Yep, get that now. Am I correct in thinking that dof will change though, i.e. f/8 will give a different dof if you crop the full frame image to the same fov as the APS-C?

Indeed it is, and the key quote is: "two shots of the same scene from the same distance will exhibit identical perspective distortion, regardless of lens used"

Here are the pics (not on a tripod, but on a table, so probably a slight movement on changing lenses - I have to work you know!):

10mm (heavily cropped)




200mm (needed to use f/32 and high iso to get dof)




That Sigma 10-20 is bl**dy good, innit !

Having sat through the theory lessen I took ChrisA's advice and did the practical. Well, proof is in the pudding as they say! I must admit, I had noticed the bit about moving position, but thought that it couldn't make that much difference.

No full-frame for me!!

John

I understand what you're saying, but that isn't what I'm saying, in fact is the other side of the coin! Of course the perspective doesn't change if you don't change the lens, but I'm saying that if you want the same perspective as a 85mm lens in 35mm format in APS-C, then you have to use a 85mm. Your 50mm lens in APS-C will not give you the same perspective as a 75mm lens in 35mm format. Is this correct or not? Or am I just getting more and more confused

Tony

Is this true? See here: http://www.photozone.de/focal-length-and-perspective

Though reading your last sentence I get the feeling that you agree with me? I.e. a 50mm lens will always give a 50mm perspective. I think this is crucial because people talk about the "ideal " portrait lens from film days as being roughly 85mm, so assume their 50mm is pretty much the same. But it was the perspective of the 85mm which is important.?
(I'm going to have a coffee - too much thinking for a Monday morning )

I thought that the KEY difference is dof and perspective. To take it to the extreme, if the sensor was iso 2 million and you had no noise, then you could shoot everything with an ultra-ultra wide 5mm lense and just crop away to get the effective fov you want, but you will always get the perspective of a 5mm lens, i.e. large separation of foreground and background - which probably won't help your portraits (big nose!)

I had an Olympus OM10 in the 80s and when I took up photography again 4 years ago I remember wondering what was missing - the fact is a 50mm APS-C lens is NOT the equivalent of a 75mm full frame lens. It will give the same fov, but not the same picture.

I think !

The first is very good and it looks like you've framed according to rules of thirds. However, in this instance I think the framing would be better with the horizon close to the centre - although this does lead to more of a panoramic aspect. The reason I feel this is better (and having tried it by moving the image on my PC), is that the sky is very uniform and becomes a bit of space filler.

I am of course totally wrong and your canvas print is safe

Can we have a separate geography section in the forum please?

Staying on subject, I prefer the former.

+1 for digital learning. The cost of an *ist DS second hand will easily be covered by the costs quoted above for developing (how much ) and it can then be re-sold later if needed. (No, I'm not selling mine )