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12-30-2015, 04:02 PM   #136
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But DOF is not a factor in exposure, as are f-stop, shutter speed, and ISO. DOF, as I see it, is not a factor in the amount of light being transmitted. For any given f-stop and shutter speed, we are going to transmit a certain amount of light through the lens. Why does this quantity of light translate to such vastly different noise figures?
But the FF sensor is twice the size. An FF sensor collects twice as much light as an APS-c sensor at the same ƒ-stop, and shutter speed and ISO. Even shooting APS-c light intensity matters (look up reciprocity). I've noticed that at the same ISO an APS-c image will have more noise shot in low light at a longer shutter speed, than shot in bright light at a fast shutter speed. The light is more intense. When you normalize for DoF, you collect the same amount of light. ƒ8 with a sensor double the size, ƒ5.6 with a sensor half the size. Collect the same amount of light, and you have the same s/n ratio.


Last edited by normhead; 12-30-2015 at 04:57 PM.
12-30-2015, 04:08 PM   #137
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QuoteOriginally posted by normhead Quote
But the FF sensor is twice the size. An FF sensor collects twice as much light as an APS-c sensor at the same -stop, and shutter speed and ISO. Even shooting APS-c light intensity matters (look up reciprocity). I've noticed that at the same ISO an APS-c image will have more noise shot in low light at a longer shutter speed, than shot in bought light at a fast shutter speed. The light is more intense. Wen you normalize for DoF, you collect the same amount of light. 8 with a sensor double the size, 5.6 with a sensor half the size. Collect the same amount of light, and you have the same s/n ratio.
I still have some skepticism around this. My brain tells me that the primary driver here is the pixel size and sensor generation. Two sensors of the same generation with similar pixel sizes will perform the same. Typically APSC sensors have had smaller pixels than FF so this notion is accurate in that the collection sites are larger on the FF generally. Interpolation can of course make this better than that implies.
12-30-2015, 04:19 PM   #138
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QuoteOriginally posted by UncleVanya Quote
I still have some skepticism around this. My brain tells me that the primary driver here is the pixel size and sensor generation. Two sensors of the same generation with similar pixel sizes will perform the same. Typically APSC sensors have had smaller pixels than FF so this notion is accurate in that the collection sites are larger on the FF generally. Interpolation can of course make this better than that implies.
With the same lens (not "equivalent FL") on an APS-C and a 35mm sensor, the illumination levels (ie light density or light energy per unit area) will be identical at the same f-stop setting. It's only when people start trying to deal with equivalence based on circles of confusion that things start getting confused (pun intended).
12-30-2015, 04:22 PM   #139
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Should St. Thomas Aquinas miraculously be resurrected even he would not resolve this question.

12-30-2015, 04:36 PM   #140
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QuoteOriginally posted by monochrome Quote
Should St. Thomas Aquinas miraculously be resurrected even he would not resolve this question.
That is likely true as it is unlikely he would be up on the latest technology...
12-30-2015, 05:09 PM   #141
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QuoteOriginally posted by UncleVanya Quote
That is likely true as it is unlikely he would be up on the latest technology...
dude.

Angels. A Pin.
12-30-2015, 05:15 PM   #142
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QuoteOriginally posted by RobA_Oz Quote
light density
Photons are massless - by definition, density is a property that only particles with mass posses.
12-30-2015, 05:44 PM   #143
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In physics terminology, there are definitions of densities that involve mass and there are those that do not (eg. see https://en.wikipedia.org/wiki/Density_%28disambiguation%29), but anyways the standard term of 'lux' is what was intended as the measure of illuminance on the sensor surface, I imagine.

12-30-2015, 06:11 PM   #144
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Photons are massless but behave as waves and particles
12-30-2015, 07:21 PM   #145
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QuoteOriginally posted by monochrome Quote
Should St. Thomas Aquinas miraculously be resurrected even he would not resolve this question.
453.4 small pixels can fit on the head of a pin. But you are better off if you limit the number to 300 larger pixels and use a new pin.
12-30-2015, 07:26 PM - 1 Like   #146
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QuoteOriginally posted by indy Quote
453.4 small pixels can fit on the head of a pin. But you are better off if you limit the number to 300 larger pixels and use a new pin.
You mean a Full Head pin?
12-30-2015, 07:33 PM - 1 Like   #147
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So, 10 pages into this thread we find out it all comes down to pinheads...fantastic!
12-30-2015, 08:09 PM   #148
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QuoteOriginally posted by normhead Quote
You mean a Full Head pin?
Yes...we must remain small and humble. To think or speak of 5x8 would be prideful. Only the engineer knows the answer to things greater than Full Head.
12-30-2015, 08:20 PM   #149
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30.11.2015 = History of Pentax and FF
11.12.2015 = K-mount compatibility explained
24.12.2015 = Crop modes explained
05.01.2016 = ??????
12-30-2015, 08:31 PM - 2 Likes   #150
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QuoteOriginally posted by bxf Quote
Nikon D810 and Pentax k-5 have very similar pixel pitch...
Thank you for making my point, Bxf.

They are very similar.

It's possible the 810 is just made from a bigger slice of the K-5 wafer.

Have a look at how close their noise performance is in on DXOMark - go to 'Measurements', 'SNR 18%', 'Screen'.

http://www.dxomark.com/Cameras/Compare/Side-by-side/Nikon-D810-versus-Pentax...___963_914_830

Use the 'Screen' tab, not the 'Print' tab, since the latter only involves the software noise reduction when they downsample to their 8Mp reference. (This is simply due to the megapickle count. A K-3 benefits more from this than a FF A7S or Canon 1Dx.)

Sensor size does *not* affect noise performance, whatever you've read other people post in other threads, over many years, I bet.

Numbers and size of pixels, circuitry design and suppression of heat/stray currents do.

Last edited by clackers; 12-30-2015 at 08:37 PM.
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