50mm means 80mm in digital, what about 75-300?

I hope this is not a stupid question...

When canon sells the EF 75-300mm f/4-5.6 USM III, are they referring to the 35mm film standard by saying 75 300mm? What does this make this lens when you use it on a digital camera?

Prepare for the avalanche! This question always sets off a deluge.

In brief, the answer is if you are familiar with 35mm SLR photography, then multiplying focal lengths by 1.6 will give you an idea of the angular field to expect. If you've never been used to 35mm then you should ignore all this talk about multiplication factors.

The actual focal length doesn't change, only the angular field you get.

I found this confusing at first too.

All lenses are sold as per their actual focal length, i.e. a 50mm lens has a focal length of 50mm. But a 50mm lens on a "1.6 crop" camera (like a 400D, 30D, etc.) gives you the same field of view as a 80mm lens would on 35mm. Why? Because the sensor is 1.6 times smaller than 35mm film, and it therefore crops out part of the image that film would normally capture. So multiply by 1.6 to get numbers that make sense if you're used to film shooting.

Of course, a 50mm lens on a medium format camera would be like a wide-angle lens on 35mm It's all relative ...

Yes, to your first question.
The answer to the second depends on the camera body.
Generally you multiply by 1.6 to get the effect of the smaller sensor of the camera. Of
course this differs if you have a full frame sensor or if you have a 1.5.

Ok I understand it now. Thanks for both of you.

vash wrote in post #3435577
Yes, to your first question.
The answer to the second depends on the camera body.
Generally you multiply by 1.6 to get the effect of the smaller sensor of the camera. Of
course this differs if you have a full frame sensor or if you have a 1.5.

What about in the case of a rebel xt (350d)?

I have the following lenses:

50mm USM 1.8 II
75-300mm USM f4 III
28-90 USM

The Rebel XT is a 1.6 crop camera.

emre2006 wrote in post #3435586
What about in the case of a rebel xt (350d)?

I have the following lenses:

50mm USM 1.8 II
75-300mm USM f4 III
28-90 USM

As 350D is a 1.6 crop camera, this was answered by madweasel

Madweasel wrote in post #3435554
... multiplying focal lengths by 1.6 will give you an idea of the angular field to expect.

so your 50mm will have a field of view similar to an 80mm, your 75-300 will have a FoV similar to a 120-480mm, and the 28-90 will be like a 45-144

emre2006 wrote in post #3435546
When canon sells the EF 75-300mm f/4-5.6 USM III, are they referring to the 35mm film standard by saying 75 300mm?

vash wrote in post #3435577
Yes,...

No! Canon is refering to the focal length of the lens. Type of camera has nothing to do with it.

The focal length of a lens does not change on different camera bodies, but the field of view may.

Ok, please let me know if I understand this correctly then...

If you have a lens at 300m on a digital rebel xt, this means the lens is producing a 300mm FOV but the camera can only capture a smaller area of the bigger picture the lens is producing w(1/1.6=0.625) ,which is actually a CROP FROM the 300mm image. So you don't exactly have a 400 something mm lens but its just like taking a picture and cropping it with photosohop to its 0.625 size. ?

PS: I have quickly made an illustration of what I understood from the discussion, please tell me if its correct.

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Looks like you have it figured out. Here's some more info.

http://digital-photography-school.com/blog/crop-factor-explained/

http://www.cambridgein​colour.com …al-camera-sensor-size.htm

Thanks for the websites, they are very interesting...especial​ly this part:

mage information is never ideal, however it does have its advantages. Nearly all lenses are sharpest at their centers, while quality degrades progressively toward to the edges. This means that a cropped sensor effectively discards the lowest quality portions of the image, which is quite useful when using low quality lenses (as these typically have the worst edge quality).

Field of View is the measurement of what the camera sees and can record using a 35mm film or "fullsized" CMOS sensor a reference source. That being said, the CMOS sensors in these "crop" cameras use a sensor smaller than the size of a frame of 35mm film. So obviously, you will not be able to record the same FOV (field of view). It is like using a projector and displaying on a screen that's too small for the projected image, some of it gets cropped out.

Since these crop cameras use a sensor 60 % of the size of a 35mm film/full frame, the focal lengths are multiplied by 1.6 in order to get the accurate focal length equivalent.