[ficofico]

I've a question... nikon have a full frame camera with 12 megapixel and a very good zoom lens, the 14-24 f2,8....

Sony have a 24 megapixel full frame camera and a lens with very great optical design, the samyang 14 f2,8 umc ( also nikon, but I want to consider sony now).



Now, with this example... hom many megapixel remain if I crop the 14mm (24 megapixel file) to a 24mm shot? aproximately?



Thanks

[blende8]

The dependence is linear, so it's 14 MP.

[ficofico]

Whaooo..... a very great 14mm and astonish 24mm without vignetting, with excellent border from f2,8 with 2 other megapixel...... does make sense buy such a lens with a full frame with 12 megapixel? I dont think now



here 14-24 at 24mm





Image a FF camera with EVF and digital zoom directly in EVF...

[Rainer]

[quote name='blende8' timestamp='1295114936' post='5537']

The dependence is linear, so it's 14 MP.

[/quote]



This appears to be wrong.



Lets calculate it:



The formula for the field of view of a rectilinear corrected lens is:



FOV (rectilinear) = 2 * arctan (frame size/(focal length * 2))



So, with a 14mm lens and a fullframe camera, we get



FOV-horizontal = 2 atan( 36 / ( 2*14) ) = 104 degrees



With a 24mm lens, we get



FOV-horizontal = 2 atan( 36 / ( 2*24) ) = 74 degrees



With that, lets calculate, at which framnesize the 14mm lens projects the 74 degrees ...



74 deg = 2 atan( xx / (2*14) )

37 = atan( xx / (2*14) )

0.75 = xx / (2*14)

xx = 0.75 * 2 * 14 = 21mm



Ok ... If we take the image of the 14mm lens (36mm wide) and we want to crop it

to an image as if it was from a 24mm lens, we have to crop it at 21mm ...

this is 21/36 = 58 percent of the image (or factor 0.58) ... but we also have to

crop the heights accordingly ... so, the Megapixels are reduced by the square of 0.58

which is 0.34x ... so from the original 24mpix you are left with only 8mpix.



Just my 2 cts...Rainer

[Brightcolours]

[quote name='Rainer' timestamp='1295116608' post='5540']

This appears to be wrong.



Lets calculate it:



The formula for the field of view of a rectilinear corrected lens is:



FOV (rectilinear) = 2 * arctan (frame size/(focal length * 2))



So, with a 14mm lens and a fullframe camera, we get



FOV-horizontal = 2 atan( 36 / ( 2*14) ) = 104 degrees



With a 24mm lens, we get



FOV-horizontal = 2 atan( 36 / ( 2*24) ) = 74 degrees



With that, lets calculate, at which framnesize the 14mm lens projects the 74 degrees ...



74 deg = 2 atan( xx / (2*14) )

37 = atan( xx / (2*14) )

0.75 = xx / (2*14)

xx = 0.75 * 2 * 14 = 21mm



Ok ... If we take the image of the 14mm lens (36mm wide) and we want to crop it

to an image as if it was from a 24mm lens, we have to crop it at 21mm ...

this is 21/36 = 58 percent of the image (or factor 0.58) ... but we also have to

crop the heights accordingly ... so, the Megapixels are reduced by the square of 0.58

which is 0.34x ... so from the original 24mpix you are left with only 8mpix.



Just my 2 cts...Rainer

[/quote]

All that for only 2 cents? Boy, that is a steal!

[genotypewriter]

[quote name='gianluca' timestamp='1295114133' post='5536']

I've a question... nikon have a full frame camera with 12 megapixel and a very good zoom lens, the 14-24 f2,8....

Sony have a 24 megapixel full frame camera and a lens with very great optical design, the samyang 14 f2,8 umc ( also nikon, but I want to consider sony now).



Now, with this example... hom many megapixel remain if I crop the 14mm (24 megapixel file) to a 24mm shot? aproximately?



Thanks

[/quote]

Hmm I much rather use the 24L II or the TS-E 24L II on a 5D2 ;D



Also, don't forget... the 12MP from the entire sensor is better than 12MP from the cropped area... just like in the case of a 12MP FF vs. a 12MP APS-C.



GTW

[Brightcolours]

[quote name='gianluca' timestamp='1295116315' post='5539']

Whaooo..... a very great 14mm and astonish 24mm without vignetting, with excellent border from f2,8 with 2 other megapixel...... does make sense buy such a lens with a full frame with 12 megapixel? I dont think now



here 14-24 at 24mm





Image a FF camera with EVF and digital zoom directly in EVF...

[/quote]

EVF's are not something nice, in my opinion. I will prefer an OVF anytime. Less "flat" feel to the view, more dynamic, no clipping in dark or light areas, no shot info in the frame itself, no problems seeing nothing with studio flash photography... EVF as option, sure. As OVF replacement, no thank you.



As 14mm, the Samyang is a very interesting low priced option (if you can deal with the distortion). I would certainly take it into consideration. Not as 24mm lens by cropping, though, as it is nearly impossible for me to imagine how to frame that 24mm field of view well.



If I had a Sony FF camera, I would get that 14mm Samyang, and the Sony/Zeiss 24mm f2 for 24mm shots. With full resolution, with easy framing of the shot.

http://www.opticallimits.com/sonyalphaff/568-zeiss24f2ff



And with 12mm extension tube, for 24mm wide angle macro!

http://thkphoto.com/products/kenko/slrc-04.html



If that Sony/Zeiss 24mm f2 is too expensive, I would consider the quite good (especially for the price!) Sigma 24mm f1.8 EX DG macro. Not a real macro lens (even though it has macro in its name), but with 12mm extension tube you can get super close.

http://www.sigmaphoto.com/shop/24mm-f18-ex-dg-asp-macro-sigma



You might by now be wondering why I am blahblah-ing about wide angle macro... Well, as I said, "I" would get a 24mm lens. That was about "my" preference, not necessarily yours. And I happen to love wide fields of view with macro:

[genotypewriter]

[quote name='Rainer' timestamp='1295116608' post='5540']

This appears to be wrong.



Lets calculate it:



The formula for the field of view of a rectilinear corrected lens is:



FOV (rectilinear) = 2 * arctan (frame size/(focal length * 2))



So, with a 14mm lens and a fullframe camera, we get



FOV-horizontal = 2 atan( 36 / ( 2*14) ) = 104 degrees



With a 24mm lens, we get



FOV-horizontal = 2 atan( 36 / ( 2*24) ) = 74 degrees



With that, lets calculate, at which framnesize the 14mm lens projects the 74 degrees ...



74 deg = 2 atan( xx / (2*14) )

37 = atan( xx / (2*14) )

0.75 = xx / (2*14)

xx = 0.75 * 2 * 14 = 21mm



Ok ... If we take the image of the 14mm lens (36mm wide) and we want to crop it

to an image as if it was from a 24mm lens, we have to crop it at 21mm ...

this is 21/36 = 58 percent of the image (or factor 0.58) ... but we also have to

crop the heights accordingly ... so, the Megapixels are reduced by the square of 0.58

which is 0.34x ... so from the original 24mpix you are left with only 8mpix.



Just my 2 cts...Rainer

[/quote]

Uhhh...



14mm = 104.3 degrees (horizontal)

24mm = 73.7 degrees (horizontal)



Assuming 24MP = 6000x4000 pixels,

6000/(104.3/73.7) ~= 4240 pixels wide

Therefore, at a 3:2 aspect ratio the image would be ~= 4240x2827 = 11986480 pixels = 11.99MP ~= 12MP



But as I said... 12MP from 864mm[sup]2[/sup] (FF area) is likely to be better than 12MP from 431mm[sup]2[/sup] (the cropped area on the 24MP FF sensor).



GTW

[blende8]

I don't know what you are calculating, Rainer.

Focal length is proportional to HFoV.

If you double the FL you get twice a much on your image.

[Brightcolours]

[quote name='blende8' timestamp='1295119677' post='5546']

I don't know what you are calculating, Rainer.

Focal length is proportional to HFoV.

If you double the FL you get twice a much on your image.

[/quote]

That is how we calculate equivalent focal lengths with different sized sensors, anyway.