Equipment & Techniques > Cameras, Lenses and Shooting gear

Putting DR into perspective..

(1/7) > >>

ErikKaffehr:
Hi,

Lot of (DR) Dynamic Range oriented discussions recently. This posting is intended to put DR in perspective.

My experience is that my cameras mostly had decent DR for my needs. One of my observations was that I very seldom needed to resort to HDR to get good images. I also feel that the need of DR is often overrated.

Let's start looking at this image:


Now, lets look at an area of deep shadow, brightened up in Lightroom:


The disc of the sun can be recovered in Lightroom pretty well:


Below is the raw histogram of the full image, something like 10EV of dynamic range in this image:


This is one of the very dark areas. Check the histogram, the pixels have a nice Gaussian distribution. Full well capacity on this sensor is around 60000 e/pixels and readout noise perhaps 2-3 electron charges. The raw data is 14 bit wide so each digital number corresponds to about 4 photons. The red channel is centered about 20 counts corresponding to about 80 photons. So noise should be SQRT(80) 8.9 photons, say  photons corresponding to +/-2 counts. So the histogram should be something like 2Sigma * 2 wide. Well it looks like a bit wider than that, but we still see very little evidence of readout noise.

I guess that most modern cameras would be able to handle this scene pretty well.

Best regards
Erik

ErikKaffehr:
Hi,

This is another image, with wider dynamic range, first let's look at an HDR exposure (P45+ exposures from 1s to 30s), fused in Lumariver HDR.



The whole luminance range is impressive, perhaps 14 stops


Now, lets look at small detail of the piano:



And also check a small area on the piano cover in RawDigger. The peaks are nice gaussians.


The image below is from a 2.5 s exposure on the Sony Alpha 99:


The histograms on the tiny part of the piano cover still look good, albeit each second channel is empty (due to Sony "lossless" compression?)


Here is the same part of the piano on the P45+, note 1s exposure compared to 2.5s on the SLT99:

The P45+ had about 1 stop less exposure, and here the piano cover got noisy, I guess we can see the effects of readout noise:


Raw images are here:

http://echophoto.dnsalias.net/ekr/Articles/DRArticle/NativeRaws/CF045286.IIQ
http://echophoto.dnsalias.net/ekr/Articles/DRArticle/NativeRaws/20140617_lumariver.dng
http://echophoto.dnsalias.net/ekr/Articles/DRArticle/NativeRaws/_DSC4758.ARW

Just a comment, these images were from a "real world" shooting. The P45+ was exposed at 1s while the SLT99 had a 2.5s exposure. Both exposures were based on camera histogram. The idea is not to demonstrate the difference between the two camera/sensor combination. Lab conditions are fare more appropriate for that kind of comparison.

Also, I have been told that my P45+ is a decent sample.
Best regards
Erik

BernardLanguillier:
Nice building!

Cheers,
Bernard

NancyP:
That's pretty interesting. RAW Digger seems to be a learning tool, I will have to look into it. I suppose a lot of the DR talk is centered around the sorts of images where one can't get a bracket set without some movement, backlit runners or birds, waving grain and deep shadow, etc.

Do you ever get posterization with the Sony lossless compression data?

NancyP:
Consulting Dr. Google, Dr. Google in the house?  ::)

The answer to my posterization question is yes, says the RAW Digger blog:
http://www.rawdigger.com/howtouse/sony-craw-arw2-posterization-detection

Navigation

[0] Message Index

[#] Next page