EF/EFs/cropfactor/fov brain explosion !!!

i have a question and i am really confused

im considering buying a new lens for me 400D (currently have efs 18-55) and i want something more telephoto than what i have.

today someone told me something along the lines of "yeee if u put on this ef 50mm 1.8 its basically a 85mm on ur 400d cause the sensor is smaller than a full frame"

ok so then i read all these forums and websites, and i'm pretty sure i understand that EF and EF-S lenses are marked with the same focal lengths, (EG 50mm ef lens is the same focal length as 50mm ef-s theres no phyisical diff in focal legnth)

but then ive read some places that say the field of view changes between the 2 types of lenses because the projected image from a EF an EFS onto the sensor are different sizes (hence a cropfactor)

SO does this mean my current EF-S lens set at 50mm will look different through the viewfinder and take diff photos than a EF 50mm (in terms of what is framed/field of view)????
thanks for reading

50mm on your kit lens and 50mm from the f/1.8 will give you the SAME view on your 400D.

solarcell wrote in post #6377779
but then ive read some places that say the field of view changes between the 2 types of lenses because the projected image from a EF an EFS onto the sensor are different sizes (hence a cropfactor)

The field of view only changes because the image is cropped when you you put the lens on a crop camera.

solarcell wrote in post #6377779
SO does this mean my current EF-S lens set at 50mm will look different through the viewfinder and take diff photos than a EF 50mm (in terms of what is framed/field of view)????
thanks for reading

No, nothing changes, both EF and EF-S lenses (at the same focal length) will have the same field of view when used on the same camera.

I think the misunderstanding is that in general, EF-S lenses are only used on crop camera and always have a narrower field of view when used on a crop camera.

Does that make any sense?

msowsun wrote in post #6377835
I think the misunderstanding is that in general, EF-S lenses are only used on crop camera and always have a narrower field of view when used on a crop camera.

Does that make any sense?

I fell into that misunderstanding too when I first started as I think a bunch do. I thought EF-S lenses compensated for the field of view on the crop but they don't. Same view as EF lenses at the same length. If you've never played with a full frame camera before like me, I don't think it's something to worry about solarcell.

EFS ONLY means that the mount and back of the lens is different than on EF lenses (thus is cheaper to manufacture), and only works on the 1.6 APS-C crop bodies (except the 10D) because the mirror is smaller and won't hit the back of the lens. It does not have anything to do with their focal lengths.

This knowledge, coupled with this post showing the FOV for different sensors, should clear things up.

https://photography-on-the.net …php?p=3436066&p​ostcount=9

msowsun wrote in post #6377835
The field of view only changes because the image is cropped when you you put the lens on a crop camera.

For Solarcell: The above can be misleading, as there's no reference to putting the same focal length lens on a so-called "full-frame" (35mm film or a 35mm film-sized sensor) camera.

This thread from the forum "stickies" would be a good place to start learning about the "crop factor".

As said above, if the only SLR you own and have any experience with is an APS-C format camera, you really can totally forget the "crop factor". The only reason you might do a calculation from time to time is, for example, if someone tells you that they used a XXXmm lens to make a particular shot using a 35mm film camera and you want to try to duplicate the shot from the same vantage point with a 40D.

Picture in your mind that you are looking out the front window of your house. The window represents, let's say, a large format view camera, a "graphic" with a certain lens. We are not going to change this lens, we are going to change the film size and or the sensor size. As you stand there, you can see a certain "picture" framed by the window.

Now, you do NOT change position, but your wife comes along and closes the drapes by some amount. That smaller view (field of view) now might represent say, the old roll film, you know, a "Brownie" 120 with smaller film than the first example

She decides the light is still bothering her, so she closes the drapes still further, and you, while still standing in the same spot, can now see even LESS (field of view).

That view might represent, say, a full frame DSLR, or 35mm film

Finally, she closes them JUST a little bit more, giving you even LESS to see, while you have remained in the same spot all this time.

This final, small view, might represent your crop DSLR.

Notice that what you can see in the frame HAS REMAINED UNCHANGED. That is, say you can see a small flowering bush in the center of the frame. When the curtains were opened, that flowering bush looked JUST THE SAME as it does now with the curtains nearly closed----it's just that you cannot see as much of the frame

440roadrunner wrote in post #6380199
Picture in your mind that you are looking out the front window of your house. The window represents, let's say, a large format view camera, a "graphic" with a certain lens. We are not going to change this lens, we are going to change the film size and or the sensor size. As you stand there, you can see a certain "picture" framed by the window.

Now, you do NOT change position, but your wife comes along and closes the drapes by some amount. That smaller view (field of view) now might represent say, the old roll film, you know, a "Brownie" 120 with smaller film than the first example

She decides the light is still bothering her, so she closes the drapes still further, and you, while still standing in the same spot, can now see even LESS (field of view).

That view might represent, say, a full frame DSLR, or 35mm film

Finally, she closes them JUST a little bit more, giving you even LESS to see, while you have remained in the same spot all this time.

This final, small view, might represent your crop DSLR.

Notice that what you can see in the frame HAS REMAINED UNCHANGED. That is, say you can see a small flowering bush in the center of the frame. When the curtains were opened, that flowering bush looked JUST THE SAME as it does now with the curtains nearly closed----it's just that you cannot see as much of the frame

I like this explanation, but am working an idea that would take it a bit further - such as projecting the image coming through the window on a wall on the opposite side of the room with some sort of lens. Think of putting the person inside the camera.....

hahahah ok firstly thanks for all the replies and effort u guys put into explaining, but im still not 100% certain

SO what i understand is that an ef and efs lens will give the same field of view same look same image... that has been stated well

and it has been well explained that given a certain lens and changing image sensor sizes the smaller sensor will simply give a cropped version of the bigger sensor (thanks to roadrunners analogy)

and the first few posts stated that given a 1,6crop sensor the captured image will be the same regardless of whether for eg the 50mm is ef or efs..... but are u sure ??
hahhah im sorry i just dont get it cause if the efs lens is projecting a smaller image circle than an ef lens then surely the image from the ef lens will crop out the parts of the image circle exterior to the sensor whereas the efs will focus the whole image onto the sensor...
i'm more confused about what happens to the image taken (ie is it cropped at all) when comparing an EF and EFS lens on the same sensor YES OR NO???
(i understand how changing the sensor size affects the image)

Bottom line, if you take any lens (EF or EFS) and stick it on your XTi and set them all at 50mm, as an example, you will see the same scene with all lenses. EFS was a way for Canon to manufacturer a cheaper lighter lens, and has nothing to do with the image, focal length, field of view, etc.

Dont get caught thinking you are getting more lens for your dollar.
Focal length of a lens does not change when placed on a cropped sensor.
In fact you are getting quite the opposite. ie less captured image on a crop sensor than you would on a full frame sensor

solarcell wrote in post #6383468
hahahah ok firstly thanks for all the replies and effort u guys put into explaining, but im still not 100% certain

SO what i understand is that an ef and efs lens will give the same field of view same look same image... that has been stated well

and it has been well explained that given a certain lens and changing image sensor sizes the smaller sensor will simply give a cropped version of the bigger sensor (thanks to roadrunners analogy)

and the first few posts stated that given a 1,6crop sensor the captured image will be the same regardless of whether for eg the 50mm is ef or efs..... but are u sure ??
hahhah im sorry i just dont get it cause if the efs lens is projecting a smaller image circle than an ef lens then surely the image from the ef lens will crop out the parts of the image circle exterior to the sensor whereas the efs will focus the whole image onto the sensor...
i'm more confused about what happens to the image taken (ie is it cropped at all) when comparing an EF and EFS lens on the same sensor YES OR NO???
(i understand how changing the sensor size affects the image)

Ok, you are right about the image circle thing. On an EF lens there is a large part of the image circle that is "wasted" and falls outside of the sensor. On the EF-S lens there is not any wasted image circle; it fits the sensor perfectly.

However, the focal length that they are giving is the same, because it is measured in an absolute sense. A 50mm lens has a focal length of 50mm; there is no changing it, you can look at it on a ruler (almost exactly 2 inches), you can't change 2 inches, it's just defined that way. If you look on a compact point-and-shoot camera (like a Digital ELPH) you will see that the lens is something like 3.5-10.2mm. This is once again a fixed measurement, and it gives normal-looking photos because the sensors on those cameras are tiny. A 50mm lens on a camera like that would be WAY zoomed in. Like cropping the middle 10% out of a DSLR shot with a 50mm lens.

So, yes, 50mm on an EF lens and 50mm on an EF-S lens look the same on an crop sensor camera. But 50mm on a full-frame camera looks way different from 50mm on a crop camera.

If you look at the "standard zoom lens" for 35mm film (aka full frame) for many years it was something like 35-80 or 28-90. It straddled 50mm because 50mm was approximately "normal" (same FOV as what human eyes see). Now because the sensor is smaller we have standard zoom lenses like 18-55mm. This translates to 29-88 mm, almost exactly the same as the good old 28-90. From wide to telephoto, but not very much on either side. If you look at other brands of DSLR's (say, Olympus) you will see that they have a different crop factor, so their standard zoom lenses are 14-42mm or something like that. All lenses are measured the same in terms of raw millimeters, but their "35mm equivalent field of view" is different depending on the crop factor.

So if you want to go "more telephoto" than your current 18-55 lens, you need a lens longer than 55mm, no matter if it is EF or EF-S. I would probably recommend the 55-250, as it is reasonably cheap, reasonably good quality, has image stabilization and quite a big telephoto range for your 400D.

solarcell wrote in post #6383468
hahhah im sorry i just dont get it cause if the efs lens is projecting a smaller image circle than an ef lens then surely the image from the ef lens will crop out the parts of the image circle exterior to the sensor whereas the efs will focus the whole image onto the sensor...
i'm more confused about what happens to the image taken (ie is it cropped at all) when comparing an EF and EFS lens on the same sensor YES OR NO???

Standard EF-mount lenses project an image circle large enough to cover a 35mm film frame (24mm x 36mm). They will project the same circle of light regardless of whether you mount them on an older 35mm film camera or on an APS-C camera such as a 40D.

If you mount a standard EF-mount lens on the 40D, the projected image circle is larger than the APS-C sized sensor in the 40D. Thus, the sensor merely ignores the portions of the image that do not fall on the sensor.

EF-S lenses (and the other manufacturer's "digital-only" lenses) project a smaller image circle that is large enough to cover the APS-C sized sensors that they were designed for. If you used one of these lenses (the third-party lenses or a modified EF-S lens) on a 35mm film camera, you would see a black circle around the image.

Now we'll get to what seems to confuse you....

Assume you are photographing a small automobile that is stationary and 30 feet away from you and you are using a 40D camera on a tripod. Using an APS-C lens adjusted to 28mm lens allows you to fill approximately one half of the image in your 40D. In other words, the automobile image fills 1/2 the length of the APS-C sensor in your 40D camera.

Now, get yourself really tiny (don't ask how to do this, but I've seen it done in the movies :rolleyes and get yourself inside the 40D camera. Now you can measure the length of the image of the automobile on the sensor. The image of the car would be roughly 11mm long inside the camera. There will be some elements of the image that fall onto parts of the camera that are beyond the edges of the sensor, but not too far away.

You've done this with an APS-C zoom lens adjusted to 28mm. Now, while you're still inside the camera, your full-sized assistant changes the lens to an EF-mount 28mm lens but does not change the aim of the camera. Again, take out your tiny measuring tape and measure the image of the automobile on the sensor. It will still be the same roughly 11mm long image on the sensor that you observed and measured while using the EF-S lens. You will notice, however, that there is more of the image falling on parts of the camera around the sensor. In other words, parts of the camera further from the sensor now have some image elements focused on them. The sensor cannot "see" these parts of the image, though, so what the camera produces as an image file won't have them included.

Now, your problem is getting large enough again to hold the camera.

Does this help explain it maybe? A quick sketch I made up to try to help, probably not 100% accurate, but it should serve to conceptualize what is going on.

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HA okokokok

i think i get it nowww

thanks guys for the patience and effort....
ive always despised the ability of mankind to make as many different formats as is humanly possible.