EF vs. EF-s

[arodrigz]

Hi all, just picked up a new T3i and thinking about lenses. As I understand it, if I put and EF lens on a T3i I have to multiply the mm of lens by 1.6 because of the cropped sensor. Is this also necessary for the EF-s lenses?

So my kit came with the an 18-55 and 55-250. Are these as stated or is the 18-55 actually a 28-88 and the 55-250 an 88-400?

Thanks
Alex

 

[GeorgieGirl]

An EF-S lens will only fit the type of sensor/body you have. It will not fit a Full Frame Canon for example. BUT, all EF lenses will fit both sensor types are are interchangable. The mm of the lenses do not change, its the apparent change you have noted that is the resold of that 'mm' on a crop body...Crops 'magnify' the subject more in an affort to make it as conceptually simple as possible. Probably as sloppy analogy, but one I like.

 

[Overread]

The focal length always remains the same no matter if the lens is EF or EFS. A 50mm EF lens and 50mm EFS lens on your camera will give you exactlty the same image.


The difference is that the EFS lens won't fit onto a fullframe camera body, whilst the EF lens will. Furthermore the fullframe bodies have a larger sensor than the crop sensor ones, this results in the angle of view (what you see) being tighter (appearing more magnificed) on crop sensor compared to fullframe.
This is where the multiply by 1.6 comes from - in comparing the same focal lengths, on a lens, between the different sensor sizes.

In general if you've no experience of fullframe/35mm film size cameras then the conversion is meaningless since you're not trying to compared to an angle of view you used/saw on those bodies.

If you have experience of those bodies then, to get the same angles of view you will have to convert the numbers - with your maths being correct, the 18-55mm, for example, giving you similar angles of view on the crop sensor body as would a 28-88mm lens on a fullframe/35m body.

 

[arodrigz]

Ok, so the aps-c sensors will magnify whatever lens I choose to put on there be it EF or Ef-S?

 

[Overread]

It won't magnify the image so much as record a smaller part of it. The sensor is smaller so it records a smaller part of the middle of what the lens creates, this results in the image appearing more magnified than if the same scene is used with a camera on a larger sensor (which captures the edge details).

EF lenses create an image large enough for the fullframe sensors - the crop cameras just miss out the edge light; whilst EFS lenses are made to only make the middle part of the image (thus letting them be smaller and lighter) and don't create the outer edges (which the crop camera wouldn't see anyway even if they are there).

EFS won't fit onto fullframe/35mm bodies; but if you can fix them then you' get a big black boarder around the picture as a result of the smaller image circle.

 

[arodrigz]

Oh thanks, that was helpful. I'm a newbie to photography so I won't concern myself with 35mm equivalents

 

[arodrigz]

It won't magnify the image so much as record a smaller part of it. The sensor is smaller so it records a smaller part of the middle of what the lens creates, this results in the image appearing more magnified than if the same scene is used with a camera on a larger sensor (which captures the edge details).

EF lenses create an image large enough for the fullframe sensors - the crop cameras just miss out the edge light; whilst EFS lenses are made to only make the middle part of the image (thus letting them be smaller and lighter) and don't create the outer edges (which the crop camera wouldn't see anyway even if they are there).

EFS won't fit onto fullframe/35mm bodies; but if you can fix them then you' get a big black boarder around the picture as a result of the smaller image circle.

Hence why they won't work on the full frame camera! I get it, Thanks

 

[Overread]

Yep, though there is also a more physical reason; with canon own brand EFS lenses the rear of the lens pushes into the lens mount; on a fullframe body this is far enough that it will hit the mirror as it flicks up, which results in all kinds of problems. Some of these lenses can be modified to fit (youtube has some examples I think) though generally its not always worth it.

Also 3rd parties that make crop sensor specific lenses only use the EF mount not the EFS mount, so they will fit to fullframe bodies; but its hit or miss with these as to if they recess enough to hit the mirror (something to research on before trying).

 

[DennyCrane]

As to the crop factor, picture 2 identical circles representing the image through a lens. In the first circle, imagine a rectangle large enough so it's 4 corners touch the diameter of the circle. Imagine that as a full-frame camera sensor. Now imagine a rectangle 60% of the size full frame sensor, centered in the circle. You're not magnifying anything with your sensor and an EF lens, it's just that 2 identical pictures, one taken with each camera, the crop sensor camera will be of a smaller area. And, when formatted into the same size picture, will seem to be magnified.

 

[arodrigz]

As to the crop factor, picture 2 identical circles representing the image through a lens. In the first circle, imagine a rectangle large enough so it's 4 corners touch the diameter of the circle. Imagine that as a full-frame camera sensor. Now imagine a rectangle 60% of the size full frame sensor, centered in the circle. You're not magnifying anything with your sensor and an EF lens, it's just that 2 identical pictures, one taken with each camera, the crop sensor camera will be of a smaller area. And, when formatted into the same size picture, will seem to be magnified.

So, using the rectangle example, if I wanted the same size picture that was identical with both cameras, I would have to manually (software) crop the cropped censor picture and magnify that portion of the picture that I wanted to match with the picture the full frame camera produced which also would mean that the full-frame censor would always produce a sharper picture of its identical counterpart taken with a cropped censor?

 

[DennyCrane]

No, the crop sensor is smaller and captures a smaller percentage of the images through the lens.

 

[GeorgieGirl]

Generally a Full Frame sensor will produce a clearer image.

 

[Robin Usagani]

this discussion again!

 

[GeorgieGirl]

Settle down Robin....No not again for a fight, this guy is trying to learn something....


OP take a look at this link. I think the tests and photos used to illustrate will help crystallize some important details for you. I found it very informative, I hope you do too.

The Full-Frame Advantage

 

[arodrigz]

Settle down Robin....No not again for a fight, this guy is trying to learn something....


OP take a look at this link. I think the tests and photos used to illustrate will help crystallize some important details for you. I found it very informative, I hope you do too.

The Full-Frame Advantage

Great article, thanks. That was pretty clear. Now I need to make up my mind what lenses to get