Need Help With Pixel Math

[Arthur Morris]

This topic always confuses me. Can someone help with the pixel math comparing the 1D IV--16mp with the APS-H sensor size and the accompanying 1.3 crop factor with the 5D Mark III--22.3mp with a full frame sensor.

[Doug Brown]

I think you'd need 27 megapixels on a 5D3 to get the same pixel density of a Mark IV.

[Arthur Morris]

Thanks Doug but I need someone to show me how to go the math :).

[Don Nelson]

Artie
5DIII has sensor size 36x24 (mm) --> area 864mm2
1DMkiv has sensor size 27.9x18.6 --> area 518.94mm2

Area of 5DIII covered by the on sensor image size of the 1DMkIV is 518.94/864 --> 60.0625% of the 5DIII sensor ( or a 1/0.060625 = 1.664932x factor) . So that's the percentage of the sensor area that will have to have the same pixel density as the MkIV, except we have to figure out what the overall sensor must be....

Now we will force the 5DIII to have the same pixel density as the MkIV but in the larger sensor area:

1D MkIV is 4896x3264 pixels --> 15,980,544 pixels

15,980,544 * 1.664932 --> 26.606535 MP sensor for the 5DIII would be required to achieve the pixel density from the smaller/higherMP APS-H 1DMkIV image area projected onto the new 5DIII sensor.

So, 26.6MP (rounding up, as Doug has done, yields 27MP)

Don

[arash_hazeghi]

easy way: multiple 1D4 Mpixel by crop factor squared i.e. 16X 1.3 X 1.3 = 27

if you want more accurate results (because manufacturers round up mega pixels) use ( 5D3 pixel pitch/ 1D4 pixel pitch) ^ 2 X 100 = (6.08 um / 5.6 um) ^ 2 x100 ~ 118%. i.e. 1D4 has 18% more pixel density.


What do you want to use this number for anyway?

[annmpacheco]

the lottery! excellent math skills fellas!

[Arthur Morris]

easy way: multiple 1D4 Mpixel by crop factor squared i.e. 16X 1.3 X 1.3 = 27

if you want more accurate results (because manufacturers round up mega pixels) use ( 5D3 pixel pitch/ 1D4 pixel pitch) ^ 2 X 100 = (6.08 um / 5.6 um) ^ 2 x100 ~ 118%. i.e. 1D4 has 18% more pixel density.


What do you want to use this number for anyway?

Thanks Don and Arash. Why the question? Folks are constantly asking if they should switch from a 1D IV to a 5D III. So it seems that pixels on the subject (which is directly related to the pixel math (at least as I understand it) is an important part of that equation....

Is this statement correct: the pixels on the subject advantage fir the 1D IV over the 5D III is 22.7% ? (5/22)

I do realize that there are many other factors involved. I will start another thread in Gear and post that link here?

[Arthur Morris]

ps: not everyone can afford a 1 D X. That leads to another question: now that the 5D III AFs at f/8, which is a better camera for photographing perched or standing birds, the 1D X or the 5D III? Which is a better value? Those questions obviously must consider the roughly 37.5% pixel advantage and the vastly lower price of the 5D III....

Arash, do you own a 5D III?

[arash_hazeghi]

Thanks Don and Arash. Why the question? Folks are constantly asking if they should switch from a 1D IV to a 5D III. So it seems that pixels on the subject (which is directly related to the pixel math (at least as I understand it) is an important part of that equation....

Is this statement correct: the pixels on the subject advantage fir the 1D IV over the 5D III is 22.7% ? (5/22)

I do realize that there are many other factors involved. I will start another thread in Gear and post that link here?

nope

First of all it is 18% not 22.

secondly, resolution does not correlate to pixel on the subjects linearly. If you want to increase resolution let say from 50 lpm to 100 lpm you need to double pixel density in both x and y meaning you will have to quadruple the number of pixels, i.e. go from 20Mpicxel to 40Mpixel. a 18% increase in pixel density is only 9% increase in resolution.

can you make a careful test to show the difference? yes

does it make a meaningful difference in the field? no in my experience.



I did own a 5D3 but I recently sold it because I had not touched since getting the 1DX.

[Miguel Palaviccini]

Neat subject. Arash is spot on. BTW, did you mean 20 Mpx to 80 Mpx?

[Loi Nguyen]

Pixel density = 16/(27.9*18.6) = 0.031Mpixels/mm2 for 1DV
Pixel density = 22.3/(36x24) = 0.026 Mpixels/mm2 for 5D3

1DV has 5/26 advantage in terms of pixel density or ~ 18%. Same answer as Arash's calculations, but may be easier to explain why there is the square factor.


The 1.3 crop factor comes from 36/27.9 = 1.3
and 24/18.6 = 1.3.

Thus the pixel density calculation is proportional to the square of the crop factor.

I didn't think clearly myself until going thru the calculation and read the comments above.

So, may be I should run out and buy a used copy of the 1DV before it all disappear after your blog, Artie :)

Loi

[arash_hazeghi]

Neat subject. Arash is spot on. BTW, did you mean 20 Mpx to 80 Mpx?

yes 80 sorry