FF, FX and DX... Effects on Lens?

sophos9

sophos9

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Dave
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Sanity check please...Do I have this right?

A Canon d5 is full frame - a Nikon D80 is cropped. A 50mm lens on a FF (or Nikon FX) is a true 50mm where a 50mm on a cropped body is actually 80mm (due to the cropped multiplier of 1.6x)

So, on the above assumptions. If I wanted to mimic a 18-30mm picture from a FF or FX, I would actually need a 11-19mm on a cropped body.

Correct or not?
 
sophos9 said:
Sanity check please...Do I have this right?

A Canon d5 is full frame - a Nikon D80 is cropped. A 50mm lens on a FF (or Nikon FX) is a true 50mm where a 50mm on a cropped body is actually 80mm (due to the cropped multiplier of 1.6x)
Click to expand...
Almost. It will still be a 50mm lens in terms of focal length and depth of field, however it will give the same field of view as an 80mm lens


So, on the above assumptions. If I wanted to mimic a 18-30mm picture from a FF or FX, I would actually need a 11-19mm on a cropped body.

Correct or not?
Click to expand...
100% Correct
 
Wonderful... thanks for confirming!

Next question - does anyone know of any good optics for ranging around 11-19mm??

Anyone have a Tokina 11-16mm f2.8?
 
I have neither of those but I do have a Sigma 12-24. Not quite as wide as the Tamron or Tokina but still fairly wide and has the major advantage of being FF/35mm compatible as well. Some people also swear by their Sigma 10-20mm lenses if they've got a good copy - those with bad copies swear AT the lenses!
 
RichardtheSane said:
Almost. It will still be a 50mm lens in terms of focal length and depth of field, .......
Click to expand...

Correct me if I'm wrong, but doesn't the depth of field change?

What I mean; an FX with a 50mm at f/1.8 will have a shallower dof than a DX with a 50mm at f/1.8 :shrug: ?!?
 
Wail said:
Correct me if I'm wrong, but doesn't the depth of field change?

What I mean; an FX with a 50mm at f/1.8 will have a shallower dof than a DX with a 50mm at f/1.8 :shrug: ?!?
Click to expand...

A full frame camera will have a shallower depth of field than the equivalent crop camera.
 
The depth of field will not change. This is a physical property of the lens.

You are correct in thinking the final image will appear to have more depth of field, but this is because the centre portion of the image the lens produces is being magnified on the crop body.

If you were to put a full frame camera on a tripod with a 50mm lens and take a shot, then from the same position put a crop camera on the tripod with a 50mm nothing had changed optically.
So on the computer crop the image from the full frame camera to have the same field of view as the crop camera. The resulting images when viewed side by side will be exactly the same.

There is some heavy reading out there about Circle of Confusion that explains this in more detail - I've not found anywhere that explains that very well and while I understand it I have difficulty explaining it too!
 
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