Auerbach Loc: Chappaqua, New York

I shoot with a Canon 80D and a T6s. I have multiple EFS, EF AND L lenses and am aware of the focal length adjustment which needs to be made when shooting with an “EF or L” lense on an APC body. I was just looking at my EF-S 10 -18 zoom and wondering whether the lense was a true 10-18 or was it a 6.25 - 11.25 with an effective focal range of 10 -18?

RichardTaylor Loc: Sydney, Australia

It is a 10-18mm focal length lens. However the effective field of view (in 35mm( full frame) terms) is 16mm-28mm (the crop factor for your bodies is 1.6).

cthahn

What ever is marked on the lens is what it is. Depending on what camera you use will determine the effective value or how the picture will turn out.

ATCurry

In other words, you do the same calculation with all the lenses, even the EF-S lenses.

GoofyNewfie Loc: Kansas City

...and you don't have to do any calculations to use it.
Looking through the viewfinder shows you what you will be getting.

Auerbach Loc: Chappaqua, New York

Ok, got it. But why would Canon Mark a lense 10-18 when it can only be used on an APC camera and is really 16-28. Isn’t that false advertising

ATCurry

Because of the definition of what focal length is. From a Nikon site: "The focal length of the lens is the distance between the lens and the image sensor when the subject is in focus, usually stated in millimeters (e.g., 28 mm, 50 mm, or 100 mm). In the case of zoom lenses, both the minimum and maximum focal lengths are stated, for example 18–55 mm." It does not describe the size of the sensor. The concept of "equivalent" as a description relates different sized sensors, to a sensor sized the same as a 35mm film image--which was a common size when digital photography was introduced.

RichardTaylor Loc: Sydney, Australia

It really is a 10-18.

CHG_CANON Loc: the Windy City

The focal length is the focal length. period.

Peterff Loc: O'er The Hills and Far Away, in Themyscira.

It seems that you still do not understand. As regularly said in this thread, and many others, the focal length of a lens is the focal length of the lens regardless of the body or camera sensor size that it is mounted on. Your 10-18mm lens is a 10-18mm lens, just as my 8mm fisheye is an 8mm fisheye, or my 500mm telephoto lens is a 500mm telephoto lens regardless of the type of camera or sensor size that the lens is mounted on. There is no false advertising in this situation, on behalf on Canon or anybody else, just a false and mistaken sense of understanding.

Perhaps the simplest way of explaining this problem is that so many photographers (especially on UHH) learned their craft with 35mm film cameras, which of course always had the same size of sensor (35mm film), and built their mental reference model about "the effect" of different focal length lenses on that standard, which only translates 1:1 to digital with a full frame (35mm film size) sensor. It is the camera that has changed when using a different size sensor, not the lens, so the lens does the exact same things with light, but the camera sees that result differently.

Since both of your cameras are APS-C, I would forget all about the 1.6 conversion factor, or doing any math, and just use your lenses based upon the experience you see in the viewfinder, which has ~100% coverage on your 80D. You should soon get a good intuitive feel of what any lens will do on either of your bodies.

Don't let Mephistopheles tempt you into thinking differently, it won't make you a better photographer, nor give you unlimited knowledge, nor unlimited access to worldly pleasures!

GoofyNewfie Loc: Kansas City

It would be false advertising to mark it as a 16-28.

PGHphoto Loc: Pittsburgh, PA

I think the easiest (and over-simplified) way to think of it is focal length is a physical measurement of the hardware involved. It doesn't change regardless of what camera you put the lens on. The crop factor is exactly what it sounds like. If you compare the picture taken with a full frame sensor to a picture of the same subject at the same distance with the same lens on a crop sensor, it will look like you cropped the picture before printing/viewing it. So the 'field of view' with a crop sensor is smaller.

Some think of the crop sensor image as being magnified but realistically, its the same as cropping a full frame sensor shot . So a 1.6 crop factor on a 50 mm lens would give you what LOOKS LIKE a picture you would have gotten with an 80mm lens on a full size sensor. I say this is over-simplified because it doesn't get into the pixel density difference and other physical characteristics. The general idea is there though.

mwsilvers Loc: Central New Jersey

There is no adjustment you need to make when shooting with an EF or an L lens on an APS-C body. A 50mm L lens will give you results identical angle of view to a 50mm ef-s lens. All of your lenses whether they are EF-S, L or just EF all have the exact focal length that's marked on them. There is NO change to the focal length on any of them on an APS-C sensor. The apparent difference in angle of view between the image on a full frame camera or an aps-c camera is due to the sensor size alone. EF-s lenses are built with a smaller image circle for specific use with an aps-c sensor, otherwise there is no difference. The lens does not change depending on which camera it's being used. This is a mistake often made by newbies and others who are not so new but should know better.

mwsilvers Loc: Central New Jersey

It's still 10 -18mm regardless. Using it on a smaller aps-c sensor gives the impression that the focal length has changed, but it has not. Any lens used on an APS-C camera regardless of whether it's an EF-s EF or L will work exactly the same way. A 10-18mm lens on an APS-C body gives a 35 mm equivalent angle of view similar to a 16-29 mm lens on a full frame camera. The sensor size, not the lens is responsible for the apparent difference.

Auerbach Loc: Chappaqua, New York

Thank you all — and yes, I started shooting in 1965 with a Miranda Sensorex (which still works perfectly). So at times the 1.6 factor throws me.