EF, EFS, 1.6 sensor..... Technical question confusion.

Robbo

Robbo

Messages
3,962
Edit My Images
Yes
Just read some reviews on 17-50mm lens'

One was an ef fitting the other efs, both widest at 17mm.

The article said the ef fitting was wider than the efs fitting even though the same 17mm.

Is this due to the fact one is specifically designed for a crop sensor and the other can be used on full frame or crop? If that makes sense lol

Which lead me to this question...macro lens efs would display 1:1... But a macro ef lens would be 1:1 plus the crop factor as it's made to give 1:1 on full frame while the efs is specific for crop.

Anything making sense? Lol
 
Robbo said:
Which lead me to this question...macro lens efs would display 1:1... But a macro ef lens would be 1:1 plus the crop factor as it's made to give 1:1 on full frame while the efs is specific for crop.

Anything making sense? Lol
Click to expand...
Nope.....

1:1 is a ratio and nothing to do with crop factors. Lifesize is lifesize, a bigger sensor will just show more of the subject or be capable of framing a larger subject.

Bob
 
Canon Bob said:
Nope.....

1:1 is a ratio and nothing to do with crop factors. Lifesize is lifesize, a bigger sensor will just show more of the subject or be capable of framing a larger subject.

Bob
Click to expand...

Maybe I haven't explained very well... Try again.

As an efs lens is only made to fit a 1.6 body, the macro will be designed to give 1:1 on the 1.6 body.

An ef lens can fit full frame bodies to give 1:1, so on a 1.6 body will this give slightly more than 1:1 due to the crop factor?

Going of the review saying that 17 on ef fitting is wider than 17mm on an efs fitting
 
Last edited:
Robbo said:
Maybe I haven't explained very well... Try again.

As an efs lens is only made to fit a 1.6 body, the macro will be designed to give 1:1 on the 1.6 body.

An ef lens can fit full frame bodies to give 1:1, so on a 1.6 body will this give slightly more than 1:1 due to the crop factor?
Click to expand...

Don't think so? I would have thought that the only difference would be focus distance ..,.
 
Robbo said:
Maybe I haven't explained very well... Try again.

As an efs lens is only made to fit a 1.6 body, the macro will be designed to give 1:1 on the 1.6 body.

An ef lens can fit full frame bodies to give 1:1, so on a 1.6 body will this give slightly more than 1:1 due to the crop factor?
Click to expand...
No.

It helps get your head around it if you draw the light rays out on a piece of paper. The lens makes an image at the focal plane. The sensor sits at the focal plane and takes a rectangular area out of it. An APS-C sensor takes a smaller rectangular area than a full frame sensor. An object that fills the full frame area would be cropped (you'd only get a portion of it) on an APS-C sensor.

The reason the two lenses are different is that they aren't exactly 17mm at the wide end. The one that shows more is slightly shorter than the other.

The 1:1 business is a red herring. What that ratio tells you is how big the lens is capable of reproducing an image on the sensor. That is a 1:1 lens will be able to display a 5mm wide object at 5mm on the focal plane if you get it at the right distance from the lens (i.e. at the minimum focal distance). You'll notice that as the minimum focal distance goes up, so the projected image size decreases. Really, a macro can be thought of as a lens that will focus very close.

HTH
 
Robbo said:
An ef lens can fit full frame bodies to give 1:1, so on a 1.6 body will this give slightly more than 1:1 due to the crop factor?
Click to expand...

Nope again.....1:1 is a ratio. The crop factor will just show a smaller part of the subject, it doesn't magnify it anymore or less than a FF sensor.
Crop means exactly that....the framed subject is cropped, not magnified.

Lenses don't magnify more on a cropped sensor, you just see less of the subject/view

Bob
 
Last edited:
Canon Bob said:
Nope again.....1:1 is a ratio. The crop factor will just show a smaller part of the subject, it doesn't magnify it anymore or less than a FF sensor.
Crop means exactly that....the framed subject is cropped, not magnified.

Lenses don't magnify more on a cropped sensor, you just see less of the subject/view

Bob
Click to expand...

I see what our saying, but lol.... Bare with me ......

So, say the 5d is full frame with 12.8 mp vs my 50d at 15.1mp. At full size my image would be slightly bigger.

Meaning for the full frame image of the 5d to show the same as my 50d 1.6 sensor, it would have to crop in yea? Giving it a lot smaller mp again.

So when you say cropped sensor, it's not really cropping the image and zooming in as it displays a bigger part of the original images but still at full mp, not at a cropped version of the original.

Does that make sense? Am not good at explaining what I mean lol
 
Robbo said:
So, say the 5d is full frame with 12.8 mp vs my 50d at 15.1mp. At full size my image would be slightly bigger.

Meaning for the full frame image of the 5d to show the same as my 50d 1.6 sensor, it would have to crop in yea? Giving it a lot smaller mp again.

So when you say cropped sensor, it's not really cropping the image and zooming in as it displays a bigger part of the original images but still at full mp, not at a cropped version of the original.

Does that make sense? Am not good at explaining what I mean lol
Click to expand...
Forget about sensor sizes for a second. A lens creates an image at the image plane. The size of that image is totally dependent upon the focal length of the lens. If you held a piece of paper at the focal plane, you would get an image projected on it - much like a pinhole camera does.

All the sensors do is sample that image. An APS-C sized sensor will cover less of that image than a full frame sensor so you get less of it in the image. This is what the crop refers to. You are cropping the full frame image, just as you would in photoshop. The 1.6 factor comes in because to get the equivalent framing on a full frame sensor, you need a lens that is 1.6x as long.
 
1:1 just means that something is produced life size on the sensor regardless of how many pixels or focal length of the lens as Bob Say's. Take a picture of a ruler at 1:1 with different size sensors and you will see a image thats the same size as the sensor in the camera.

If you take a picture of a ruler at 1:1 with a full frame camera you will see 36MM across the frame then stick the same lens on a APS you would see 24mm, then same lens on a 4/3rd and you would only see 18mm.


formats.gif
 
Last edited:
I think you are mixing up different things. You are confusing focal lengths, sensor sizes, pixel counts and magnification factors.

I won't add more confusion by trying to explain any more, but if you have got your head around the various answers above, I think you should start again with a new question - one thing at a time!
 
Richard, I think I have baffled my self my tryig to mix things together that jaytdont go as you say. Lol, what a brain fart ey!

I already new about the focal length sensor sizes etc, I've just totally messed my head up mixing things that don't go together!

LAST TIME I EAT THEM ROUNDTREES RANDOMS!
 
Last edited:
Robbo said:
Richard, I think I have baffled my self my tryig to mix things together that jaytdont go as you say. Lol, what a brain fart ey!
Click to expand...

I think we're all just a little thankful that you didn't mention Dpi in the original question ;)

Bob
 
You must log in or register to reply here.
Back
Top