Can you clear something up for me

Soldato
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Hi Guys,

My mum recently brought me a Sigma 35mm F1.4 art for my belated christmas present.

Currently its mounted to a APS-C (pentax K3ii) am i right in think that this lens is actually a full frame lens so I should be treating it as a 52 odd mm lens instead of a 35mm?

so confused as i want to buy a new prime lens for portrait photography /Travel and dont want to double up on either 35mm or 50.

cheers
 
It's physically a 35mm lens whatever camera you mount it on. Full-frame only means it has an image circle large enough to cover the larger sensor. As Raymond says, it gives a field of view equivalent to a 50(ish)mm lens when used on an APS-C camera; it doesn't somehow magically become a 50mm.
 
It's physically a 35mm lens whatever camera you mount it on. Full-frame only means it has an image circle large enough to cover the larger sensor. As Raymond says, it gives a field of view equivalent to a 50(ish)mm lens when used on an APS-C camera; it doesn't somehow magically become a 50mm.

Yes, what I was trying to figure out if it's getting me an equivalent off 50mm their is no point in me spending £600 odd quid on a 55mm lens designed for a apsc camera.

Not sure I could warrant that extra 3mm with the missus :)
 
Whatever the mount of the lens is, that's separate from the focal length of the lens.

A 55mm lens designed for an APS-C camera will still give the equivalent field of view as 82.5mm.
 
Yes, what I was trying to figure out if it's getting me an equivalent off 50mm their is no point in me spending £600 odd quid on a 55mm lens designed for a apsc camera.

Not sure I could warrant that extra 3mm with the missus :)
You're still not getting it. A 55mm lens is a 55mm lens whatever you mount it on but, as Razor-BladE says, on APS-C it will give you the field of view close to an 85mm lens.
 
You're still not getting it. A 55mm lens is a 55mm lens whatever you mount it on but, as Razor-BladE says, on APS-C it will give you the field of view close to an 85mm lens.

Yes if I get a full frame lens of 55mm will give me a field of view of 85mm. But is this the same for a crop sensor based lens? I would have thought a 55mm lens for a crop sensor would be 55mm on a apsc camera.

So the full frame 35mm is giving me on the Apsc a view of 52 odd mm.
 
Yes if I get a full frame lens of 55mm will give me a field of view of 85mm. But is this the same for a crop sensor based lens? I would have thought a 55mm lens for a crop sensor would be 55mm on a apsc camera.

So the full frame 35mm is giving me on the Apsc a view of 52 odd mm.


Yes it's exactly the same for a crop based lens.

Your sensor has a crop factor of 1.5x so ANY lens you use on it is multiplied by 1.5 so a 55mm f/1.4 becomes a 82mm f/2.1 lens in terms of focal length and depth of field.
 
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