EF/EFS Question
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Focal length doesn't change, but the field of view does
So an EF 17-40 has a FOV on a crop sensor of approximately 25-60mm and is no longer the wide angle it would be on a FF camera
Same goes for an EF-S lens too, but the lens is specifically made to work more efficiently on the smaller sensor
So an EF 17-40 has a FOV on a crop sensor of approximately 25-60mm and is no longer the wide angle it would be on a FF camera
Same goes for an EF-S lens too, but the lens is specifically made to work more efficiently on the smaller sensor
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Why? The focal length of a lens is just that, its focal length. If you put the same lens on a medium format camera, you'd still have the same focal length. What would change is the field of view. That's all, nothing more, nothing less.
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yes, but in usage, you're effectively getting a longer focal length. If my old bridge camera had the focal length stated in actual terms, it would be 6-60mm.
Since an EF-s lens can never actually be used with it's actual focal lengths, why list them and not the 35mm equivalents?
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No, you are getting a change in field of view - you are not getting an effective change in focal length. Depth of field and f stop stay the same, just you are seeing less of the scene. A 35mm EF lens will produce the same picture as a 35mm EF-s lens on an APS-C sensor. Imagine if you had to know which lens type it was before you could figure out whether it overlapped with what you already had.
?? You are using them at their focal lengths. You're mixing up photo composition (I have to stand in a different position/use a longer or shorter lens to take that photo) with lens characteristics (focal length, aperture).
woodbutcher
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Try it this way :-
I have an EF-S 18-55 kit lens. I like the images I get at 50mm but it is not fast enough for the low light I need. Do I
a) get the EF 50mm f 1.4 prime? or
b) assume that 50mm equates to roughly 35mm on a full frame and get an EF 35mm f1.4 L?
The same arguement the other way around would be :-
I have an EF-S (newly renamed to reflect it's FOV on a crop sensor) 11-35 kit lens. I like the images I get at 35mm but it is not fast enough for the low light I need. Do I
a) get the EF 35mm f1.4 prime? or
b) know the EF-S 11-35mm is psudeo-named by canon to reflect the FOV of my crop and it is the same as a 50mm on a full frame and get the EF 50mm f1.4?
Doing b) in either of the above will not give me what I was hoping for on my crop camera.
As said before, the focal length is just that. The Field Of View changes dependant on the body.
It is only when you change up to full frame (or down to crop) that the focal lengths (for composition) you thought you knew all become slightly different and you have to rethink your favourites.
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No, the APS-C one would look more zoomed in because of the crop factor. The DoF would be the same, but you wouldn't be able to fit as much into the frame as you would on full frame bodies, because of the crop factor.
What i mean by 'actual' is that a 18-55mm EF-s will never be able to frame the same area that an 18mm lens can on full frame.
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woodbutcher
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Both lenses fit on the APS-C camera and on THAT camera they BOTH produce the same picture.
If they were to both work on full frame, again they would both produce the same picture.
EF-S dictates that the lens is designed to fit and work on an APS-C camera.
EF fortunately works on both giving APS-C users a greater choice of lenses.
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Ah, sorry, I though he said on APS-C and full frame (not both on APS-C)
The difference is though that the EF-s one could never be used as a 35mm lens on a full frame camera. So the EF-s 35mm could never be actually used to give a 35mm effective focal length (I know the actual focal length is the same, but the EF-s could only ever be used as a 56mm equivalent.
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But the 35mm lens on a FF camera won't produce the same "effective focal length" as a 35mm lens on a medium format camera. Why should 35mm EFL be "the reference". Actually, it does provide the same FL, just the field of view will be different... Once you separate focal length from field of view (which is what frames the picture) it becomes obvious
woodbutcher
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Ok, poor example, numbers completely random to illustrate a point.
I have 3 cars and 1 engine. My engine is 3.5 litres.
I put said engine in car 1, a reliant robin and find if I am brave (stupid) enough, I get 0-60 in 4 seconds.
I swap the engine into car 2, say a ford focus. My 0-60 time increases to 7 seconds.
If I put it in a transit van, the 0-60 time again increases to 10 seconds.
What you are effectively asking me to do is call my engine different sizes because it produces different results dependent on which car I put it in.
Which car do I use as my standard? The ford focus? I call my engine 3.5l so it acts like a 4.2l in my robin and only a 2.8l in my van?
In reality the engine size is 3.5 litres and physically won't change no matter which car I choose to use. I just need to know what to expect from it when I switch cars.
I have 3 cars and 1 engine. My engine is 3.5 litres.
I put said engine in car 1, a reliant robin and find if I am brave (stupid) enough, I get 0-60 in 4 seconds.
I swap the engine into car 2, say a ford focus. My 0-60 time increases to 7 seconds.
If I put it in a transit van, the 0-60 time again increases to 10 seconds.
What you are effectively asking me to do is call my engine different sizes because it produces different results dependent on which car I put it in.
Which car do I use as my standard? The ford focus? I call my engine 3.5l so it acts like a 4.2l in my robin and only a 2.8l in my van?
In reality the engine size is 3.5 litres and physically won't change no matter which car I choose to use. I just need to know what to expect from it when I switch cars.
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But the 35mm lens on a FF camera won't produce the same "effective focal length" as a 35mm lens on a medium format camera. Why should 35mm EFL be "the reference". Actually, it does provide the same FL, just the field of view will be different... Once you separate focal length from field of view (which is what frames the picture) it becomes obvious
It suppose it would complicate things more to name the lenses in 35mm eqiuv focal lengths. It's just that, in practice (disregarding DoF for a minute), focal length and field of view sort of mean the same thing (I know they DON'T mean the same thing, but when you're framing a picture, they might as well be)
I've noticed panasonic do it with their micro 4/3rd lenses in their catalogue. They list a lens as a 90-400mm, which is actually a 45-200mm, but since it's m4/3 it is only ever going to be used as an effective 90-400. But with a brand that has 35mm and APS-C, I suppose it would be more complicated to do this.
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Not really, the lens itself is marked as a 45-200mm and generally only listed for sale as a 45-200mm as with all the other lenses:
http://www.four-thirds.org/en/microft/lens.html
For a while Olympus were badging their lenses with both the actual focal length and the equivalent focal length with different colours to make the difference clear but I don't think they've continued that with micro 4/3.
John