Originally posted by Jüri
So to answer the inquiry of original poster, full frame 50mm lens does not replace a 75mm APS-C lens one to one. When both are compared on a Pentax dSLR, the latter will give narrower prespective. .
I disagree with you on this after doing a small bitof research with my kit lens, I found it actually does the exact same thing when i put it on my old film camera, the only thing differently that it does is some vignetting, that of which is expected with a lens designed for APSC sensors(there is no need to make these lenses so that they are covering a larger sensor)
This is one of the reasons I like buying lenses designed for full frame cameras, ya they take a little bit of re figuring but they are fun to use and I can use them on my old cameras and maybe one day if the planets are lined up correctly they will come out with a full frame camera (I say that crossing my fingers)
In a nutshell I noticed that no matter which lenses I try out between my cameras they all have the same effect, on the old camera they seem zoomed out, and on the digital (smaller sensor)camera they are all zoomed in 1/3rd more.
I feel that the amount of light coming through the aperture is the same on either camera but their may be some differences in the depth of field from camera to camera but that will require some further research which I will submit my findings at a later date.
Yes I do believe in the "cropped" factor because for example~ say Hypothetically I have a full frame Pentax (I WISH) and put the 50mm lense on it then I get a larger image but at 50mm, then I take a shot with it on my K-x that has a 2/3rd size sensor compared with the full frame, and upload the identical images in to photoshop layers next to each other, you will see the "crop" example I am talking about, the smaller sensor image will basically look like it was just a crop out of the full frame image.
With digital imaging these days I am impressed at the difference between digital and film.
On the other hand you can also figure in the resolution factor, it makes sense to me that a 12 megapixel APSC sensor has the same resolution as an 18 megapixel full frame sensor, Resolution is respective to physical size of the sensors. So in closing I would say that an actual 2/3rds crop from an 18 MP full frame image would actually produce the same size image as if it was taken with a 12 MP APSC sensor.
Am I wrong here? Thoughts.......Anybody?