[nandadevieast]

This lens is reported to be workable on FX cameras with some vignetting, that may not be unwanted in low light or street shots.

D800 has different crop modes. Someone suggested that on 1:2 crop mode this lens could be perfectly usable.

What will be the effective focal length on that crop mode, any idea?

regards,

[IanCD]

[quote name='nandadevieast' timestamp='1332515159' post='16946']

This lens is reported to be workable on FX cameras with some vignetting, that may not be unwanted in low light or street shots.

D800 has different crop modes. Someone suggested that on 1:2 crop mode this lens could be perfectly usable.

What will be the effective focal length on that crop mode, any idea?

regards,

[/quote]



In DX crop mode, it will be 52.5mm equivalent (35mm x 1.5 crop ratio)

In1.2x crop mode, I think it will be 35 x 1.2 = 42mm

Ian

[nandadevieast]

how do you calculate this?

does it mean in 5:4 mode it will be 35x5.4 = 180mm ???

[IanCD]

[quote name='nandadevieast' timestamp='1332599462' post='16984']

how do you calculate this?

does it mean in 5:4 mode it will be 35x5.4 = 180mm ???

[/quote]





Nikon DX crop sensors are cited as having a 'crop factor' of 1.5, so you multiply the FL by 1.5 to get the effective FL in DX

Canon APS-C are said to have a crop factor of 1.6, so you multiply FL by 1.6 to get effective FL for Canon APS-C



Someone else will probably be able to explain the physics behind this better than I can... the cited crop factors are close to the ratio between crop sensor dimensions and the FF sensor...

E.g Nikon 5100 sensor is 23.6 x 15.6mm.; multiply those dimensions by 1.5 and you get 35.4 x 23.4... similarky with Canon APS-C (600D) the dimensions are 22.3 x 14.9; multiply those by 1.6 and you get 35.68 x 23.84

In both cases this is close to 36 x 24, but this may actually be nothing to do with it..!



The Nikon crop sensor gives a field of view equivalent to a lens with 1.5 times the FL; Canon APS-C gives FoV quivalent to lens with 1.6 times FL.



I think 5:4 (crop) mode indicates that the FoV is equivalent to a lens with 1.25x FL so you'd multiply by 1.25 to get effective FL. D800 is cited as having a 1.2x crop factor... not sure why it would be 1.2 rather than 1.25...?

I'm no expert in this... I think this is how it works, but one of the folk here who actually knows this stuff may well correct this..! <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='' />



and note the difference between a 1.2x crop factor and 1:2 ratio which, I think, would give a 2x crop factor

Ian

[dhazeghi]

[quote name='IanCD' timestamp='1332621736' post='17011']

I think 5:4 (crop) mode indicates that the FoV is equivalent to a lens with 1.25x FL so you'd multiply by 1.25 to get effective FL. D800 is cited as having a 1.2x crop factor... not sure why it would be 1.2 rather than 1.25...?[/quote]



No, 5:4 changes the aspect ratio. It uses a 30x24 crop of the sensor. Basically, it crops horizontally, but not vertically. Technically, that's a 1.14x crop factor, since crop is measured by the diagonal.



1.2X uses a ~30x20 crop of the sensor (3:2 aspect ratio), and does indeed result in a 1.2x crop factor.



DH