FF vs crop sensor perspective

[Jamie Medford]

Hey all, I hoping you can help me figure something out. I know perspective distortion changes depending on the focal length of the lens and with longer lenses the ability to create those lovely smooth uncluttered backgrounds. Now if you compare a 600mm lens on a full frame against a 400mm on a crop frame (1.5), shooting the same subject at the same distance that fills the frame, but different aperatures to obtain the same DoF, will the perspective be the same?...or to put it simplier, can you theoretically obtain the same image excluding other variables such as lens quality, pixel quality etc...Many thanksJamie

[Roger Clark]

Hey all, I hoping you can help me figure something out. I know perspective distortion changes depending on the focal length of the lens and with longer lenses the ability to create those lovely smooth uncluttered backgrounds. Now if you compare a 600mm lens on a full frame against a 400mm on a crop frame (1.5), shooting the same subject at the same distance that fills the frame, but different aperatures to obtain the same DoF, will the perspective be the same?...or to put it simplier, can you theoretically obtain the same image excluding other variables such as lens quality, pixel quality etc...Many thanksJamie

Perspective changes when you change location, not focal length. So to answer your question, the perspective will be the same for the 600+FF versus 400+1.5x crop body assuming both images are made from the same location. But, unless the aperture diameters are the same, the apparent depth of field will be different (assuming the megapixel count remains the same and the enlargement, e.g. 8x10-inch print, remains the same). So if you used a 600 f/4 (150 mm diameter aperture), you would need a 400 f/2.8 (143 mm diameter aperture) to get close to the same depth of field with the 400 on the crop body.

Roger

[Jamie Medford]

Thanks Roger, I've pondered on this days, easy when explained.