Railfan Technology > Sensor Sizes

https://photographylife.com/what-is-crop-factor#more-42523

Although many are probably up on this, seems to be a reasonable review article on sensor sizes.
Interesting tho, emphasizes that a crop sensor does not change the focal length of a lens(ie magnification) but
then seems to muddy the water by talking about them having more "reach".

Bob Jordan

The "reach" is a bit of a misnomer but the feature can be useful. Think of it like cropping on an enlarger. You take a photo with your camera and lens but the subject is too far away and gets lost in the scenery. So you back the enlarger out and only print a smaller part of the negative so it looks like you were closer removing the distractions around the focus of your image.

So with digital cameras you can buy 24 mpix digital cameras in both full frame and cropped frame versions. If you put the same lens on both cameras the image from the cropped sensor will look like you are closer since there is less clutter around the subject. To get that same view from the full frame camera you will have to move closer. So the cropped sensor is a lot like making your 200mm lens into a 300mm lens and it does not cost you a penny.

You are correct, the focal length of the lens does not change. The depth of field remains the same as does the perspective you get looking through the lens. So the depth of field of the 200mm glass on a crop sensor body is greater than the DOF of a 300mm on a full frame body. Just another added bonus, eh? For a lot of Tele work it is probably true unless you want to isolate a small subject against an out of focus back ground. Commonly an 85mm lens on a 35mm body is the traditional lens for portraits. This has to do with the distance from the subject to fill the frame and the depth of field of the lens. If the eyes are sharp the ears go a little soft as does the nose. This keeps the viewer's attention to the eyes. With a cropped sensor a 55mm lens gives the same composition but the depth of field at the same aperture gives sharper ears and nose taking interest from the eyes.

Bird photographers are known to use crop sensor cameras as part of their kit since longer lenses above 200mm get really expensive in a hurry so there is lots of cropping involved. If you needed a 300mm lens for the bird but only have a 200mm you go for the crop sensor body. That way your final image has a 24mpix resolution. If you use the full frame body you end up cropping the image and your 24mpix image becomes an 18mpix image. This is noticeable if you are looking for feather details.

So there it all is. There are other details between the formats like pixel size but that is an entirely different class.

Posted from Windows Phone OS 7

The problem with the term "reach" is that it perpetuates the myth that there is a longer focal length from a crop sensor. People and the media repeat this and before you know it, it becomes "fact". It's one of the most widely misunderstood aspects of digital imaging, right next to resolution.

I wish everyone would call it what it is, "crop" or "crop factor", because that is all it is.

trainjunkie Wrote:
-------------------------------------------------------
> The problem with the term "reach" is that it
> perpetuates the myth that there is a longer focal
> length from a crop sensor. People and the media
> repeat this and before you know it, it becomes
> "fact". It's one of the most widely misunderstood
> aspects of digital imaging, right next to
> resolution.
>
> I wish everyone would call it what it is, "crop"
> or "crop factor", because that is all it is.


https://mail.google.com/mail/?pli=1#inbox/14ac2bf3244db1af

And here is a "reasonable" 300mm, but of course his samples are on a high end camera.

I didn't mean to imply there was not good use of the crop sensor for wildlife only what is said above.

Bob



Edited 1 time(s). Last edit at 01/08/15 11:23 by robj.

robj Wrote:
-------------------------------------------------------
> https://mail.google.com/mail/?pli=1#inbox/14ac2bf3
> 244db1af

No workie.

Same here - demands a log in and password.

I hate "crop factor."

This endless calculation determining what a lens looks like in a format you are not using makes no sense to me.

Never in the history of photography was it needed. It only came about because old duffers like me needed help transitioning from 35mm film to APS-C digital.

As far as I am concerned, the need for it has passed and it should now be called "crap factor" for all the obfuscation it causes.

Just learn what focal length looks like with the camera you are using and be done with it.

In a related discussion, yes, a tele lens has more "reach" in APS-C. I hear that all the time. Great for sports, wildlife, trains on the plains.

On the other hand, a wide angle lens has more "width" in full frame. I never hear that mentioned. Great when in close, or on the plains as well.

Dennis Livesey
New York, NY

https://photographylife.com/


Here is a direct link to their site, the article should show up first, think the passwd was because it was linked to my mail.

Sorry about that.

Bob Jordan