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Author Topic: Leaf backs, base iso question.  (Read 2133 times)

klane

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Leaf backs, base iso question.
« on: December 16, 2008, 03:52:47 pm »

I currently own a valeo 17wi and have been thinking about  buying an aptus ii 6 next year, however the new aptus backs start at iso50. The older aptus/valeo backs 17/22 start at 25.

Is the base (native iso) of the older backs 25 or is it 50? If it is 50 then do I lose anything by shooting at 25?


Thanks Kyle
« Last Edit: December 16, 2008, 04:58:06 pm by klane »
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shutay

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Leaf backs, base iso question.
« Reply #1 on: December 16, 2008, 10:48:38 pm »

Quote from: John Schweikert
For most shots 25 or 50 are both so nice that it won't matter. Only on my Aptus22 when raising shadows or exposure or major file massaging will I even notice, if anything at all.

I would add too that I have had experiences in the past where I was worried about noise that had come out in shadow areas of my file (not a Leaf back) on screen at 100% once all the processing was done, but after printing even at fairly large print sizes, we could not really discern the noise at all. So a tiny bit of noise here and there if there is any at all is not a disaster and most of the time at ISO 100 or below the files are so clean anyway.
« Last Edit: December 16, 2008, 10:49:24 pm by shutay »
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Panopeeper

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Leaf backs, base iso question.
« Reply #2 on: December 17, 2008, 12:19:34 am »

Quote from: klane
Is the base (native iso) of the older backs 25 or is it 50? If it is 50 then do I lose anything by shooting at 25?
Caution with the term "base ISO" in conjunction with such cameras/backs, which do not offer real ISO selection (only a few MFDBs do have different ISO implementations).

As the sensor knows only one ISO setting, the ISO selection affects only the metering/exposure calculation. So, the question is, when shooting for example an 18% grey card and the result is 50% brightness, then with which ISO selection does the metering yield that specific exposure. (The 18% and 50% are only examples, I don't know the ISO specs.)

As many if not all manufacturers are cheating with their ISO specification (they make the sensors appear "stronger" than they are), the best would be to shoot a serie with different exposures and compare the results to the metering suggestion.

Back to the question: if the "base ISO" is 50, then shooting @ 25 means 1 EV overexposure and that may cause clipping. However, I doubt that MFDBs offer lower ISOs than the base; there is no point. The other direction is more important: every stop higher ISO means one stop more underexposure and pushing it in post processing. It is amazing, how much pushing the raw images of some MFDBs can bear.
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Gabor

klane

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Leaf backs, base iso question.
« Reply #3 on: December 17, 2008, 12:50:50 am »

Thanks for the insight.  

Pano- are you saying the native iso is actually 25 or is it actually 50?
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yaya

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Leaf backs, base iso question.
« Reply #4 on: December 17, 2008, 02:57:08 am »

Quote from: klane
I currently own a valeo 17wi and have been thinking about  buying an aptus ii 6 next year, however the new aptus backs start at iso50. The older aptus/valeo backs 17/22 start at 25.

Is the base (native iso) of the older backs 25 or is it 50? If it is 50 then do I lose anything by shooting at 25?


Thanks Kyle

Hello Kyle,

The native speed of the 17/22MP Dalsa sensors is 25 iso, however like John has suggested, you will be pushed really hard to notice any differences when using the Aptus/ Valeo 17/22 at 50 iso in terms of noise or DR.

Hope this helps

Yair
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