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Thread: The P45+ and DR. And noise. And...

  1. #151
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    Re: The P45+ and DR. And noise. And...

    what i found interesting was the comment that higher ISO than native simple underexposes and attaches a tag for the processing sw to work with

  2. #152
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    Re: The P45+ and DR. And noise. And...

    Here is a link to a rather mathematical explanation and treatment of sensor noise, DR, etc. I am not claiming to be able to understand all of this, but it is worth reading, even past all the equations, to get some understanding of what is going on when we push the ISO from 100 to 400 or 800. Although the actual tests were done with Canon and Nikon DSLRs in this case, and may not seem appropriate in this thread, the theory is very germane and does apply. The more interesting thing to me is that the shot that Thierry took and posted here seems to completely underscore and support what this guy is talking about.....shoot closer to base ISO and under/overexpose to get the best results with processing.

    http://theory.uchicago.edu/~ejm/pix/...ise/index.html

    LJ

  3. #153
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    Re: The P45+ and DR. And noise. And...

    Quote Originally Posted by jlm View Post
    what i found interesting was the comment that higher ISO than native simple underexposes and attaches a tag for the processing sw to work with
    That is precisely the point that the article I linked to makes. The difference comes in with how the software is able to read those tags, and the suggestion is do not rely on the generalist treatment, but manage that yourself in how you process the images. In other words, shoot closer to base ISO and push/pull things with the adjustments in the various converters. In the case of Brumbaer, I think Stefan has gone to some extra lengths to handle each channel much better, and thus produce what may be an optimal conversion. I just do not see that happening with the more generalist conversions that are trying to handle every RAW file produced. I could be very wrong here, but my gut, and experience keeps telling me to look more closely at that software supplied by the camera makers, as it may have a lot more value for better conversions of their files. Unfortunately, until very recently, most of it has been too obtuse for us to seriously consider in our workflows (DPP comes to mind with Canon files for me). Let's hope that starts to change, or that any "universal" files, such as DNG actually do contain all the information and are done with a top notch conversion from the native files BEFORE they get written as DNG files for use in applications that have better workflow.

    LJ

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    Re: The P45+ and DR. And noise. And...

    Quote Originally Posted by fotografz View Post
    I took the image to 100% (actual pixels) Greg, and cropped a section from that.

    My partner shot back-up with a 1DsMKII and the files were not selected by the art director client, in fact my partner trashed most of them after seeing the MFD shots of the same scenes ... the final file use was for laminated trade show murals at 6 feet wide and up ... therefore the Canon nor the Nikon would and could not NOT produce better end results as you presumed without knowing what they were for.
    Marc,

    Good info regarding the final usage, I was curious to know if the loss of detail from the noise offset the size difference. The D3 would deliver much nicer ISO 800 shots than the 1DsMII but point taken.

    Regarding the crop, it's not a 100% crop of the scene you are showing. I upressed your whole scene to the H3D-31 dimensions of 4872 x 6496 and then took a 100% crop of that and get the following which is a much larger area than your crop shows.

  5. #155
    Senior Member Graham Mitchell's Avatar
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    Re: The P45+ and DR. And noise. And...

    Whether the correct ISO response is created in hardware or software is a moot point, imo. The results are all that matter.

    Either way, when your expose for an ISO 800 image you are capturing 1/8 as many photons as you would if exposing for ISO 100, so the range of possible discrete signal values is smaller. We'll come back to this later.

    Afaik, with hardware gain the small signal taken from the sensor is amplified electrically before the AD (analogue-to-digital) conversion. This may or may not result in more noise. Perhaps someone else can chime in. It certainly risks causing clipping unnecessarily.

    With software conversion the lower-level data from the AD conversion is multiplied so that the range of data values matches the selected sensitivity. The disadvantage of doing it in software is that the low level signal fed to the AD converter will not take advantage of the full bit depth. In other words, if you underexpose by 3 stops, your signal will only be expressed over 13 bits rather than 16.

    However, if there is no meaningful information in the least significant bits (due to the limited number of possible discrete signal values) then the difference becomes academic and insignificant. I suspect that this is the case with MFDBs, and the results seem to support that conjecture. This is why I don't see the point of Panopeeper's analyses, unless of course he is posting merely on behalf of the intellectually curious.

  6. #156
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    Re: The P45+ and DR. And noise. And...

    Quote Originally Posted by jlm View Post
    what i found interesting was the comment that higher ISO than native simple underexposes and attaches a tag for the processing sw to work with
    ISO settings without associated A/D gain are common among DSLRs as well. For example the highest ISO gain of all Canon's is 1600, with the exception of the 1DMkIII (larger pixels sites!); some are even lower. The top ISO of the Nikon D300 is 1600 and of the D3 is 6400 (very large pixel sites). Many other DSLRs don't go over 800.

    Higher ISOs are manufactured numerically in the camera, i.e. the digital values of the highest true gain get multiplied by two or four. This approach is important for JPEG created in-camera, but it reduces the dynamic range by one respecively two stops, so these should not be used when recording raw data. MFDBs are designed for recording raw, thus they don't fake the ISO in the camera, instead the raw processor pushes the intensity. Thus the difference is only formalistic between shooting with ISO 800 and pushing the result by one stop, and shooting with ISO 100 and pushing the result by four stops.

    Note: I don't know if there are other MFDBs beside the Phase One P45+ with true ISO gain.

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    Re: The P45+ and DR. And noise. And...

    Quote Originally Posted by foto-z View Post
    if there is no meaningful information in the least significant bits (due to the limited number of possible discrete signal values) then the difference becomes academic and insignificant. I suspect that this is the case with MFDBs, and the results seem to support that conjecture
    Another way to express this is: the 16bit depth allows to store the total usuful gain, as if always the highest useful ISO were selected, in contrast to DSLRs, which store a "window" of the total gain.

    In light of this, it is questionable if the 16bit depth of the P45+ is reasonable at all.

    This is why I don't see the point of Panopeeper's analyses, unless of course he is posting merely on behalf of the intellectually curious.
    There are masses of DSLR owners, who don't know how to make the most of their camera; they are wasting only a few hunder to a few thousand bucks.

    However, if someone paid a few tens of thousands bucks for a camera and back, then some intellectual curiosity about how to use it the most effectively should not be the exception.

  8. #158
    Sr. Administrator Jack's Avatar
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    Re: The P45+ and DR. And noise. And...

    Quote Originally Posted by thsinar View Post
    I don't have time to drive around and look for a "blue" subject, as suggested by Jack (for the blue channel).
    Thierry, if you are going to quote me, please quote my post directly, not paraphrased as you happen to "remember" it! Here is my actual comment for clarification:

    Frankly, I think smooth green flora isn't the best subject to show noise either. As I indicated earlier in this thread, I think the real test is a McBeth card under controlled lighting so we can see how each color responds to each ISO.
    So yes, if we want a thread on ISO performance, let's do it in a controlled way -- and we can have panopeeper analyze each cameras capture to his hearts content and report back to us.

    In the meantime, I'm more interested in making useful images ,
    Jack
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  9. #159
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    Re: The P45+ and DR. And noise. And...

    Quote Originally Posted by Greg Seitz View Post
    Marc,

    The Cowboy crop that you show is actually only a 50% crop of the overall shot you showed which effectively means it's a crop of your original downsized to 8 megapixels. Do you have the full 100% crop? Also curious in this circumstance if you needed high ISO why not pull out the D3 or 1DMIII since they seem likely to produce better end results in this case even with their lower number of pixels. Just trying to get my head around the capabilities of these backs.

    Thanks,

    Greg
    Greg:

    Doesn't your method only work assuming the original shot was the full frame image resized for the web and not cropped before posting?

    Robert

  10. #160
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    Re: The P45+ and DR. And noise. And...

    Sorry Jack, I was too lazy on this one and to search. All I want to say is that one can as well and even very well check noise behaviour with a green subject.

    Best regards,
    Thierry

    Quote Originally Posted by Jack Flesher View Post
    Thierry, if you are going to quote me, please quote my post directly, not paraphrased as you remember it! Here is my actual comment for clarification:



    So yes, if we want a thread on ISO performance, let's do it in a controlled way -- and we can have panopeeper analyze each cameras capture to his hearts content and report back to us.

    In the meantime, I'm more interested in making useful images ,

  11. #161
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    Re: The P45+ and DR. And noise. And...

    Quote Originally Posted by robsteve View Post
    Greg:

    Doesn't your method only work assuming the original shot was the full frame image resized for the web and not cropped before posting?

    Robert
    Robert,

    That's correct but usually people show the full scene followed by a crop. In the absence of Marc mentioning the first shot was already a crop I have to go by what was presented. I'll mention as well Guy has made the mistake of not posting 100% crops a couple of times when he has posted so it's an easy mistake to make.

    Thanks,

    Greg

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    Re: The P45+ and DR. And noise. And...

    Quote Originally Posted by Greg Seitz View Post
    Marc,

    Good info regarding the final usage, I was curious to know if the loss of detail from the noise offset the size difference. The D3 would deliver much nicer ISO 800 shots than the 1DsMII but point taken.

    Regarding the crop, it's not a 100% crop of the scene you are showing. I upressed your whole scene to the H3D-31 dimensions of 4872 x 6496 and then took a 100% crop of that and get the following which is a much larger area than your crop shows.
    I have a D3, it doesn't cut it compared to the H3D/31 ... I don't use the the D3 for anything other than low light wedding shots printed @ 8X10 ... or commercial stuff that will be printed small ... which is almost nothing these days since clients want to multi-purpose the images from internet use to 8' display prints.

    Your enlargement of my cowbot shot is misleading ... blowing up a cropped j-peg web upload looks horrible ... I understand you are showing what the severe crop is suppose to be, but others may get the wrong impression ... so please allow me to show it:

    Again, the specifics are: H3D/31 @ 1/180th shutter, ISO 800 pushed 1.5 to 2 stops in Phocus, HC 150/3.2 & 1.7X ... any slight lack of clarity at this magnification is due to shooting 255mm @ 1/180th shutter.
    Last edited by fotografz; 23rd July 2008 at 02:29.

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    Re: The P45+ and DR. And noise. And...

    I think it looks damn good given the ISO, shutter and everything else . i would have expected that hat to really blow it with noise and it did not. Well Marc you hit my thoughts when I was just ready to buy a D3 with cash in hand and i decided to go MF. This is exactly the reason BIG
    Photography is all about experimentation and without it you will never learn art.

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  14. #164
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    Re: The P45+ and DR. And noise. And...

    Now that's more like it. Looks really good.

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