D7100 1.3x crop - Is it my math or...

Started Jun 17, 2013 | Questions
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Suhas Sudhakar Kulkarni
Suhas Sudhakar Kulkarni Regular Member • Posts: 259
D7100 1.3x crop - Is it my math or...

Nikon claims on their website that 1.3x crop gives 15.4 MP image.

http://imaging.nikon.com/lineup/dslr/d7100/features01.htm#a10

However, If I calculate:

1.3x1.3=1.69

24/1.69=14.20MP approx.

Which one is correct?

Also 1.5x1.3 would give total crop of 1.95x and not 2x as specified by Nikon.

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Suhas
website: photo.net/photos/suhaskulkarni

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BirgerH
BirgerH Senior Member • Posts: 4,091
Re: D7100 1.3x crop - Is it my math or...

Suhas Sudhakar Kulkarni wrote:

Nikon claims on their website that 1.3x crop gives 15.4 MP image.

http://imaging.nikon.com/lineup/dslr/d7100/features01.htm#a10

However, If I calculate:

1.3x1.3=1.69

24/1.69=14.20MP approx.

Which one is correct?

Also 1.5x1.3 would give total crop of 1.95x and not 2x as specified by Nikon.

-- hide signature --

Suhas
website: photo.net/photos/suhaskulkarni

Because:

1.5 crop is not exactly 1.5 crop. With the D7100 it is 1.53518 if you use the relation of 24 x 36mm.

1.3 crop is not exactly 1.3 crop. In relation to 24 x 36 mm it is 1.91744 (aprox. 2)

The "1.3" crop will then be the square root of the Square of 1.9744 divided by the Square of 1.53518, which wil be 1.2490, aprox. 1.3

And then you got aprox. 15.4 MP (24/1.249/1.249).

Thats the math - but why bother - go use it.

BirgerH.

 BirgerH's gear list:BirgerH's gear list
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BirgerH
BirgerH Senior Member • Posts: 4,091
Re: D7100 1.3x crop - Is it my math or...

BirgerH wrote:

Suhas Sudhakar Kulkarni wrote:

Nikon claims on their website that 1.3x crop gives 15.4 MP image.

http://imaging.nikon.com/lineup/dslr/d7100/features01.htm#a10

However, If I calculate:

1.3x1.3=1.69

24/1.69=14.20MP approx.

Which one is correct?

Also 1.5x1.3 would give total crop of 1.95x and not 2x as specified by Nikon.

-- hide signature --

Suhas
website: photo.net/photos/suhaskulkarni

Because:

1.5 crop is not exactly 1.5 crop. With the D7100 it is 1.53518 if you use the relation of 24 x 36mm.

1.3 crop is not exactly 1.3 crop. In relation to 24 x 36 mm it is 1.91744 (aprox. 2)

The "1.3" crop will then be the square root of the Square of 1.9744 divided by the Square of 1.53518, which wil be 1.2490, aprox. 1.3

And then you got aprox. 15.4 MP (24/1.249/1.249).

Thats the math - but why bother - go use it.

BirgerH.

Sorry, missed a 1 in "Square 1.91744"

 BirgerH's gear list:BirgerH's gear list
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Suhas Sudhakar Kulkarni
Suhas Sudhakar Kulkarni OP Regular Member • Posts: 259
Re: D7100 1.3x crop - Is it my math or...

Thanks, that explains. So it is actually 1.917.. crop from full frame and not 2x crop.

Why bother?? Just out of curiosity, I was comparing with Sony smart teleconverter which gives you 2x crop with 12MP image (on A65 / A77).

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Suhas
website: photo.net/photos/suhaskulkarni

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lock
lock Veteran Member • Posts: 6,178
not even that

Look at the hor and vert. Number of pixels. It is a factor of 1.25.

Lock

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BirgerH
BirgerH Senior Member • Posts: 4,091
Re: not even that

lock wrote:

Look at the hor and vert. Number of pixels. It is a factor of 1.25.

Lock

Okay - didn't do that.

It makes a different of size-crop and pixel-crop. Still I can't see any real problem if you want to make Photos.

The D7100 has this extra Facility of cropping - go use it or do not. Math will not give you better Pictures.

BirgerH.

 BirgerH's gear list:BirgerH's gear list
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lock
lock Veteran Member • Posts: 6,178
Of course!

By all means, use it.

Lock

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BirgerH
BirgerH Senior Member • Posts: 4,091
Re: not even that

A factor of 1.25 is in my eyes very close to a factor of 1.249.

 BirgerH's gear list:BirgerH's gear list
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jimoyer
jimoyer Senior Member • Posts: 1,853
Re: D7100 1.3x crop - Is it my math or...

This thread makes my eyes bleed......

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Red5TX
Red5TX Senior Member • Posts: 1,586
Re: D7100 1.3x crop - Is it my math or...

Suhas Sudhakar Kulkarni wrote:

Thanks, that explains. So it is actually 1.917.. crop from full frame and not 2x crop.

Why bother??

Because in crop mode the autofocus points cover virtually the entire frame.

And if you shoot in jpeg + crop, you have (I believe) unlimited buffer depth. There are limited circumstances where those two factors (full af coverage and limitless buffer) might be very handy in combination.

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Erik the Red
Erik the Red Regular Member • Posts: 263
Re: D7100 1.3x crop - Is it my math or...

4800 x 3200 = 15,360,000 pixels, for what it's worth.

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