Help on non digital lenses

what make, aperture?
lens and camera, that is
 
I have read somewhere (can't remember where) that a 50mm focal length for a 35mm lens equates to around 75-80mm on dslr.

I have no idea how this is worked out. :shrug:
 
Not sure I understand, a 28-70 will always be a 28-70. Regardless of whatever camera you use :)
 
dazzajl said:
Not sure I understand, a 28-70 will always be a 28-70. Regardless of whatever camera you use :)
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Depending on the crop factor of the DSLR, For Canon 400D's and similar, it is not full frame and only produces a portion of the image, this is equilavent to having a 44.8-112mm lens, due to the 1.6 crop factor.

On film the lenses will be the same, on digital this is different, but you've not really included any details so I can't really help you, what camera have you got?

Canon 400D/350D/300D/40D/30D/20D = x1.6 Crop Factor (so multiply both numbers)
Canon 5D = Full Frame, no change.
 
asab said:
Dazzajl now explain it properly :)
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Do I have to? :LOL:

It would be much easier to see what the real question is first. ;)
 
neillewi said:
So if i stick a 70-300 film lens on my Canon 400D it will be a 112-480 instead.
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No.

It will still be a 70-300 but your picture will be smaller.

Imagine a room with a chair and a window. If you sit in the chair and look out of the window you can see a part of the world outside. If you change the window for one 1.6 times smaller, you will see less of the world. The relationship between you and the stuff outside has not changed.

Changing from a 70 to a 112 lens would be more like keeping the window the same and moving the chair backwards.

Similar but in the world of physics and photography, totally different.
 
lol, this subject can get so confusing (even though it shouldn't) :p

The longer the focal length of a lens, the smaller the field of view (how much you can see through it). For example, if you had a 200mm lens on a dslr with a crop factor of 1.5, you would have to put a lens 1.5 times that length on a full frame camera to achieve the same field of view. Hence a 200mm lens on a dslr is equivalent to a 300mm lens on a 35mm camera.

It has everything to do with how much of the shot you can see and nothing to do with magnification :p .......cropped sensors have a lot to answer for...
 
dazzajl said:
No.

It will still be a 70-300 but your picture will be smaller.

Imagine a room with a chair and a window. If you sit in the chair and look out of the window you can see a part of the world outside. If you change the window for one 1.6 times smaller, you will see less of the world. The relationship between you and the stuff outside has not changed.

Changing from a 70 to a 112 lens would be more like keeping the window the same and moving the chair backwards.

Similar but in the world of physics and photography, totally different.
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Say you had a 70-300 on a cropped sensor and a film slr body next to each other. While the film camera would see all of the image at 70mm, the crop body wouldn't see the outer edges, the angle in view is less so in effect what you can see is equivalent to what the film body would see at 112mm.

That's the way I understand it. Physically the objects are the same distance apart but due to the lower angle and smaller size it effectively becomes that of the higher focal length. no?
 
Physically the objects are the same distance apart but due to the lower angle and smaller size it effectively becomes that of the higher focal length. no?
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There are three aspects of lens characteristics that change with focal length. Field of view is one but it's not the defining factor, to me anyway.

The amount of compression or distortion and the depth of field qualities will remain exactly the same regardless of the size of the sensor or film and to me at least, these are most of what defines a lenses nature.
 
which begs the question .. what is the true ( correct ? ) size of a photograph ?
 
Whenever I see a thread like this, I feel it must be time to wheel out my visualisation again.

Crop-factor-demo-3.jpg


The left-hand image simulates the view through a lens designed for film or full-frame digital SLRs (an EF lens in Canon-speak). The different rectangles show you how much of the view you can see with different types of camera.

The right-hand image simulates the view through a lens with the same focal length designed for small-sensor digital SLRs (an EF-S lens in Canon-speak). I don't think you could actually mount this on a full-frame camera, but anyway, the rectangles show you how it would look if you could.
 
StewartR said:
Whenever I see a thread like this, I feel it must be time to wheel out my visualisation again.
Click to expand...
A very simple image, but seeing that the explanations in the rest of the thread now make perfect sense to me, thanks a lot :)
 
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