EF lens on crop frame camera......

Ok, I have exhausted my search engine and cannot find the answer to my question (I had it once but forgot).

So hear is my issue: If I have a theoretical 18mm EF-S lens mounted on my crop frame camera what value EF type lens would I need to get the same frame?

Is it 18mm (EF-S) * 1.6 = 28.8mm EF series lens to equal that of the 18mm EF-S series lens on a crop frame camera?

ndekens wrote in post #13646192
Is it 18mm (EF-S) * 1.6 = 28.8mm EF series lens to equal that of the 18mm EF-S series lens on a crop frame camera?

No.

Forget about the "crop" factor. An 18mm lens is an 18mm lens. It does not matter if it's an EF or EF-S lens, 18mm is still 18mm.

The "perspective" will change depending if it's placed in an APS-C, APS-H, or FF camera but no matter what if you put an 18mm EF lens on a crop body you will get the same exact perspective as if you put an 18mm EF-S lens on th same body

Now if you want the same perspective in a FF body that the 18mm lens give you on a crop body then that is when you do the 18 x 1.6 to see what focal length you'll want.

But remember its is not the lens that changes the perspective(angle of view or what ever you way to call it) it is the body, so XXmm is still XXmm no matter if it's EF or EF-S

gremlin75 wrote in post #13646233
No.

Forget about the "crop" factor. An 18mm lens is an 18mm lens. It does not matter if it's an EF or EF-S lens, 18mm is still 18mm.

The "perspective" will change depending if it's placed in an APS-C, APS-H, or FF camera but no matter what if you put an 18mm EF lens on a crop body you will get the same exact perspective as if you put an 18mm EF-S lens on th same body

Now if you want the same perspective FF body that the 18mm lens give you on a crop body then that is when you do the 18 x 1.6 to see what focal length you'll want.

But remember its is not the lens that changes the perspective it is the body, so XXmm is still XXmm no matter if it's EF or EF-S

Thanks! I had it backwards!

gremlin75 wrote in post #13646233
No.

Forget about the "crop" factor. An 18mm lens is an 18mm lens. It does not matter if it's an EF or EF-S lens, 18mm is still 18mm.

The "Field of View" will change depending if it's placed in an APS-C, APS-H, or FF camera but no matter what if you put an 18mm EF lens on a crop body you will get the same exact perspective as if you put an 18mm EF-S lens on the same body

Now if you want the same FOV in a FF body that the 18mm lens give you on a crop body then that is when you do the 18 x 1.6 to see what focal length you'll want.

But remember its is not the lens that changes the FOV (angle of view or what ever you way to call it) it is the body, so XXmm is still XXmm no matter if it's EF or EF-S

You almost had it right.. I changed a few words.
Perspective is not a determined by the lens or body, it is determined by placement (camera relative to subject and background).

And to the OP.. Yes, you would need a 28.8mm lens on a FF to get the same frame (or Field of View) as you get on a crop with an 18mm lens (it is not a so-called 18mm, it is 18mm).

The EF-S lenses differ from EF lenses in that they are made to take advantage of space inside the body of an APS-C camera that is normally reserved for the path of the somewhat larger FF mirror as it swings. If the EF-S lenses were not made to prevent their being mounted on FF bodies, you would have a nasty collision inside the FF body when using an EF-S lens as it protrudes further inside of the camera body than a standard EF lens. Canon engineers use that space because it makes wide angle EF-S lenses less expensive to make.

18mm EF-S=18mm EF...

50mm prime on FF camera is 50mm Field of View and 50mm focal length.
50mm prime on 1.6 smaller sensor camera is 80mm Field of view and 50mm focal length.

It means with same lens on crop camera you will see the same object as on full frame camera, but small part of it.

To see the object at crop camera (EF-S mount) as it will be on Full Frame camera you need to step back. This will change the Perspective.

That's right, perspective is all a matter of camera placement versus subject. To prove this to yourself, you can try this fun exercise with a zoom lens (or a couple of primes)

1. Find a subject, say a fire hydrant or a willing model. Set your lens to say 50mm, walk until the subject fills the frame, take a picture.
2. Now, without moving from your current spot, (no moving around the model either), change to 17mm and take the same picture. Obviously the subject will not fill the frame any more, but that's ok.
3. Go home and download the pictures. Take the 17mm shot and crop it (or just zoom in) so that the subject fills the frame, just like the 50mm shot. Now compare the shots side by side, the perspective of the subject should be EXACTLY the same in both pictures and aside, from being blurry from zooming in, the images will look practically identical. (Let's not get into DoF calculations here.)

This is what a crop camera is doing in essence, it is cropping out a fraction of the full picture that a full frame camera would have seen. So the perspective of a 28mm lens on a FF and the perspective of a 28mm lens on the crop camera is identical IF the camera to subject distance does not change.

So what's the simple thing to do? Forget focal lengths, start by thinking what perspective will make this shot the most interesting? Make the subject look really big relative to the background? Or have a more pleasing compressed look for a portrait? Once you've decided this, it governs how far away you should stand away from the subject. Then and only then, choose a lens with a focal length to fill as much of the frame as you desire.

Zoom is no compensation for feet zoom.

hairy_moth wrote in post #13646268
You almost had it right.. I changed a few words.
Perspective is not a determined by the lens or body, it is determined by placement (camera relative to subject and background).

Meh, tomato-tomato (ok that phrase doesn't really work unless actually saying it) I knew what I meant (not that that helps anyone else, lol) and I'd rather be shooting then worry about correct terminology

But still thank you for the correction. In my mind they meant the same thing but I get the physical different between their meaning so I'll try to keep the correct terminology in mind next time

kf095 wrote in post #13646376
50mm prime on FF camera is 50mm Field of View and 50mm focal length.
50mm prime on 1.6 smaller sensor camera is 80mm Field of view and 50mm focal length.

The physicist in me has to rebel at this. How can the Field of View be measured in mm? Do you mean that an object 50 mm across would fill the frame when using a 50 mm lens on a full-frame camera, independent of its distance? Of course not.

Field of View should be measured as either an angle or the literal lateral extent of the field of view at a given distance (this is often quoted on binoculars).

What you really mean to say is that a 50 mm prime on a crop camera will produce an image with a field of view equivalent to the image produced by an 80 mm prime on a full-frame camera.

This may seem like just semantics again, but your phrase "50mm prime on 1.6 smaller sensor camera is 80mm Field of view" is, of itself, meaningless without your preceding phrase that makes it clear you have chosen a full-frame camera as a reference. As many people have said in many other threads in this forum, for most users it is only useful to compare with a full-frame camera if they have both a full-frame and a crop camera, or have used full-frame cameras extensively in the past. For someone who has only a crop camera, it is far more useful to compare the Field of View of different lenses on the same camera, rather than on a camera they might never own - that it the photographic decision most frequently encountered.

I'm sure you know this, as do most people on this forum, but it seems to me that newbies are confused enough by this constant distinction between crop and full-frame cameras without confusing terminology to add to it.

JHutter wrote in post #13647103
The physicist in me has to rebel at this. How can the Field of View be measured in mm? Do you mean that an object 50 mm across would fill the frame when using a 50 mm lens on a full-frame camera, independent of its distance? Of course not.

Field of View should be measured as either an angle or the literal lateral extent of the field of view at a given distance (this is often quoted on binoculars).

What you really mean to say is that a 50 mm prime on a crop camera will produce an image with a field of view equivalent to the image produced by an 80 mm prime on a full-frame camera.

This may seem like just semantics again, but your phrase "50mm prime on 1.6 smaller sensor camera is 80mm Field of view" is, of itself, meaningless without your preceding phrase that makes it clear you have chosen a full-frame camera as a reference. As many people have said in many other threads in this forum, for most users it is only useful to compare with a full-frame camera if they have both a full-frame and a crop camera, or have used full-frame cameras extensively in the past. For someone who has only a crop camera, it is far more useful to compare the Field of View of different lenses on the same camera, rather than on a camera they might never own - that it the photographic decision most frequently encountered.

I'm sure you know this, as do most people on this forum, but it seems to me that newbies are confused enough by this constant distinction between crop and full-frame cameras without confusing terminology to add to it.

I'm so sure kf095 appreciate you setting him straight. He'll learn from ya for sure. lol

Cheers,

David

This forum is chalk-full of pedants!

ndekens wrote in post #13646192
Ok, I have exhausted my search engine and cannot find the answer to my question (I had it once but forgot).

So hear is my issue: If I have a theoretical 18mm EF-S lens mounted on my crop frame camera what value EF type lens would I need to get the same frame?

Is it 18mm (EF-S) * 1.6 = 28.8mm EF series lens to equal that of the 18mm EF-S series lens on a crop frame camera?

Absolutely no difference, at all, between what you'll get with an EF lens vs an EF-S lens when mounted to your body. 18mm EF and 18mm EF-S are identical as far as what you would get.

"Crop Factor", as you've seen from all the other posts is confusing and (mostly) useless...and is only good for comparing two, different bodies with different sized sensors.

Here we go again ...

The short answer to OP's question is that: you got it right. End of story.

But people want to make things complicated and confusing .. sigh .. maybe that's the way of life (on these forums).

howiewu wrote in post #13647167
Here we go again ...

The short answer to OP's question is that: you got it right. End of story.

But people want to make things complicated and confusing .. sigh .. maybe that's the way of life (on these forums).

Unfortunately I must agree.

Now, depth of field and aperture will be a big factor, but that wasn't in the question.

I am assuming that the OP intends (and a lot of people missed this, apparently) that the EF-S lens on a crop camera is being compared to an EF lens on a *full-frame* camera: If the EF lens is used on a crop camera, the field of view will be the same. This is part of the reason why EF-S is such a draw: For the same angle of view, the focal length may be smaller, which results in a savings in the front glass element.

One of the draws of EF-S is that you can use a shorter focal length to get the same angle of view.

Bob Atkins explains it beautifully here (as always):
http://www.bobatkins.c​om …4&topic=124.msg​467#msg467

davidc502 wrote in post #13647130
I'm so sure kf095 appreciate you setting him straight. He'll learn from ya for sure. lol

I'm sure we're all very appreciative of your content-free snark, there. Next time leave it in the bus, eh?

The guy had an excellent point - and kf095's post is confusing precisely because he doesn't make clear that there is a different unit required to make sense of it. It is impossible to write understandably about EF versus EF-S without raising the issue of angular view.

1Tanker wrote in post #13647146
This forum is chalk-full of pedants!

My sentiments exactly! Pedant isn't a word I use normally, so I wikipedia'd it

Cheers,

David