Focal length of other formats

[peterb533]

This may be a stupid question but I'm going to ask anyway.

I know for an APS-C sensor the focal length in 35mm terms is multiplied by 1.6 or 1.5 for Nikon users and there are similar factors for compact digital cameras, but for medium format film, specifically 6x4.5 and 6x8, is there a factor that can be applied to get the 35mm equivalent. Also how does this affect DOF?

My Fuji GX680 has 65mm, 100mm, 150mm and 300mm lenses (6x8 format) and my ga645zi has a zoom range of 55-90mm (6x4.5 format).

Peter

[Colin Southern]

I know for an APS-C sensor the focal length in 35mm terms is multiplied by 1.6 or 1.5 for Nikon users

Hi Peter,

Just to complicate things even more, the "apparant focal length multiplier" is also "effectively affected" by the relative pixel counts, when comparing two cameras.

Case in point - the Canon 1D3 (10MP) has a crop-factor of 1.3x - but a 21MP 1Ds3 can actually out-resolve it by around 30% (so rather than the 1D3 having a reach advantage, it's actually at a disadvantage when compared to the 1Ds3 (ie you're better off using a 1Ds3 & cropping).

[peterb533]

Hi Peter,

Just to complicate things even more, the "apparant focal length multiplier" is also "effectively affected" by the relative pixel counts, when comparing two cameras.

Case in point - the Canon 1D3 (10MP) has a crop-factor of 1.3x - but a 21MP 1Ds3 can actually out-resolve it by around 30% (so rather than the 1D3 having a reach advantage, it's actually at a disadvantage when compared to the 1Ds3 (ie you're better off using a 1Ds3 & cropping).

Hi Colin,

Thanks for that, which is why I am quite happy with my 5D Mk2 when shooting distant objects. But this doesn't apply here as I'm talking about film cameras and a film has the same resolution whatever the camera, assuming the lens can resolve the image of course.

Peter