If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#11
|
|||
|
|||
Interesting comparison (300D/40D)
"Wolfgang Weisselberg" wrote: David J. Littleboy wrote: "frederick" wrote in message Charles wrote: http://www.diwa-labs.com/photoalbum/...=org&id=191587 http://www.diwa-labs.com/photoalbum/...=org&id=191662 To me, it means that the twit who did the test doesn't have a clue as to what dynamic range means (which is ((max signal)/(noise floor)), or the log thereof) or how to test it. To me, it means it's a case of "meaningless", since the test is not described well enough for others to repeat it. IOW: completely worthless. Presumably, the folks at DIWA blithely plugged their images into DxO and took what it gave them. So I take it that there's an implicit: follow the directions that come with DxO and you'll get the same results. Thus I don't think they are guilty of unrepeatability. I'd bet that if you bought DxO and played that game with your camera, you'd get similar results. Simple reality check: Dynamic range must fall by one stop each time the ISO doubles. Must it? Really? Please don't snip the important parts. I was quite careful to say: While this often doesn't hold at low ISOs (due to read noise and circuit noise), it holds at higher ISOs. And this test doesn't show it. But, yes. It has to hold. Pretty much by definition. Is there no possibility that, say, a converter with finite bits of precision, limits the dynamic range? Yes. That's what happens at low ISOs. (See figure 5 in the reference below for the Canon 1DII and 1DIII.) Or from RAW to JPEG (in camera?) or whatever? Testing with jpeg is meaningless. Is there no possibility of the definition of "noise floor" to be ... wrong, Exactly! More likely, they don't even think to define it. I mean, different, in that 'test' due to noise smoothing? (If you talk about every day performance, noise supression does play a role!) Noise reduction entails a loss of resolution. It's equivalent to pixel binning. So reducing your resolution by a factor of two (1.414x linearly) should get you one stop of improved DR. So quoting noise reduced DR values at higher ISOs is seriously stupid. The 40D seems to deliver ~9 stops between ISO 100 and 1600: http://www.dpreview.com/reviews/canoneos40d/page20.asp (which obviously talks about JPEG, since RAW is discussed below). For the camera to deliver the same "DR" from 100 to 1600, means that they are changing the definition of the acceptable low end (the noise floor) at each ISO. That's seriously silly. It's pretty clear that what these tests are actually measuring is the parameters of the default jpeg conversion. Again, see figure 5 in the usual reference. http://www.clarkvision.com/imagedeta...ary/index.html What I see from Charles' curves is that whatever the limitation may be, it is probably not the sensor. (But then a camera _is_ more than the sensor.) This last bit is, of course, important. And part of the camera is the raw converter; being able to actually get the dynamic range captured in the raw file into an RGB image file in a manner that's useful is hard and dependent on the raw converter. David J. Littleboy Tokyo, Japan |
#12
|
|||
|
|||
Interesting comparison (300D/40D)
David J. Littleboy wrote:
"frederick" wrote in message Charles wrote: http://www.diwa-labs.com/photoalbum/...=org&id=191587 http://www.diwa-labs.com/photoalbum/...=org&id=191662 So what does this mean to you? To me, it means that the twit who did the test doesn't have a clue as to what dynamic range means (which is ((max signal)/(noise floor)), or the log thereof) or how to test it. Simple reality check: Dynamic range must fall by one stop each time the ISO doubles. While this often doesn't hold at low ISOs (due to read noise and circuit noise), it holds at higher ISOs. Why? And this test doesn't show it. Or you're mistaken. As a rule, I don't support such unsupported claims as yours. Especially when they have an obvious bias. -- Ray Fischer |
#13
|
|||
|
|||
Interesting comparison (300D/40D)
David J. Littleboy wrote:
"Wolfgang Weisselberg" wrote: http://www.diwa-labs.com/photoalbum/...=org&id=191587 http://www.diwa-labs.com/photoalbum/...=org&id=191662 Presumably, the folks at DIWA blithely plugged their images JPEGs, I guess ... :- Or from RAW to JPEG (in camera?) or whatever? Testing with jpeg is meaningless. If you (want to) use out-of-camera JPEGs, then testing them is anything but. If you only want to display the images on a TV (seriously stupid, I know), you'd best test that setup --- but never try to generalize from it. noise smoothing? (If you talk about every day performance, noise supression does play a role!) Noise reduction entails a loss of resolution. However, not all resolution gives detail. But which does and which does not? That's what a noise reducer has to guess. It's equivalent to pixel binning. Pixel binning can happen before digitisation (and quantisation), thus incurring the read noise only once --- which noise reduction working on the digitized image data cannot. Noise reduction can act differently on local spatial frequencies (and a lot of other things) which pixel binning cannot. I content that noise reduction and pixel binning are somewhat similar, but not equivalent. The 40D seems to deliver ~9 stops between ISO 100 and 1600: http://www.dpreview.com/reviews/canoneos40d/page20.asp (which obviously talks about JPEG, since RAW is discussed below). For the camera to deliver the same "DR" from 100 to 1600, means that they are changing the definition of the acceptable low end (the noise floor) at each ISO. That's seriously silly. It's pretty clear that what these tests are actually measuring is the parameters of the default jpeg conversion. Yep. Which is useful to know for customers who want to do (mosty/only) that. Again, see figure 5 in the usual reference. http://www.clarkvision.com/imagedeta...ary/index.html Yep --- after ISO 1000+ the halving is evident in the 1D. Fancy that, above ISO 1000 even the diva-curves show approximate halfing: 8.5, 7.8, 7.1; 10.1, 9,2 -Wolfgang |
#14
|
|||
|
|||
Interesting comparison (300D/40D)
"Ray Fischer" wrote: David J. Littleboy wrote: "frederick" wrote in message Charles wrote: http://www.diwa-labs.com/photoalbum/...=org&id=191587 http://www.diwa-labs.com/photoalbum/...=org&id=191662 So what does this mean to you? To me, it means that the twit who did the test doesn't have a clue as to what dynamic range means (which is ((max signal)/(noise floor)), or the log thereof) or how to test it. Simple reality check: Dynamic range must fall by one stop each time the ISO doubles. While this often doesn't hold at low ISOs (due to read noise and circuit noise), it holds at higher ISOs. Why? Because of the definitions of "dynamic range" and "stop" and "ISO". And this test doesn't show it. Or you're mistaken. As a rule, I don't support such unsupported claims as yours. Especially when they have an obvious bias. Yes. I'm biased towards technically correct definitions, since anything that isn't technically correct is BS... David J. Littleboy Tokyo, Japan |
#15
|
|||
|
|||
Interesting comparison (300D/40D)
"Wolfgang Weisselberg" wrote:
David J. Littleboy wrote: "Wolfgang Weisselberg" wrote: http://www.diwa-labs.com/photoalbum/...=org&id=191587 http://www.diwa-labs.com/photoalbum/...=org&id=191662 Presumably, the folks at DIWA blithely plugged their images JPEGs, I guess ... :- Or from RAW to JPEG (in camera?) or whatever? Testing with jpeg is meaningless. If you (want to) use out-of-camera JPEGs, then testing them is anything but. But if you are interested in (more) dynamic range, then you won't be shooting jpeg. Jpeg has to throw away at least two stops of dynamic range (at ISO 100) to produce an image with enough contrast to be at all attractive. noise smoothing? (If you talk about every day performance, noise supression does play a role!) Noise reduction entails a loss of resolution. However, not all resolution gives detail. I don't see what you are getting at??? But which does and which does not? That's what a noise reducer has to guess. It's equivalent to pixel binning. Pixel binning can happen before digitisation (and quantisation), thus incurring the read noise only once --- which noise reduction working on the digitized image data cannot. Noise reduction can act differently on local spatial frequencies (and a lot of other things) which pixel binning cannot. Oh. Now I see. You're saying that noise reduction will be applied intelligently so that places without detail will get smoothed, and places with detail won't get mucked with as much. Maybe. But the pre-noise reduction signal has a certain DR, and claiming that you get something for nothing with "intelligent NR" strikes me as suspicious in the extreme. Anyway, "DR" is a property of individual pixels, and claiming that it's changed by certain post-processing is odd. If noise reduction on an image produced with "8-stop DR pixels" produces a "10-stop DR total image", why doesn't applying the same processing to "10-stop DR pixels" produce a "12-stop DR total image". I content that noise reduction and pixel binning are somewhat similar, but not equivalent. That could be. But the bottom line is that a technical parameter like DR should be measured on an un-postprocessed signal, since presumably the "intelligent NR" will do different things to different images. The 40D seems to deliver ~9 stops between ISO 100 and 1600: http://www.dpreview.com/reviews/canoneos40d/page20.asp (which obviously talks about JPEG, since RAW is discussed below). For the camera to deliver the same "DR" from 100 to 1600, means that they are changing the definition of the acceptable low end (the noise floor) at each ISO. That's seriously silly. It's pretty clear that what these tests are actually measuring is the parameters of the default jpeg conversion. Yep. Which is useful to know for customers who want to do (mosty/only) that. Again, see figure 5 in the usual reference. http://www.clarkvision.com/imagedeta...ary/index.html Yep --- after ISO 1000+ the halving is evident in the 1D. The halving starts at ISO 400; the 800 DR is essentially a whole stop below ISO 400. The other cameras are straight lines throughout the range. And both the 40D and D300 are smaller-pixel cameras. Fancy that, above ISO 1000 even the diva-curves show approximate halfing: 8.5, 7.8, 7.1; 10.1, 9,2 Oops. You're right: there is the expected falloff at the far end of these graphs. Still, they have the D300 being pretty flat out to 1600 which is definitely Journal of Irreproducible Results territory, as is claiming 10 stops of DR for the 40D at ISO 1600. Again, these aren't the fat-pixel D3/5D/1DII cameras, they're D200 and smaller pixels. David J. Littleboy Tokyo, Japan |
#16
|
|||
|
|||
Interesting comparison (300D/40D)
David J. Littleboy wrote:
Anyway, "DR" is a property of individual pixels, ... ... DR should be measured on an un-postprocessed signal So is DR a property of a single pixel (presumably within the sensor, or the signal from that sensor) or of the signal from, presumably, multiple pixels? I can imagine a definition that refers to either the capability of the device, or of the device as it may be reduced by following processing, or of an actual signal obtained via that route on some specific occasion. Which would surely be in order of decreasing DR since an instance cannot exceed a capability. Which you mean doesn't matter to me but you seem to be sure what you mean and I am not... Oh, yes, and is DR referred back to light intensity? Mike. -- If reply address = connectfee, add an r because it is free not fee. |
#17
|
|||
|
|||
Interesting comparison (300D/40D)
David J. Littleboy wrote:
"Wolfgang Weisselberg" wrote: David J. Littleboy wrote: "Wolfgang Weisselberg" wrote: Testing with jpeg is meaningless. If you (want to) use out-of-camera JPEGs, then testing them is anything but. But if you are interested in (more) dynamic range, Most people aren't. Most people use P&S cameras and many of those wouldn't know exposure from aperture if it bit them in the nose. :-) And enough people are perfectly fine with out-of-camera JPEGs. Noise reduction entails a loss of resolution. However, not all resolution gives detail. I don't see what you are getting at??? How much resolution do you need for a nicely blurred, out of focus, background? When do you stop getting more detail from more resolution? Could you trade that extra resolution for less noise without harming the image? Oh. Now I see. You're saying that noise reduction will be applied intelligently so that places without detail will get smoothed, and places with detail won't get mucked with as much. That's the idea, AKA "the easy part". Maybe. But the pre-noise reduction signal has a certain DR, and claiming that you get something for nothing with "intelligent NR" strikes me as suspicious in the extreme. You don't get "something for nothing". You trade resolution you (hopefully) don't need for less noise, thus lowering the noise floor (at least in low detail areas, like ... evenly lit gray or black parts designed to measure noise). Anyway, "DR" is a property of individual pixels, While I am quite sure no 'regular' camera does this today, I can imagine one that, guided by it's high resolution matrix metering, - applies analog gain differently per matrix area, and/or - uses an electronic shutter and different exposure times per matrix area. This would increase overall DR, unless you have the brightest and darkest parts too close for the metering to differenciate. Yet the per-pixel-DR would be untouched. and claiming that it's changed by certain post-processing is odd. If noise reduction on an image produced with "8-stop DR pixels" produces a "10-stop DR total image", why doesn't applying the same processing to "10-stop DR pixels" produce a "12-stop DR total image". Assuming "intelligent NR" behaves easily predictable and/or linearly is assuming a naive "intelligent" NR. However, good NR can try to reduce the relevant[1] noise floor. -Wolfgang [1] relevant in the same sense that lossy image compressions like JPEG remove irrelevant visual data and lossy audio compressions (e.g. Ogg Vorbis) tries to keep only the relevant data. |
#18
|
|||
|
|||
Interesting comparison (300D/40D)
David J. Littleboy wrote:
"Ray Fischer" wrote: David J. Littleboy wrote: "frederick" wrote in message Charles wrote: http://www.diwa-labs.com/photoalbum/...=org&id=191587 http://www.diwa-labs.com/photoalbum/...=org&id=191662 So what does this mean to you? To me, it means that the twit who did the test doesn't have a clue as to what dynamic range means (which is ((max signal)/(noise floor)), or the log thereof) or how to test it. Simple reality check: Dynamic range must fall by one stop each time the ISO doubles. While this often doesn't hold at low ISOs (due to read noise and circuit noise), it holds at higher ISOs. Why? Because of the definitions of "dynamic range" and "stop" and "ISO". Spare me the bull****. If you don't know then just say so. And this test doesn't show it. Or you're mistaken. As a rule, I don't support such unsupported claims as yours. Especially when they have an obvious bias. Yes. I'm biased towards technically correct definitions, You're biased towards bull****. -- Ray Fischer |
#19
|
|||
|
|||
Interesting comparison (300D/40D)
David J. Littleboy wrote:
Ray Fischer wrote: David J. Littleboy wrote: Simple reality check: Dynamic range must fall by one stop each time the ISO doubles. While this often doesn't hold at low ISOs (due to read noise and circuit noise), it holds at higher ISOs. Why? Because of the definitions of "dynamic range" and "stop" and "ISO". It would help me a lot to understand what you mean if those definitions were stated here. Please. |
#20
|
|||
|
|||
Interesting comparison (300D/40D)
"Wilba" wrote: David J. Littleboy wrote: Ray Fischer wrote: David J. Littleboy wrote: Simple reality check: Dynamic range must fall by one stop each time the ISO doubles. While this often doesn't hold at low ISOs (due to read noise and circuit noise), it holds at higher ISOs. Why? Because of the definitions of "dynamic range" and "stop" and "ISO". It would help me a lot to understand what you mean if those definitions were stated here. Please. For our purposes, dynamic range is log2((max signal)/(noise floor)). There are a lot of definitions of dynamic range depending on the purpose at hand, but they all are the ratio of the (max signal) to the (noise floor) expressed in a manner that's useful to the problem at hand. In engineering, the concept is well understood. A quick google came up with these and lots more. http://www.its.bldrdoc.gov/fs-1037/dir-013/_1853.htm http://whatis.techtarget.com/definit...13623,00.html# But when photography appears, people get confused. Here's a page full of links to various levels of confusion. http://en.mimi.hu/photography/dynamic_range.html David J. Littleboy Tokyo, Japan |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
OT but Interesting Never the less. | Greg \Blank\ - Lizard King. | In The Darkroom | 0 | March 10th 06 05:56 AM |
EOS 300D & EOS 300D Rebel | fatboybrando | Digital Photography | 4 | March 26th 05 11:55 AM |
EOS 300D & EOS 300D Rebel | fatboybrando | Digital Photography | 0 | March 26th 05 11:47 AM |
Interesting Comparison of Companies. | Mark B. | Digital Photography | 5 | July 13th 04 07:28 PM |