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02-05-2015, 04:54 AM   #16
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Just for info, this is how Nikon explains crop mode in the 24MP D610 manual:



Note how they say 'an area at the centre is used to record pictures'. So the effect will [probably] not be identical to resampling a full-size 24 MP image down to 10MP.

02-05-2015, 05:23 AM   #17
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I hope we can use our APS-C lenses in non-crop mode and crop in post.
02-05-2015, 08:04 AM   #18
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There's a mix of good and bad math above. FF is approximately 1.5 times larger than APS-C in both height and width. 1.5 * 1.5 = 2.25.

The equivalent focal length just gets scaled by 1.5, but any pixel counts have to be scaled by 2.25.
02-05-2015, 08:17 AM - 1 Like   #19
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QuoteOriginally posted by DeadJohn Quote
There's a mix of good and bad math above. FF is approximately 1.5 times larger than APS-C in both height and width. 1.5 * 1.5 = 2.25.

The equivalent focal length just gets scaled by 1.5, but any pixel counts have to be scaled by 2.25.
I learned something new and I stand corrected from my earlier post! Thanks!

02-05-2015, 02:22 PM   #20
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QuoteOriginally posted by MadMathMind Quote
I get that everything is speculation at this point, since we don't know how Pentax's design will work, but are there benefits to using an APS-C lens on a full frame camera in crop/compatibility mode?

I get that it doesn't make the best use of the full frame sensor. The biggest attraction for me for full frame is the superb high ISO performance it offers. Would that still be retained in compatibility mode? Looking at pixel density, a full frame sensor at 36MP has 33% more pixels than a 24MP sensor but nearly twice the area. The pixel densities are:

16MP APS-C on K-5: 43.752 px/mm^2
24MP APS-C on K-3: 65,641 px/mm^2
36MP FF on K??: 41,666 px/mm^2

If ISO performance is tied to pixel density heavily, then it would mean the FF sensor would only do a bit better than the K-5. (Of course, implementation and the sensor matter *a ton*.) I assume that the performance would still hold in crop mode, no?
The typical 36MP FF cropped to APSC mode will have a bit more than 15MP and the iso performance of a K5. There nothing magical here, this is the same sensor technology and so if you cut it the same size, you get the same performance.

So 36MP FF cropped to APSC mode => K5.
02-05-2015, 04:03 PM   #21
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QuoteOriginally posted by 6BQ5 Quote
I think you mean 24 MP in crop mode? 36 / 1.5 = 24?
Actually the 1.5 is the focal length multiplier, which is based on the diagonal measurement of the the frame. The FF sensor is 2.25 x the area of the Pentax/Nikon asp-c sensor. A 36mp FF sensor is 16mp when cropped to asp-c size. I have been using a 36mp A7R FF for the last year and the 16mp is quite useable. The A7R performs the same as my K5II, since the pixel pitch and generation are the same
02-05-2015, 05:30 PM   #22
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QuoteOriginally posted by MadMathMind Quote
If ISO performance is tied to pixel density heavily
It isn't.
02-14-2015, 02:01 PM   #23
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QuoteOriginally posted by 6BQ5 Quote
I think you mean 24 MP in crop mode? 36 / 1.5 = 24?
No.
crop ff/apsc = 864 / 372,09 = 2,32202
so
36 Mp / 2,3 = 15,5 Mp

16 Mp APS-C in crop-mode from 36 Mp FF.
===

1,5 is a number in crop mode for angle of view from diagonal of sensor
2,3 is a number in crop mode for pixels from area of sensor

===

K-5 sensor: 23.7mm x 15.7mm = 372,1mm^

02-17-2015, 07:28 PM   #24
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Area requires the multiplication of the two dimensions (1.5x1.5 magnification in one dimension = 2.25 magnification factor in two dimensions)
Maths doesn't have to be overly complicated.
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