So how does this work then?

[pikey]

Some text related to a (used) 75-300mm F4.5-5.6 lens I'm looking at:

"Compatible with all Dynax bodies including the digital 7D, 5D and the Sony Alpha A100 where it will give a range of 115mm to 450mm"

Why would it give a range of 115 to 450mm on the Sony (or are they talking about the Sony + Minolta 7D / 5D as well)?

[Gemm]

I think the crop factor for those cameras is 1.5x, so the lens can effectively give 115-450mm.

And yes, I think they are talking about Sony and Minolta.

Edited by Gemm on Wednesday 17th January 15:54

[pikey]

Gemm said:

I think the crop factor for those cameras is 1.5x, so the lens can effectively give 115-450mm

Thanks. What's a crop factor though?

[Graham@Edinburgh]

The sensors aren't full frame, they're 70% or so, taken from the centre, compared to fullframe. So whereas a fullframe camera taking a picture with a 50 mm lens would include, say, the two trees on the extreme outsides of the picture, the 1.5 sensors would miss those out.

God, that's a crap explanation. Hang on, I'm sure there'll be something pictoral somewhere...

[Graham@Edinburgh]

http://photography-on-the.net/forum/s

[pikey]

Ah, okay, I get it now!

Blue bit is digital, red is film:

[Graham@Edinburgh]

pikey said:

Ah, okay, I get it now!

Blue bit is digital, red is film:

Well, no, it's not that simple Tehre are digital full frame sensors (Canon 5D) and there are 1.3 crops (1d) and 1.6 crops (300D) to give a few examples. Film is always fullframe though, yep.

But the "crop factor" (it's actaully not technically the right term, but serves a purpose) gives the impression that the focal length is longer.

Edited by Graham@Edinburgh on Wednesday 17th January 16:46

[pikey]

Graham@Edinburgh said:

Well, no, it's not that simple Tehre are digital full frame sensors (Canon 5D) and there are 1.3 crops (1d) and 1.6 crops (300D) to give a few examples. Film is always fullframe though, yep.

I'm a beginner and have a small brain, so I'll go with that for now.