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11-21-2008, 12:18 PM   #1
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D-Range - A Technical View

I've had a little free time latley and decided to jump into measurbating (oh no!). I tried a personal test yesterday to see exactly what D-Range did and if I wanted to keep it on or leave it off. I figured out this morning that what I did yesterday was flawed. I started scowering the net and came across a program called Imatest which offered 20 free tests in its trial. It seems like a wonderful program although the only part I used was the dynamic range/noise portion. I set up my studio and within an hour or so I came up with some results. Before I share, I want to let you know the setup:

Camera: K200d - Natural - all set to zero - w/flash WB also set to zero
Lens: FA 50mm 1.4 - Manual Focus
Lighting: 2 strobes @ 45 degree angles shot through umbrellas w/ manual equal power
Exposure: Manual 1/15 @ 5.0 (2 sec delay - mirror lockup - cable switch)
Chart: Kodak Q-13

First here are the results:




It's interesting to note that in the stepchart analysis chart the lower end stays the same while there is about a 2-3% gain toward the upper end in the DR-On chart. The density response chart also backs this up. Note that the actual noise values (the diamonds) in both noise charts are about the same, i.e. crappy in the extreme dark areas. Not as bad as some people made it out to be, even in the camera manual. Also in the stepchart analysis you can see the pronounced difference of a more rounded shoulder in the lighter areas of the DR-On chart. Before I go on, I would like to say that the D-Range image straight out of the camera appeared slightly darker in the white areas while taking multiple shots and keeping constant lighting conditions. This was illustrated in both charts.

Now on to real world conditions. For sh*ts and grins I wanted to see what would happeded if I took the test images and adjusted the levels - just for black and white points... that's all - nothing else. I then retested and here's what happened:





It seems that after the images were adjusted, the highlights were retained in the DR-On image while they disappeared in the standard shot. This ends up being about a 9-10% gain in the upper dynamic range! Still, the noise levels remained to be the same in both shots - even in the lower levels. Also the histograms showed some moderate banding in both shots.

I'm not sure exactly what the camera is doing internally, but have decided that it is in my best interest to leave the D-Range on while I shoot in Jpeg (of course RAW is best, but I don't need it all the time). The fear of lower light noise is unwarranted and the extra gain in the upper end is nice to have. This is my kindling to throw into the fire and I'm sure there are a few people waiting with cans of gas. I hope this helps some of you and inspires some knit-pickers.

-Brian

11-21-2008, 02:40 PM   #2
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Thanks

After purchase of my K20D on March 5th I started to field-test it against my K10D and on major points of interest was of course D-range :-) Despite of all warnings about increased shadow noise etc. I personally use it almost 100% when outdoors or in contrasty situation- and very happy with it. When doing ETTR I guess it has saved a hundreds of shots for me regarding extra headroom- but nothing scientific, just printed/viewed images...
Once again thanks for heads up and happy shooting, JR
11-21-2008, 02:50 PM   #3
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imaging-resource.com info

maybe something interesting here about K20D dynamic range (at least how much Bright mode kills DR):
Canon EOS 50D Digital Camera Imatest - Full Review - The Imaging Resource!
And my wild guess is that imaging-resource is still making a review of K20D (or at least use it's data in newer reviews (Nikon D90 review did not mention K20D AFAIK and it was slightly older))
Best and happy shooting, JR
11-21-2008, 03:41 PM   #4
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Good grief guys, are we still on a photography forum here, thought for a while I strayed onto a "for boffins" only site.

I just wish I were cleverer to understand any of this, is there a layman translation of this that I should know.

11-21-2008, 05:05 PM   #5
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QuoteQuote:
Good grief guys, are we still on a photography forum here, thought for a while I strayed onto a "for boffins" only site.

I just wish I were cleverer to understand any of this, is there a layman translation of this that I should know.
Ha! It is a little boffinish! ;-p Sorry, I was just looking for a definite answer to what D-Range did. I got tired of reading posts on several forums desputing the color of a red barn and being able to spot an extra 3 lines of wood grain at a 100 yards away. I could never find a real answer so I came up with a test. This was really for me, but thought it would be helpful to others. It does not hurt anything turning it on while shooting in jpeg as long you don't mind shoot at ISO200 or higher. That's what all that mess at the top of the page is saying in a nutshell.

-Brian
11-21-2008, 05:15 PM   #6
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it probably helps a lot in JPEG mode because it brings the extra info back down into the JPEG file...JPEG is 8-bit while RAW is 14-bits (I think).
It'd be more interesting to repeat the test in RAW if you're up to it ;-)
11-21-2008, 05:18 PM   #7
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This may sound silly to the technical experts here but, does D-Range work if shooting RAW or only when shooting JPEG? Thanks!
11-21-2008, 05:50 PM   #8
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While I was searching for an answer, I came across a lengthy post about D-Range working in RAW - it was later shot down. It seems that the camera records whether or not DR is on and the RAW converter handles all the manipulations from there.

Another thing, and this is a little of topic, but the fact that RAW is recorded in 12 or 14 bits and Jpeg in 8 bits is not a legitimate argument. Jpeg records its colors in a logarithmic fashion. It can represent the same amount of colors as RAW can. It's the manipulation/compromising of the image in color, detail retention, and dynamic range that degrades the quality. It does this to save space - although I hear that the highest quality of Jpeg in the K20d is not really much smaller than RAW in the long run. Anyways, enough about numbers - it's Miller time... really.

-Brian

11-21-2008, 09:49 PM   #9
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11-21-2008, 10:19 PM   #10
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I don't know... Maybe I should have just posted a picture of a wagon in the front yard with and without DR with a couple of 100% crops and just say DR was better.

-Brian
11-22-2008, 12:08 AM   #11
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QuoteOriginally posted by the_int21h Quote
While I was searching for an answer, I came across a lengthy post about D-Range working in RAW - it was later shot down. It seems that the camera records whether or not DR is on and the RAW converter handles all the manipulations from there.
<snip>
-Brian
Yes, DR info is recorded in hex location 0x0069 and labelled in EXIF notation as:

Exif.Pentax.DynamicRangeExpansion

It is a Boolean so it can be set to a Value of either On or Off but there are also 4 elements in the array that can be set if the Value is On. There seems to be much more to this than we know.

Jack
11-22-2008, 12:05 PM   #12
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Thanks Brian, I kept up with the 2nd layman version, thanks for that.
11-22-2008, 06:31 PM   #13
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QuoteOriginally posted by jbinpg Quote
Yes, DR info is recorded in hex location 0x0069....
11-23-2008, 02:34 AM   #14
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Good Measurebations and Well Done!

QuoteOriginally posted by the_int21h Quote
I've had a little free time latley and decided to jump into measurbating (oh no!).
-Brian
I am inspired by your spirit of measurbation and actually I must say "well done"! ;-)

However, I can't understand how you can draw up the conclusion that the DR-on is better and preserves more highlights. From looking at your recorded step chart (for the highlight "greys") and the level values, I do not discover any burn or clipping of highlights in both but the DR-off one is just having high levels and thus the overall image will be more contrasty.

Do I missing something? Please enlighten me! :-)

Keep your measurebations up anyway!!
11-23-2008, 07:28 AM   #15
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Thanks for the compliment. I was counting the left most five blocks as the highlights. The cross between the green and blue lines is a higher value than the one with the DR off. I came to my conclusion because there is potential for less banding in these regions and more detail retention. The s-curve is still preserved in this region and hence more "pleasing" to the eye and more film-like. The only drawback is in the mid-range values which can experience a little more banding than with the DR off, but it is not much considering the overall range of these values. This could also explain why people cannot adjust the midtone contrast as much with a DR on. I think Pentax did a fine job with D-Range and it would be in people's better interest to leave it on.

-Brian
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