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OM-D E-M5 Photographic Dynamic Range and Read Noise

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Of course, but I wanted to asked the question from the "demanding users'" point of view. ;)

You could also ask, why does it get so much better at ISO 400 and what keeps them from using the same technology for lower ISO?
 
The OMD data follows the "ideal FT" curve as ISO grows. Pretty awesome in technology terms. If Sony follows that for the rest of their sensor line, we may eventually get the ideal FF and APS-C perfomance.

And I thought that sensor tech had leveled off (well, now it seems to be almost there, actually).

Do you have any idea how they did that?
--
Renato.
http://www.flickr.com/photos/rhlpedrosa/
OnExposure member
http://www.onexposure.net/

Good shooting and good luck
(after Ed Murrow)
 
I should have read this before posting below, thanks. Still, it seems that Sony has been working with some high ISO gain technique to improve DR results, abandoning their more usual "linear" approach.
bclaff said:
brunobarolo said:
Please allow a layman's stupid question: The photographic dynamic range E-M5 graph (at least for ISO 800 and above) is very close to the ideal 4/3 graph. Would that mean that the laws of physics don't allow much improvement any more for dynamic range and thus shadow noise at high ISOs in future 4/3 sensors?

Or what does "ideal 4/3" mean?
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Not a stupid question at all.

I don't measure or report based on "real" ISO but on the manufacturer stated ISO.

In this case, if you apply the DxOLabs numbers, the curve is shifted about 1/3EV to the right of where it "should" be. That's why it's so close to the ideal line.

When comparing cameras using my PDR curves, especially across brands, you should probably not take differences of less than 1/2 EV too seriously.
--
Bill (visit me at http://home.comcast.net/~NikonD70/ )
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--
Renato.
http://www.flickr.com/photos/rhlpedrosa/
OnExposure member
http://www.onexposure.net/

Good shooting and good luck
(after Ed Murrow)
 
bclaff said:
Anders W said:
Timur Born wrote:

Perhaps Bill can shed further light on the possible technical reasons for this somewhat strange read-noise curve. Two-stage amplifier or what? But why then this pattern only at the very beginning of the ISO range?
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Some "high end" Canon models use a two-stage amplifier but most manufacturers push/pull the raw data in their firmware. (FWIW, Nikon always uses a single amplifier.)

From http://home.comcast.net/~NikonD70/Charts/RN_e.htm#OM-D%20E-M5_12 it would appear that E-M5 intermediates are pushed; so ISO 250 and ISO 320 are pushed from ISO 200.

Contrast this with a Canon camera http://home.comcast.net/~NikonD70/Charts/RN_e.htm#EOS%207D_14,OM-D%20E-M5_12 where it seems clear that intermediate ISO are either pushed or pulled from the nearest "whole" ISO.

The effect is more pronounced at the low ISOs but is present at all intermediate ISOs. The reason stems from how much of the read noise is at the photosite as opposed to how much is being added by the Analog to Digital Converter (ADC). As the value in electrons levels out the effect is harder to see.
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Thanks for your answer Bill. One question to make sure I understand you right: By pushing/pulling, you mean digital scaling as opposed to analog amplification, right? One reason I am wondering is that the E-M5 doesn't quite behave as it should if the intermediate ISOs of 250 and 320 were just digitally scaled from 200. As your read-noise graphs, as well as my own earlier observations indicate, read noise as measured in electrons does fall a bit as you progress from 200 to 250 and 320, just not nearly as much as in the transition from any of the previous ISOs to 400. See here (penultimate paragraph):

http://forums.dpreview.com/forums/read.asp?forum=1041&message=41988325

What would be your take on this?
 
rhlpetrus said:
Why do the D7000 and OMD curves differ, the former stabilizes at some point while the latter keepd going, as ISO moves up?

Is that an ADC issue?
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My guess would be that the D7000 a) stops analog amplification and b) does not bother to digitally scale the RAW data upwards from ISO 800 on whereas the E-M5 does at least one of the two.
 
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