havent seen this question asked

okay i have a 20d

with a 75-300 mm

which i guess makes the lense really a 480mm

300 x 1.6 = 480

what does that equate to in the terms of focal mag

5X? 10X?

9.6x, if you believe a crop sensor actually magnifies the image.

the same x factor as before u added in the 1.6 crop FOV
cause it changes the short end as well..so its the same either way
and isnt it a 4x mag

Yeah it's a 4x .. 300/75 = 4

how do you figure it out am i wrong about the focal length with the sensor crop?

if thats true how do you do a prime lense?

the 75-300 on the 1.6 is 120-480
480/120 still 4x
a prime would be a 1x
and the 1.6 is not a magnification
its a cropped field of view to fill the frame as if it where 480mm but its still 300mm lens unless u add a teleconvertor on it

i didnt say it magnifies it ... did i?

but wait if a prime is ex:50mm is 1x then 500mm isnt a 1x is it.........

yes it is

your qustion has been ask tons of times. click link below

http://www.the-digital-picture.com …-of-View-Crop-Factor.aspx

On a point and shoot the "x" refers to how many 'times' stronger the long end is compared to the short end. It is all relative to the short end of the zoom you are referring to. In other words, all 3x zooms are not the same focal lengths. They could be, but they don't have to be.

Divide the long end of the focal length of a dslr zoom by the short end of the focal length and you have your "x" number.

So, a 75-300 is a 4x zoom.... and a 100-400 is also a 4x zoom.

Any prime can only be a 1x because it's not a zoom at all.

So if you are trying to compare the "x" number of a p&s to the focal length on a dslr lens you have to do the math or you're comparing apples to oranges.

The x doesn't mean anything to do with the power of the lens it's just longest focal lengh divided by the shortest focal lengh it's more of a buzzword for cheaper digicams because it sounds impressive.

The crop like people say doesn't make the lens longer but the effect is the same as having a longer lens as far as im concerend because it's an optical crop, and most lenses are more than capable of delivering enough resoloution through the smaller circle of glass used by a crop sensor.

A lot of inexperienced people read discussions on it and relate it to cropping on a computer but it isn't the same, on a computer the image becomes smaller and loses information.

People make the point that you can crop a full frame shot and get the exact same field of view but that is a destructive alteration to the image where as the crop sensor will have used all of it's pixels for that same field of view.

So while it is true that the lens isn't any longer you could perhaps say that the smaller sensor is making more use of it's resolving power.

If you had a crop sensor and a full frame sensor both of 8 megapixels and wanted to get as much of the subject recorded as you could with one lens it would make sense to use the crop sensor because if you cropped the full frame image to the same FOV it would have a significantly lower resoloution.

I suppose it's an advantage but only comapred to a full frame camera that has a lower resoloution once it has been cropped to the same FOV.

It's never been much of an issue to me, I only have 350d and not a full frame body and I just put lenses on it and take pictures.

Well said!

The magnification factor and the Zoom factor are two separate issues. Look at binoculars and telescopes, they magnify but don't zoom. Their listed magnification is based on using a 50mm focal length as the equivalent of the human eye. So binoculars advertised as 10x magnification have focal length of 500mm. Magnification factors are not used in photography advertising, probably because it's not as flattering or misleading as zoom numbers.

The 300mm lens on a 1.6 crop body gives about 10x magnification measured the same way binoculars are measured.


Ignore those who say the crop bodies aren't really 'full frame' ,that's a trivial argument

thats more of what i was asking^^^^^