just when I thought I knew what I was talking about....

2blue4u

2blue4u

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I've just read this on a shop site in respect of the Tokina 11-16

Another interesting lens announced by Tokina is the Tokina 11-16 f2.8 AT-X 116 Pro DX, a wide zoom for Nikon and Canon crop sensor cameras boasting a focal length of 11-16 mm and constant f/2.8 maximum aperture.
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so far, so good. So with my Canon 40D I would enjoy 11-16 mm focal length.


It then goes on -
...this lens is likely to generate considerable interest with its 17-25 mm approx. equivalent focal length (on Nikon DX, Canon APS-C users will get around 18-26 mm).
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:thinking: :shrug:
 
2blue4u said:
I've just read this on a shop site in respect of the Tokina 11-16

so far, so good. So with my Canon 40D I would enjoy 11-16 mm focal length.


It then goes on - :thinking: :shrug:
Click to expand...

It the crop factor on a Dx sensor, the 11-16mm is the angle of view on a full frame, camera 17-25 will be the angle of view of a crop sensor.
 
2blue4u said:
I've just read this on a shop site in respect of the Tokina 11-16

so far, so good. So with my Canon 40D I would enjoy 11-16 mm focal length.


It then goes on - :thinking: :shrug:
Click to expand...

It is described as 11-16mm on 35mm format, but its designed for APS-C sensors meaning on a Nikon (1.5x crop factor) it will have an equivalent focal length of 17-25mm and Canon (1.6x crop factor) 18-26mm.

Edit: Just to make it clear this won't have the same focal length as for example a 17-70mm lens at 17mm. For example that would have an equivalent focal length of 26-105mm....
 
mattyh said:
I'd say it's a bit ambigious, it says it's designed for crop cameras, with the lens focal lengths being 11-16mm, so you'd assume that being designed for a crop sensor, that the focal lengths would be correct. But they're not.
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precisely my point.
 
The only difference between a DX and 35mm format lens is the image circle, which is smaller on a DX lens to allow it to fit the APS-C sensor correctly. The focal length remains the same, the image circle it produces is different. They couldn't exactly name it via any other format as there are so many different crop factors to consider.
 
alexisonfire said:
The only difference between a DX and 35mm format lens is the image circle, which is smaller on a DX lens to allow it to fit the APS-C sensor correctly. The focal length remains the same, the image circle it produces is different. They couldn't exactly name it via any other format as there are so many different crop factors to consider.
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so are you saying that a Canon EF-S 10-22mm won't be a 10-22mm when used on the cameras it is designed for?


/edit - I quite accept that a 24-105 EF will be different when used on a crop sensor. Am I naive to think that the specified focal length should be quoted for the sensor type the lens is actually designed for?
 
2blue4u said:
so are you saying that a Canon EF-S 10-22mm won't be a 10-22mm when used on the cameras it is designed for?
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Nope - what he's (we're) saying is that the lens, any lens, has a given focal length and that doesn't change regardless of the camera it's put on

Quite what view you see through it and record will depend on your camera's format

i.e. on a Medium Format camera a 150mm lens still has a focal length of 150mm, and if you could fit it to a 35mm or cropped sensor camera it would still have a focal length of 150mm - it would just appear different on each camera

DD

EDIT TO YOUR EDIT :lol: - it's always been a measure of the physical property of the lens and has never been 'amended' to different format of cameras
 
2blue4u said:
so are you saying that a Canon EF-S 10-22mm won't be a 10-22mm when used on the cameras it is designed for?


/edit - I quite accept that a 24-105 EF will be different when used on a crop sensor. Am I naive to think that the specified focal length should be quoted for the sensor type the lens is actually designed for?
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A 10-22mm DX lens was designed for the APS-C sensors to give the same focal length of 15-33mm on 35mm (fullframe).
 
alexisonfire said:
A 10-22mm DX lens was designed for the APS-C sensors to give the same focal length of 15-33mm on 35mm (fullframe).
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Now that's getting confusing :lol:

The 10-22mm lens is still a 10-22mm lens, the only difference for the DX format is that it's actually smaller in size, and the crop factor gives an apparent increase in focal length as it's only using what would be the middle bit of a bigger lens

DD
 
I think they are just trying to say it will give the equivalent field of view as a 17-25mm lens would on a 35mm (full frame) camera
 
That's exactly what he's saying. Lens focal lengths are still shown in 35mm terms and unless you have a full frame DSLR you will have to factor in the croping of most DSLR's to dertermin the affective focal length of your lens.
 
tonyfish said:
That's exactly what he's saying. Lens focal lengths are still shown in 35mm terms and unless you have a full frame DSLR you will have to factor in the croping of most DSLR's to dertermin the affective focal length of your lens.
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Sorry, but no

We are more used to discussing focal lengths in relation to 35mm that's all - it has no bearing on the film, sensor size

No-one re-adjusts the focal length for 6x6 cm cameras do they, we all just know that a 85mm lens on a 6x6 is not the same field of view as an 85mm on a 35mm, which is different again to a cropped sensor. My mentioning 35mm of whatever you're talking about the camera, not the lens

DD
 
So we're saying that a Canon EF-S 10-22mm is only 10-22mm if and when fitted on a full frame camera which it couldn't, wouldn't and wasn't designed for.
 
2blue4u said:
so are you saying that a Canon EF-S 10-22mm won't be a 10-22mm when used on the cameras it is designed for?


/edit - I quite accept that a 24-105 EF will be different when used on a crop sensor. Am I naive to think that the specified focal length should be quoted for the sensor type the lens is actually designed for?
Click to expand...

it is 10-22mm and if you were able to stick it on a full frame sensor body it would be 10-22mm...put it on a crop sensor body and it equates to 16-35mm ish. I should imagine the parameters that define a lens make it 10-22mm, but it's the crop sensor which creates the ambiguity so lens manufacturers are perhaps correct in their description in that sense. I doubt though, that anyone would complain if they stated the effective focal length.
 
Same thing with compacts...I bought a G10, and it has a lens of 6.1mm -30.5mm

BUT, the 35mm equivalent is 24 - 140 (or is it 28-140? I forget)

Be some trick to have a lens designed that is 6 - 30mm!
 
2blue4u said:
So we're saying that a Canon EF-S 10-22mm is only 10-22mm if and when fitted on a full frame camera which it couldn't, wouldn't and wasn't designed for.
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But because its designed for APS-C sensors the image circle would not fill the full frame sensor.
 
Have a look here its all explained with pictures- its the field of view thats different between full frame and Cropped sensor the physical focal length ie 10-22mm is always 10-22mm regardless of what its fitted to.
 
Let's try an analogy - see if this makes it any clearer

Pick a window in your home, and look through it from 3 ft away - you can see far to each side and up and down can't you

Now walk to 6ft away, you can't quite see as far up or wide now but the window is still the same size

If you can, move 12ft away - the window is still the same size, but your viewpoint has changed and you can't see as much either wide or tall

You moving is a bit like changing sensor size, the lens is still the same lens and it still has the same focal length - only the view has changed

A DX lens won't work properly on a FF camera as the window isn't wide enough to let light into all of the FF sensor; just as a larger lens suited to a FF sensor won't work properly on a medium format camera, as again it's window of light isn't big enough

Does that make more sense?

DD
 
I fully accept and understand that. I was under the misapprehension that EF-S (and the like) lenses would have their 'effective' focal length specified for the systems on which they would be used.
 
2blue4u said:
I fully accept and understand that. I was under the misapprehension that EF-S (and the like) lenses would have their 'effective' focal length specified for the systems on which they would be used.
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Okay - soz then

So - next question - given all the different formats of cameras and their film/sensor sizes, why do you think everything should be 'scaled' to 35mm???

Why not to 6x6cm, 6x4.5cm, 6x7cm, cropped 1.5x or 1.6x or for the mini compacts, how about 5x4" or larger???

If you've never used a 35mm film camera, and just bought your first camera as a cropped sensor DSLR scaling anything to another format's field of view would be meaningless

And what about people who use both a D3 and D300??? Their lenses for the D3 would have the 'wrong' focal lengths on them every time they stuck them on the D300. Or a 6x6cm camera with the occasional 35mm film back - same problem, same lens is now 'wrongly' labelled

The makers chose to tell you what focal length their lenses are without reference to any cameras, that makes perfect sense to me

DD
 
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