Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-29-2009, 06:00 AM   #1
A Proud PENTAXER !!!
fwcetus's Avatar

Join Date: Sep 2006
Location: New England
Posts: 1,075
Histogram Vertical Lines Significance

What do the vertical lines on an in-camera histogram represent? I can see that, if there are three of them, say, dividing the graph into four columns, that the three lines could represent the quarter points between 0 and 255 brightness levels. However, since the main use of the histogram doesn't require knowing what these numbers really are, but simply whether and where the important parts of the curve fit within the histogram boundaries, I'm still left wondering about the lines. Why show them? Anyone?

03-29-2009, 07:31 AM   #2
Veteran Member
alohadave's Avatar

Join Date: Jan 2008
Location: Quincy, MA
Photos: Gallery | Albums
Posts: 2,024
QuoteOriginally posted by fwcetus Quote
What do the vertical lines on an in-camera histogram represent? I can see that, if there are three of them, say, dividing the graph into four columns, that the three lines could represent the quarter points between 0 and 255 brightness levels. However, since the main use of the histogram doesn't require knowing what these numbers really are, but simply whether and where the important parts of the curve fit within the histogram boundaries, I'm still left wondering about the lines. Why show them? Anyone?
They are exactly what you think they are. You can use them to gauge how much you should adjust your exposure. The space between the lines is approximately one stop. So if the right side of the histogram stops at the second to last line, I can increase exposure by one stop with out blowing highlights.
03-29-2009, 10:53 AM   #3
A Proud PENTAXER !!!
fwcetus's Avatar

Join Date: Sep 2006
Location: New England
Posts: 1,075
Original Poster
QuoteOriginally posted by alohadave Quote
They are exactly what you think they are. You can use them to gauge how much you should adjust your exposure. The space between the lines is approximately one stop. So if the right side of the histogram stops at the second to last line, I can increase exposure by one stop with out blowing highlights.
Well, I had thought that it would indeed be useful if the lines (or the columns between the lines) represented stops (or EV values). However, since the histogram on my K20D has four columns, if there were to be a one-to-one correspondence between the lines or columns and sensor EV values, then that would mean the sensor would have a dynamic range of only ~four~ stops. And, I thought that it might have just a bit more than that...
03-29-2009, 11:41 AM   #4
Veteran Member
jeffkrol's Avatar

Join Date: Sep 2006
Location: Wisconsin USA
Photos: Gallery
Posts: 8,434
QuoteOriginally posted by fwcetus Quote
Well, I had thought that it would indeed be useful if the lines (or the columns between the lines) represented stops (or EV values). However, since the histogram on my K20D has four columns, if there were to be a one-to-one correspondence between the lines or columns and sensor EV values, then that would mean the sensor would have a dynamic range of only ~four~ stops. And, I thought that it might have just a bit more than that...
No there not stops, nor are they linear.... There just reference lines with, actually, little significance. Not only are the line steps not equal, the histogram itself is based on the jpg "idea" of the RAW file... . the 5 step histo is generally thought to be in 1 stop increments but this is not necessarily accurate either.
I don't want to downplay their usefulness but it must be put in perspective.
You can sort of calibrate it yourself. Shoot a white or neutral object and see where the hist. peaks. Add +1 EV and shoot again. Add +2 EV and shoot ect....

For instance, testing has shown that one of my digital cameras has a dynamic range of seven stops when shot in JPEG mode with the default settings. However, the same testing shows that a raw image from that camera, that is converted in a raw converter, can contain up to 9.67 stops of dynamic range. In other words, the camera brightness histogram will show a dynamic range that is 2.67 stops smaller than the dynamic range of the converted file. Further analysis shows that the converted file contains 0.67 stops more dynamic range in the highlights and two stops more dynamic range in the shadows than the JPEG file.
http://www.ronbigelow.com/articles/camera-histogram/camera-histogram.htm
kind of not that useful, is it


Last edited by jeffkrol; 03-29-2009 at 12:39 PM.
03-29-2009, 05:21 PM   #5
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
why not measure them. put an f2.8-f22 lens on and set the exposure for F8 .

point at a block wall and with the same shutter speed. go from F2,8 to f22

just did a quick test, each line is just over 1 stop, call it 1 1/3 stops.

Last edited by Lowell Goudge; 03-29-2009 at 06:55 PM.
04-01-2009, 12:55 PM   #6
Inactive Account




Join Date: Dec 2008
Location: Ames, Iowa, USA
Photos: Albums
Posts: 2,965
Thanks Lowell, there's no good substitue for data.

What camera and ISO did you use? This was jpeg output right?

Dave

PS thanks Jeff too - it is good to know the converted raw contains more DR than the straight jpeg. What converter did you use?

Last edited by newarts; 04-01-2009 at 01:00 PM.
04-02-2009, 01:36 PM   #7
Veteran Member
jeffkrol's Avatar

Join Date: Sep 2006
Location: Wisconsin USA
Photos: Gallery
Posts: 8,434
Almost any ;)

I use an old package at home (RAWShoooter) or RAWMagiklite or Pentax's own..
04-02-2009, 01:46 PM   #8
Veteran Member
jeffkrol's Avatar

Join Date: Sep 2006
Location: Wisconsin USA
Photos: Gallery
Posts: 8,434
QuoteOriginally posted by Lowell Goudge Quote
why not measure them. put an f2.8-f22 lens on and set the exposure for F8 .

point at a block wall and with the same shutter speed. go from F2,8 to f22

just did a quick test, each line is just over 1 stop, call it 1 1/3 stops.
Using the k200d and the +/-EV button you can see that the bars are not linear. I'm getting 5+ stops to blowout BUT the -3 only gets me to the last bar. I have a whole quadrant to go. That could have up to or over 2 stops...
7 stops in RAW is probably pretty easy.
Funniest thing is the -3 is about where my D starts... and to tell you the truth it has made it difficult to warm up to this camera (the k200). I still really do like the metering in the D.. odd thing.
I do hope Pentax will eventually do the Nikon thing and allow you to adjust your own base meter value........ PLEASE.....


Last edited by jeffkrol; 04-02-2009 at 02:01 PM.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, dslr, histogram, lines, photography
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
K1000 - Thick black vertical lines on my photos skid2964 Pentax Film SLR Discussion 11 11-27-2009 12:27 PM
Histogram.....what is this? >_< D4rknezz Troubleshooting and Beginner Help 11 10-26-2009 03:16 PM
How to see images vertical images after download as vertical ? netuser Troubleshooting and Beginner Help 8 08-28-2009 03:48 PM
Straightening vertical lines question... sawtooth235 Photo Critique 14 02-08-2009 04:20 PM
Vertical lines still an issue Christian Pentax DSLR Discussion 10 05-21-2007 07:08 AM



All times are GMT -7. The time now is 11:48 PM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top