Seacam Housing
Dual Ikelite Strobes
Photo site - www.reefpix.org

#7 gothamboy2000

gothamboy2000

    Clownfish

  • Member
  • Pip
  • 22 posts

Posted 05 December 2002 - 02:22 PM

Hi again James,

We certainly understand your pain (along with that of everyone who uses higher-end cameras capable of raw formats). Again, can't comment much other than what the press release said and what my Julieanne Kost demoed at the keynote at Photo Plus East.

I hear the distinct sound of salivating going on... :)

Daniel Brown > Adobe Systems Inc.