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Author Topic: Ten Years after….  (Read 6594 times)
BernardLanguillier
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« Reply #80 on: February 19, 2014, 07:33:36 AM »
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Amplifying a bit less, but still enough that the noise introduced by the ADC is insignificant compared to the noise in the analog signal coming from the sensor, is an unequivocally good thing for image qualify (less risk of highlight clipping with no significant decrease in SNR), so it puzzles me why so many people wish to characterize as a defect or deception or falsificTionof the ISO speed with inaccurate talk about "underexposure".  And let us be frank: the prefix "under-” is clearly pejorative, implying an error, which is not the case.

I agree with your characterization that this gives the appearance of more "highlight DR", and your inference that this is rather mythical entity, but if the practical consequence is that standard light metering is less likely to lead to highlight problems and with no downside, I do not underatand your cynical attitude to this approach. Can you point to any disadvantage that I am overlooking?

As far as I am concerned I think that what Phaseone does makes a lot of sense because most photographers are a lot more uncomfortable with blown highlights than they are with slightly noisier shadows.

As a result, I don't see "under exposure" at capture or through amplification as a negative thing, but I still think that it is reasonnable to call the approach under exposure relative to a supposed ideal ETTR exposure.

Cheers,
Bernard
« Last Edit: February 19, 2014, 08:01:31 AM by BernardLanguillier » Logged

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Theodoros
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« Reply #81 on: February 19, 2014, 08:50:15 AM »
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OK… Let's go back to the (now old) 22Mp backs then… Their DR is superb because one can "dig" deep into the shadows with less noise, their mid tones linear part is more contrasty right out of the box, they are easier with older lenses, they present no pixelation if blown up to 200%… which means that the image can be up-sampled and can be printed really large, they have enough detail to compete with a 36mp DSLR, if one has an MS version he can shoot the best still image by far, Their 100 Iso is best exposed with EV value as if it was (more or less)  200 Iso of DSLRs, they keep the WA character of WA-MF lenses,  and they are great (if not the optimum) to use with LF cameras as well as to bring life to older LF equipment… The Drawbacks now…, is mainly some (rare-but they are more prone to it than the next resolution step up) moire, which can be treated to much extend with modern software and (for pixel peepers only since these things are very sharp) a bit less resolution…
Did I miss something….? Oh yes!  Shockedthe price that someone can get one and have a perfectly capable back to experience MF and LF!  Wink
« Last Edit: February 19, 2014, 09:15:42 AM by T.Dascalos » Logged
BJL
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« Reply #82 on: February 19, 2014, 10:10:54 AM »
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As far as I am concerned I think that what Phaseone does makes a lot of sense because most photographers are a lot more uncomfortable with blown highlights than they are with slightly noisier shadows.

As a result, I don't see "under exposure" at capture or through amplification as a negative thing, but I still think that it is reasonnable to call the approach under exposure relative to a supposed ideal ETTR exposure.

Cheers,
Bernard
I agree that there is noting wrong with the approach but let me try to get this across one more time:
there is no difference in the exposure received by the sensor, so describing it as under-exposure is flatly wrong, and misleading.
Thus there is no deviation from "supposed ideal ETTR exposure."
The differences are just in the subsequent positioning of the numeric raw levels, so are essentially just different ways of using discrete numerical levels to encode the signal from the sensor.

Just for fun, let me add to the complication by noting that the effect of the difference between 16-bit and 14-bit ADCs is far more important to the anachronistic(*) part of the ETTR ideal about maximizing numerical raw levels.
That difference in bit-depth means that MF backs's lower raw level placements relative to maximum level (which is what DXO measures) still often correspond to the same or higher actual numerical levels. For example:
- if a camera with 14-bit raw output places mid-tones three stops below maximum level (the bare minimum tolerated by the ISO 122323 standard, misinterpreted by some as the one and only correct placement) the raw level is 2^14/2^3 = 2^11, about 2000.
- if a camera with 16-bit raw output places mid-tones four stops below maximum level (halving its "DXO" rating) the raw level is 2^16/2^4 = 2^12, about 4000.
Thus the latter has twice the density of raw levels: twice as many raw levels corresponding to any given range of sensor signal levels, and so is "twice as good" according to the part of the original ETTR idea about maximizing the fineness of raw levels.

So which camera is falling further short of that ETTR ideal?!


(*) Anachronistic because the part of the original ETTR idea about striving to have as many raw levels as possible was relevant when 10-bit and 12-bit ADC themselves imposed a potential limit on the accuracy at which sensor output is recorded, but is largely irrelevant when a modern 14-bit or 16-bit ADC has a wider "dynamic range" (counted for example in bit depth) than the sensor signal (counted for example in f-stops from the brightest photosite's signal down to the noise floor.)
« Last Edit: February 19, 2014, 10:14:43 AM by BJL » Logged
Gandalf
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« Reply #83 on: February 19, 2014, 02:13:32 PM »
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Hi,

Some observations, contradicting yours a little bit. Obviously I have a limited experience shooting only Sony and P45+.

Washed out highlights come from overexposure. If you expose correctly the highlights will be OK. Digital backs underexpose 1-1.5 stops, protecting highlights.

If you use "filme curve" in C1 it will push exposure 1-1.5 stops. Try checking with linear curve to see what the raw image really looks like.

Regarding colour accuracy, I measured colour accuracy on my Sony Alpha 99 and my P45+ and the Sony was much more accurate than the P45, and I have made similar measurements with similar results from published tests on Hasselblad compared to Nikon D800. The colours may be better but more accurate they are not.

I suppose everyone's experience is different, and as you pointed out, it is very important to be specific about what cameras and backs we are comparing. Perhaps my architecture test says more about the Canon than the Leaf. I will say that when I shot my Sony A900 with adapted Leica lenses against an Aptus 8/DF/80mm, while I enjoyed shooting with the Aptus/DF more, the files were extremely similar to my eye. That said, it was sunset and the light was fading quickly, and exposure times were bumping up against the capability of the Aptus back.

I would expect the colors from a Sony A99 to be more accurate than a P45+, particularly in the green/yellow spectrum. Not sure about reds. That said, I stand by my post.
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ErikKaffehr
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« Reply #84 on: February 19, 2014, 02:21:55 PM »
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Hi,

The green/yellow part was most problematic for me, I created DCP profiles that I am quite happy with.

White balance is a major factor. I may think it is a bit warmer with C1 / P45+ than with LR5 and SLT99.

Best regards
Erik

I would expect the colors from a Sony A99 to be more accurate than a P45+, particularly in the green/yellow spectrum. Not sure about reds. That said, I stand by my post.
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Theodoros
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« Reply #85 on: February 19, 2014, 02:42:50 PM »
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I thought this is a conversation for the position (and usefulness) of older 22mp "fat pixel" (9μm) backs… "ten years after" they where introduced (as being the "high end" of the days) and their position in todays market. 
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BJL
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« Reply #86 on: February 19, 2014, 04:14:04 PM »
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My apologies for the tangent in the conversation; back you your original topic:
OK… Let's go back to the (now old) 22Mp backs then… Their DR is superb because one can "dig" deep into the shadows with less noise ...
I have seen no visual evidence of this claim that those older (and noisier) 22MP CCD sensors give better shadows or less noise than modern high resolution CCDs (let alone the coming wave of medium format CMOS sensors) in any relevant comparison of "end products", meaning viewing prints or on-screen images from various cameras at the same size. Because printing (or otherwise displaying) an image with more pixels at the same size and thus at higher PPI increases the SNR of the signal received by the viewers' eyes and improves the fineness of perceived tonal range, cleanness of shadows and such; this is due to "dithering", roughly speaking. This benefit of "more pixel per image" has to be offset against the engineer's measure of the DR of the individual pixels.

A familiar illustration is seen in comparisons between prints of the same size made using the same film emulsion in different formats: the emulsion in each case has the same "DR", but the larger prints with a lower degree of enlargement show improved tonality and cleaner shadows.

P. S. Traditional silver halide negatives have a "per pixel DR" of about 1: if you look close enough, the pixels are all either pure black (silver from an exposed silver halide crystal) or white. All tonal gradations seen are due to "dithering" of that information, due to the size scale of the "pixels" being far below what the eye can resolve.
« Last Edit: February 19, 2014, 04:45:30 PM by BJL » Logged
Theodoros
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« Reply #87 on: February 19, 2014, 05:10:45 PM »
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My apologies for the tangent in the conversation; back you your original topic:I have seen no visual evidence of this claim that those older (and noisier) 22MP CCD sensors give better shadows or less noise than modern high resolution CCDs (let alone the coming wave of medium format CMOS sensors) in any relevant comparison of "end products", meaning viewing prints or on-screen images from various cameras at the same size. Because printing (or otherwise displaying) an image with more pixels at the same size and thus at higher PPI increases the SNR of the signal received by the viewers' eyes and improves the fineness of perceived tonal range, cleanness of shadows and such; this is due to "dithering", roughly speaking. This benefit of "more pixel per image" has to be offset against the engineer's measure of the DR of the individual pixels.

A familiar illustration is seen in comparisons between prints of the same size made using the same film emulsion in different formats: the emulsion in each case has the same "DR", but the larger prints with a lower degree of enlargement show improved tonality and cleaner shadows.

P. S. Traditional silver halide negatives have a "per pixel DR" of about 1: if you look close enough, the pixels are all either pure black (silver from an exposed silver halide crystal) or white. All tonal gradations seen are due to "dithering" of that information, due to the size scale of the "pixels" being far below what the eye can resolve.
A usual mistake we do, is to compare "memories" we have with modern equipment… The older backs have improved a lot from modern software… actually all backs have improved - but the older the back, the more evident the improvement. Please check this for DR… there was no other reason I shot it, but to test imacon 528c for DR in single shot.
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BernardLanguillier
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« Reply #88 on: February 19, 2014, 06:24:03 PM »
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I agree that there is noting wrong with the approach but let me try to get this across one more time:
there is no difference in the exposure received by the sensor, so describing it as under-exposure is flatly wrong, and misleading.
Thus there is no deviation from "supposed ideal ETTR exposure."
The differences are just in the subsequent positioning of the numeric raw levels, so are essentially just different ways of using discrete numerical levels to encode the signal from the sensor.

Let's compare two situations, leaving DSLRs aside:
1. Camera A where an exposure of 1/60 sec at f8 and ISO 100 results in highlights using the highest possible values in the raw file, just short of clipping, the so called ETTR. Let's assume, by chance, that the level of illumination used in this test is the one defined by the ISO standard,
2. Camera B, say an IQ280, with the exact same exposure results in the raw values being 2 stops short of the brightest possible values in the raw file.

I could be wrong, but according to my understanding of the definition of ISO in digital defined in ISO Standard 12232, sensor sensitivity, rated by its ISO number, is related to the exposure necessary to saturate the camera. Which means to reach the highest possible raw values.

According to this definition, the actual digital ISO of Camera B is lower than 100 when ISO100 is dialed in camera.

For all practical matters, this is similar to what film companies used to do when they rated Velvia at 50 while it was actually an ISO40 film. The purpose was to expose the film less than the camera thought in order to avoid blowing highlights and saturating colors more, in other words under-expose the film.

I fail to see how the approach used by Phaseone is not about under-exposing the sensor per the ISO definition of what ISO rating is.

Now, I believe that the approach used with camera B:
1. Results in more ability to brighten highlights in post processing without running into clipping, which is seen by most photographers as a great thing,
2. Results in shadows having less raw values available per shadow stop, which is not that great for advanced users who would probably want to tap better in the DR potential of their camera, but is still not a disaster.

Now, what part are you not in agreement with?  Smiley

Cheers,
Bernard
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BJL
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« Reply #89 on: February 19, 2014, 09:38:44 PM »
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Bernard,
There are so many errors in your post, and we are so far off the topic of his thread that I propose to respond by starting another thread on the whole subject of misunderstanding of the multiple ISO 12232 defined measures of (1) exposure index, (2) recommended MINMUM usable exposure index based on highlight handling and (3) recommended MAXIMUM exposure index based on shadow handling ... Along with your persistent failure to see he difference between how much exposure the SENSOR gets and how much that signal I s subsequently AMPLIFIED in order to produce the raw levels. Meanwhile, I suggest reading a bit about ISO 12232: there is a decent Wikipedia page.
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Theodoros
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« Reply #90 on: February 20, 2014, 02:03:37 AM »
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If I may, isn't exposure required to just protect HLs from blowing different for different developers? …and isn't it different from past developers to the modern versions of them? Another thing… isn't exposure relevant to the lens flare resistance? I mean a prone to flare lens limits mid tone contrast, while a flare resistant lens improves it… obviously the later is easier to expose for HLs, since the first one will lead to a dull/unprintable image… Now coming back to the subject… aren't "fat pixel" backs better with lenses when wide open? And… (especially with the Kodak sensor) don't the "fat pixel" backs have more contrasty (and linear) mid tones in their raw (which is exactly what some people call the "fat pixel magic")?
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BernardLanguillier
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« Reply #91 on: February 20, 2014, 02:06:03 AM »
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Bernard,
There are so many errors in your post, and we are so far off the topic of his thread that I propose to respond by starting another thread on the whole subject of misunderstanding of the multiple ISO 12232 defined measures of (1) exposure index, (2) recommended MINMUM usable exposure index based on highlight handling and (3) recommended MAXIMUM exposure index based on shadow handling ... Along with your persistent failure to see he difference between how much exposure the SENSOR gets and how much that signal I s subsequently AMPLIFIED in order to produce the raw levels. Meanwhile, I suggest reading a bit about ISO 12232: there is a decent Wikipedia page.

Sure, no problem.

Cheers,
Bernard
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eronald
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« Reply #92 on: February 20, 2014, 07:06:52 AM »
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Now why again are you all beating this horse cadaver?

Edmund
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Theodoros
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« Reply #93 on: February 20, 2014, 10:15:21 AM »
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Well… not many systems could achieve this price on e-bay…..

http://www.ebay.co.uk/itm/Contax-645-kit-with-PhaseOne-P25-digital-bag-/271401131897?_trksid=p2047675.l2557&autorefresh=true&ssPageName=STRK%3AMEWAX%3AIT&nma=true&si=SShfe1KP%252BxxWtwkYHZGmve51%252BYs%253D&orig_cvip=true&rt=nc
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BJL
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« Reply #94 on: February 20, 2014, 12:10:53 PM »
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Sure, no problem.

Cheers,
Bernard

Here is it: mostly some facts on what the two most relevant standards organizations (the International Organization for Standardization [ISO] and the Camera and Imaging Products Association [CIPA]) say about measuring and reporting on exposure index, sensitivity etc.: http://www.luminous-landscape.com/forum/index.php?topic=87439.msg711760#msg711760

Not that this is very likely to change opinions on how MFD backs should operate, but at least I hope to stop people making flatly false claims about what ISO says, what the "ISO speed" of a camera means, and so on.
« Last Edit: February 20, 2014, 12:14:22 PM by BJL » Logged
Theodoros
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« Reply #95 on: February 20, 2014, 12:49:40 PM »
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Here is it: mostly some facts on what the two most relevant standards organizations (the International Organization for Standardization [ISO] and the Camera and Imaging Products Association [CIPA]) say about measuring and reporting on exposure index, sensitivity etc.: http://www.luminous-landscape.com/forum/index.php?topic=87439.msg711760#msg711760

Not that this is very likely to change opinions on how MFD backs should operate, but at least I hope to stop people making flatly false claims about what ISO says, what the "ISO speed" of a camera means, and so on.
You are right of course on what the setting for ISO should be… but, (why there is always a but in engineering?  Huh) with digital, things get a bit more complicated… a sensor receives light on all its surface and that includes corners... Grin (you see where I'm getting at… but its more  Wink), then there is the fact that people use different focal lengths…. and then… (especially) the older backs are designed to be used with different cameras and different batch of lenses with each one of them… Now these different lenses have also different rear (last) element too and quite often it differs in size…. Remember when Sinar increased the noted sensitivity on their E-motion backs by one stop (on 22, 54lv, 75 & 75lv) without altering anything on signal amplification?  Smiley Guess why?  Roll Eyes …. The 22mp backs are among the best in DR if exposed right… and what "right" is, should be found from the owner depending on the scene… If he masters the sensitivity with respect to the situation and the distribution of light across the scene (which he should if he is a photographer), the results can be excellent.
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BJL
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« Reply #96 on: February 20, 2014, 01:09:17 PM »
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You are right of course on what the setting for ISO should be… but, (why there is always a but in engineering?  Huh) with digital, things get a bit more complicated ...
What are you talking about? The standards ISO 12232-2006 and CIPA DC-004 that I mention are all specifically for Digital Still Cameras, so how can digital make things "a bit more complicated"?
And since the topic is exposure index, ISO speed, and ISO speed latitude, your talk about different focal lengths and back designs is irrelevant.

P. S. There is of course at least one argument for still using a 22MP sensor back: cost. It is the least expensive way to get a format as big as 48x36mm, which has some advantages over smaller formats like 44x33mm, like less of the enforced cropping of the image from lenses designed for 645 format.
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Theodoros
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« Reply #97 on: February 20, 2014, 01:44:02 PM »
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What are you talking about? The standards ISO 12232-2006 and CIPA DC-004 that I mention are all specifically for Digital Still Cameras, so how can digital make things "a bit more complicated"?
And since the topic is exposure index, ISO speed, and ISO speed latitude, your talk about different focal lengths and back designs is irrelevant.

P. S. There is of course at least one argument for still using a 22MP sensor back: cost. It is the least expensive way to get a format as big as 48x36mm, which has some advantages over smaller formats like 44x33mm, like less of the enforced cropping of the image from lenses designed for 645 format.
What I'm talking about is that photons are not received evenly across the sensor area (and this is affected by lenses and their design too), while sensitivity is an average on the whole sensor area….
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DavidP
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« Reply #98 on: February 20, 2014, 03:53:29 PM »
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I found Moire to be a huge issue with the P-25 sensor with the type of photography I do. Mostly in clothing, always seemed  to be popping up and could be very difficult to clean up. With the later backs it has become almost a non issue. If you are shooting things with fabric you would be better off with the D800
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Theodoros
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« Reply #99 on: February 20, 2014, 04:07:11 PM »
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I found Moire to be a huge issue with the P-25 sensor with the type of photography I do. Mostly in clothing, always seemed  to be popping up and could be very difficult to clean up. With the later backs it has become almost a non issue. If you are shooting things with fabric you would be better off with the D800
True… fabric structure pro work is where "fat-pixel" backs should be avoided… Well, nothing is perfect in this world.  Cheesy
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