DSLR sensor crop factor question?

Question

canon EOS 400D (rebel XTi) has crop factor of 1.6x .
kit lens is 18-55mm.
my question: is 18-55mm the 35mm equivalent or (18-55)x1.6= 28.8-88mm the 35 mm equivalent.


Also for lenses in general, is the focal length given in specifications 35mm equivalent ?

the first question has 2 options. a simple yes didn't answer my question

Answer 1

If you can somehow fit the kit lens (18-55mm) on a full frame 35mm camera (Which is not possible for the EF-S lens), the focal length will be 18-55mm.

When you put the 18-55mm lens on your 400D. It will have the same effect as a 28-88mm lens fit on a full frame 35mm camera.

All Canon EF and EF-S lenses focal length are rated using 35mm standard.

Answer 2

The focal length is given in 35mm format. You have to do the math. Remember that the EOS system has been around since the mid-80's and any of the lenses and flashes from the older EOS cameras will work on your new Rebel XTi.
What is good about the 1.6 factor is it does not effect your aperature so that lens is a 3.5 to 5.6 all the way through.
Hope it helped!

Answer 3

Focal length has nothing to do with the film size or sensor size. It is a measurement of a physical property of the lens.

While they may advertise the lens in terms of the "35 mm equivalent," I have never seen a camera or lens that was actually labeled this way. This is why you see point and shoots such as my CoolPix 5400 saying "28-114 mm" on the box and "5.8-24 mm" on the lens. This is probably also the origin of the heavy role played by the "zoom factor" (such as "3X" or "4X") instead of using the actual focal lengths. In some ways, it reduces the confusion about the range of the lens.

Instead of using the "lens factor," some people now advocate refering to lenses in terms of the angle of view instead of focal length. This terminology would level the playing field and we would not need to use conversion factors to compare lenses to our familiar terminology. I kind of doubt that the "angle of view" camp will be successful, though, because people have been dealing in focal length measurements for so long. It would be similar to the days when "they" tried to convert the USA to using the metric system.

In other words, all of the previous answers are correct. 18-55 is the ACTUAL focal length of your lens. If you are putting it on an XTi, you would have to multiply by 1.6 to see what focal length it will mimic if you are comparing it to the 35 mm film world that we are accustomed to. If this was not true, why don't manufacturers provide multiple sets of focal lengths to correspond to various sensor sizes.

Consider the Canon line, for instance. They have 3 distinctly different sensor sizes. Each has its own focal length multiplier.

Camera > Sensor > Lens factor
30D > 22.5x15.0 > 1.6
XTi > 22.2x14.8 > 1.6
1D MkIIN > 28.8x19.1 > 1.3
5D > 36x24 > 1.0

If Canon makes EOS-EF lenses that will fit ALL of these cameras, why don't they tell us three different effective focal lengths? It would be bizarre to do so; that's why. They just tell us the true focal length and leave the math to the individual camera owner to apply as needed.

Answer 4

a common mistake, EF-S lenses still require the 1.6x FOV factor to match against 35mm equivelants. Thus 18-55 on a digital rebel is going to give you the same view as a 28-90 lens on a film rebel.

The EF-S lenses are more matched for a CMOS sensor (requiring 24mm coverage instead of 35mm) and are optimized for sending light straight back to the cmos chip rather then spreading it out in a flat film plane.

28mm on a digital camera that has a crop factor is no longer wide angle. 18mm is concidered wide for a 1.6x crop.

Answer 5

yup, it is 28x90. all lenses will need to apply the 1.6x to the specified focal lenth

Answer 6

Yes and yes, you are spot on.