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Thread: Clearing up confusion with Brumbaer/Sinar backs

  1. #51
    thsinar
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    Re: Clearing up confusion with Brumbaer/Sinar backs

    nothing adding to the debate, but I wish to correct it:

    Graham has used a Sinar eMotion 54 LV for his images:
    the Sinar e22 (eMotion 22) does not exist anymore since a long time. The eMotion 54 LV has a completely different electronic sensor board (among others).

    Best regards,
    Thierry

    Quote Originally Posted by Panopeeper View Post
    ... image of a Sinar e22

  2. #52
    Panopeeper
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    Re: Clearing up confusion with Brumbaer/Sinar backs

    Quote Originally Posted by thsinar View Post
    Graham has used a Sinar eMotion 54 LV for his images:
    the Sinar e22 (eMotion 22) does not exist anymore since a long time
    Graham posted a serie of raw files at the beginning of this thread, with ISO 50, 100, 200 and 400. The metadata of these DNG files, converted by Brumbaer's, contains

    Make: SINAR
    Model: eMotion 22
    Unique camera model: e54 on Rollei 600x

    Make and Model usually come from the camera; the unique camera model comes from the raw converter. However, I do not have the original raw files to confirm this. I though e54 is a sub-classification of eMotion 22.

    The full image size is 4008x5344pix, perhaps this helps in cearing, what was happening.

    Anyway, my statements regarding the ISO were not based on the a priory knowledge of the model but on the actual data in these raw files.

  3. #53
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    Re: Clearing up confusion with Brumbaer/Sinar backs

    Quote Originally Posted by shakeshuck View Post
    Upping the fictional ISO will result in underexposure, which would REDUCE the quality of the tonal range, but is compensated for by the increase in levels provided by upping the gain?
    Maybe I didn't explain myself properly.

    If the scene is underexposed, we reduce the amount of tonal levels that are being recorded around a certain luminance value, therefore we are losing detail. But you are saying that if the gain is hardware gain, those intermediate values are not actually lost, but recorded correctly. Software gain would result in those values being lost.

  4. #54
    Senior Member Graham Mitchell's Avatar
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    Re: Clearing up confusion with Brumbaer/Sinar backs

    Quote Originally Posted by Panopeeper View Post
    Graham posted a serie of raw files at the beginning of this thread, with ISO 50, 100, 200 and 400. The metadata of these DNG files, converted by Brumbaer's, contains

    Make: SINAR
    Model: eMotion 22
    Unique camera model: e54 on Rollei 600x
    I can confirm they were taken with an eMotion 54LV

  5. #55
    Panopeeper
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    Re: Clearing up confusion with Brumbaer/Sinar backs

    Quote Originally Posted by shakeshuck View Post
    If the scene is underexposed, we reduce the amount of tonal levels that are being recorded around a certain luminance value, therefore we are losing detail. But you are saying that if the gain is hardware gain, those intermediate values are not actually lost, but recorded correctly. Software gain would result in those values being lost.
    I have been thinking for a while about a fitting analogy. Here is one; I am not fully happy with it, but I don't have any better. Suggestions are welcome, we will share the royalty fees.

    Let's imagine we have water in a container and we want to measure its volume.

    First we measure it in gallons. If the amount is large, like in a swimming pool, we get a large number and a relatively good measurement. However, if there is much less water there, the resulting number is lower, and the difference between the measurement of two containes with almost identical amount of water is very small to zero. In order to get a more accurate measurement, we measure the leftover (less than a gallon) as well, in quarts. If the amount is even less, we have to measure the leftover after the quart, so we turn to a pint.

    This way we can measure and compare small amounts as well. However, there is a downside: the smaller the unit, the less the accuracy of measurement, some measurements will be off.

    A pixel well captures photons; these turn into measurable electric charge. The higher the exposure, the higher the difference in the charges of two pixels, which were not equally illuminated.

    The closer we "look", the more fine measurement we can take, thus we can distinguish between like charges. At the same time, more and more measurements will be off.

    This off-measurement is one source of noise.

    Now, to the substitution of ISO gain by multiplication: if we measure everything in gallons and multiply the result by eight, then we get that very measurement in pints - but that's not the same, as if we had measured it in pints.
    Last edited by Panopeeper; 24th May 2008 at 17:37.

  6. #56
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    Re: Clearing up confusion with Brumbaer/Sinar backs

    I could use a pint or two after trying to get my head around this stuff

  7. #57
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    Re: Clearing up confusion with Brumbaer/Sinar backs

    Quote Originally Posted by Panopeeper View Post
    I have been thinking for a while about a fitting analogy. Here is one; I am not fully happy with it, but I don't have any better. Suggestions are welcome, we will share the royalty fees.

    Let's imagine we have water in a container and we want to measure its volume.

    First we measure it in gallons. If the amount is large, like in a swimming pool, we get a large number and a relatively good measurement. However, if there is much less water there, the resulting number is lower, and the difference between the measurement of two containes with almost identical amount of water is very small to zero. In order to get a more accurate measurement, we measure the leftover (less than a gallon) as well, in quarts. If the amount is even less, we have to measure the leftover after the quart, so we turn to a pint.

    This way we can measure and compare small amounts as well. However, there is a downside: the smaller the unit, the less the accuracy of measurement, some measurements will be off.

    A pixel well captures photons; these turn into measurable electric charge. The higher the exposure, the higher the difference in the charges of two pixels, which were not equally illuminated.

    The closer we "look", the more fine measurement we can take, thus we can distinguish between like charges. At the same time, more and more measurements will be off.

    This off-measurement is one source of noise.

    Now, to the substitution of ISO gain by multiplication: if we measure everything in gallons and multiply the result by eight, then we get that very measurement in pints - but that's not the same, as if we had measured it in pints.
    The more you explain this, the more little pieces fall into place!

    However, (and please don't think the student is trying to tell the master here), I thought (unless things have changed in the last 6 or 7 years), the measurements for one 'exposure' of an image were the same size across that image's DR, which is why measurement accuracy falls off with underexposure. I can see that using software gain (and measuring in pints) doesn't change anything, but I didn't think gallons and pints were mixed during one exposure. Or are you saying that that is what effectively happens when using hardware gain?

    And how are we, as non-engineers, supposed to know which ISO settings are using hardware or software-based solutions? You said in the case of the Canon it was part one and part the other.

  8. #58
    Panopeeper
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    Re: Clearing up confusion with Brumbaer/Sinar backs

    Quote Originally Posted by shakeshuck View Post
    and please don't think the student is trying to tell the master here
    pleeeze

    I thought (unless things have changed in the last 6 or 7 years), the measurements for one 'exposure' of an image were the same size across that image's DR, which is why measurement accuracy falls off with underexposure
    You are right. Analogies always carry the risk of misleading.

    If you are judging, that the exposure won't be enough (based on metering or your feeling), you decide for the "finer units" and that applies to all pixels.

    how are we, as non-engineers, supposed to know which ISO settings are using hardware or software-based solutions?
    We, non-engineers (and even those of us, who are engineers) are not supposed to know this. You don't find any specification from major camera makers stating this. The maximum is, that the ISO settings past the last real one are characterized as "expansion" or "high" and often they can be blocked from accidental selection; furthermore they are excluded from auto ISO selection. Likewise, the 1/3 stop ISOs can be blocked, which is comfortable for raw shooters.

    Often there is an ultra-low ISO as well, for example 50; that too causes losing one stop from the DR, and that too is treated as "extra".

    However, manufacturers generally are very tight-lipped about anything, which could lead to better understanding of the cameras. For example Nikon never explained in cleartext, what the lossy compression means; they stated only, that in most cases it does not cause any image degradation. Canon do not confirm the method applied in the compression, even though it is known widely (all programs, which are processing Canon raw files on their own have to know the compression).

    Perhaps this is self-generating: all feel, that they would get into a disadvantaged position by revealing some of the restrictions, because others are not revealing that and customers would make a wrong comparison.

    This is happening already. Example: the Canon 1DsMkIII's highest ISO setting is 3200 (I do not know if that is real or fake, I have not seen any raw file yet). Nikon's D3 goes up to 25600. Most Nikon owners herald it as three stop advantage over the Canon, but the D3's 12800 and 25600 are fake. Sometimes I have to laugh reading the owners boosting about the greatness of ISO 25600.

    Anyway, analysis of the raw files, often the histogram alone reveals these tricks. Followings are the fine histograms from the Canon 40D. Each red, green and blue column of pixels in the histogram represents a distinctive pixel level; gaps indicate, that there is no pixel with that level:

    Canon 40D ISO 100

    Canon 40D ISO 125

    Canon 40D ISO 160

    Canon 40D ISO 200

    ISO 3200 (fake) vs 1600 is particularly interesting. The ISO 1600 pixel values get doubled, therefor half of the original pixel values occupy the entire numerical range of the pixel depth. Consequently, pixel values within the top EV of the dynamic range get clipped - without any gain in the shadows.

    The following layered TIFF demostrates the effect:
    Canon40D ISO 1600vs 3200. The file contans the exlanation of the layers.

    The principle is the same for all cameras doing this trick. On the other hand, the "true gain" in details depends on the camera.

    Now, compare the above with the way the Sinar back is operating: higher ISO does not affect the raw pixel data at all. See the histograms of the ISO 100 and 200 shots with the e54: the pixel values reflect the lower exposure with ISO 200. This way the "higher ISO" (which is none) does not induce clipping:

    Sinar e54 ISO 100

    Sinar e54 ISO 200

    (The displayed shutter time is incorrect; Graham has explained, that the camera does not pass this info on the back.)

  9. #59
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    Re: Clearing up confusion with Brumbaer/Sinar backs

    Took this shot this evening while scoping out a location to do a stitched pano. Processed the files in both Exposure and with the Brumbaer software with the latter yielding far better results due to the way it handled the setting sun...

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