Comments on: Crop Factor Explained

By: Sarah

Sarah — Fri, 13 Jan 2012 19:55:46 +0000

Why do we even need to know this?! It’s so confusing and does it make me a bad photographer if I really don’t understand it all?!

By: Sully

Sully — Sun, 11 Sep 2011 14:49:18 +0000

I think this article is lacking any information on angle of view. For example, consider a 35mm format (24mm x 36mm) compared with APS-C (14.9mm x 22.3mm). Both sensors have the same aspect ratio, 2:3. Now suppose you have a 50mm lens mounted to these two camera. The optical center of the lens will be 50mm from the sensor. In the long dimension, the 35mm sensor will extend 18mm to each side of the optical axis, but the APS-C sensor will only extend 11.15mm to each side. Talking the arctangent (the angle formed by the opposite and adjacent sides of a right triange) of these ratios 18/55 and 11.15/55 gives 35.7 degrees and 24.0 degrees respectively (for half the field of view), and the whole fields of view are (finally) 71.5 and 48 degrees. The 35mm sensor effectively has better peripheral vision.

For example, if you took a picture of a building from 50 feet away with a 50mm, the 35mm format sensor would see 36 feet of the width of the facade (because the sensor is 36mm wide), while the APS-C would only see 22.3 feet. This appears as if 7 feet of the building on each edge of the image got cropped out. So, if you want to capture more of the building, a larger sensor is better, but if you want to capture a close up of the front doors, for example, the smaller sensor is better (given the same focal length and camera placement). To get the same width of the field of view as the 35mm sensor at 50 feet, the APS-C sensor would need to be 1.6 times the distance from the building, at 80 feet.

Now, when it comes to printing, many of the APS-C and 35mm sensors have the same number of pixels, but each pixel is physically smaller on the APS-C sensor. Sensor size therefore has little effect on the sharpness of large print sizes. This is why the number of megapixels is more prominently advertized than sensor size.

With a SLR camera, the view in the viewfinder is what the sensor will record. Back to the building example, if you take a picture while viewing whole building with either format (or any lens), the whole building will be recorded in the image. Now, many of the top-of-the-line cameras not only have 35mm format sensors, but they also have a 100% view through the viewfinder, while the midrange (for example Canon Rebel T2i) will only have 95% of the sensor image show up in the view finder. An example of this is when I ignore the rule-of-thirds and compose a shot to fill the viewfinder from top to bottom (going back to our building example to have the facade stretch from bottom to top and cutting out all the ground and sky). When I look at the resulting image on the camera’s screen, there shows up extra area that I did not see in the viewfinder (some of the ground and sky). This is not the crop factor. Canon refers to it as “viewfinder coverage”.

By: owner of 600d & d90

owner of 600d & d90 — Wed, 07 Sep 2011 06:00:18 +0000

i have the same question as ridwan above, can anyone provide a better answer?

By: Dave

Dave — Fri, 02 Sep 2011 00:17:46 +0000

I appreciated your post concerning a crop camera body and also the comments that followed.

Information like this leads to better buying choices. When I purchased my first DSLR, no one explained this to me. I think if they did, I would have bought a different camera body.

By: gaspard

gaspard — Sun, 14 Aug 2011 15:40:17 +0000

What I do not understand is that if a picture is cropped, how does that increase the zoom distance? Presumably all that occurs by cropping a picture is a reduction in the size of the rectangle around the picture and the resulting loss of some of the picture outside of that area in comparison to a full frame sensor. How does it bring you closer to the scene i.e zooming in?

By: Dan Johnson

Dan Johnson — Thu, 19 May 2011 21:31:30 +0000

Timen- the only full framed DSLR is canon’s mk1/2/3, and the 5d.

WRONG! Canon, Nikon, and Sony all have full-frame sensor DSLRs at the top of their respective lines.

By: Ridwan

Ridwan — Tue, 19 Apr 2011 09:22:41 +0000

So a small crop factor is not alwys bad, think of it this way, you want telephoto and you have a 2,0x crop factor.
instead of buying an expensive 1200mm lens on a full frame camera (the camera also costs a fortune)
buy a DSLR with a 2,0x crop factor (cheaper) and a 600mm lens and you’ll end up with the same result as the first example, a 1200mm DOF. Can someone confirm me this is true ? if so why would anyone buy a full frame camera unless he is searching for that maximum wide angle (when is such a wide angle used?!)
Thanks for your replies

By: lyne

lyne — Fri, 18 Mar 2011 17:09:11 +0000

I love the landscaped look of a Full Sensor camera. But before I really started getting into my camera and doing more research (after I purchased a crop sensored camera) I realize I want to achieve the same look…How can I use my crop sensored camera to achieve the same look?

Thanks in advance!

By: Chris

Chris — Wed, 17 Nov 2010 16:27:23 +0000

Maybe I am dense, but it doesn’t feel right to state that a 10mm lens is actually a 16mm lens on a camera with a 1.6x crop factor.

Now, correct me if I’m wrong (because I probably am!), but if you took a full frame camera and took a picture at 16mm and compared it to a photo taken with a cropped camera taken at 10mm, the full frame camera should actually be closer. Using the diagram from the original post, it is essentially like a widescreen movie vs fullscreen. You’re just cutting some of the image out, you’re NOT increasing the size of the image, which actually going from 10mm to 16mm is doing, correct?

By: james pickett

james pickett — Thu, 14 Oct 2010 17:01:31 +0000

Mark, you dont always need 300 dpi. I have printed 21mp files from a 1dsmk3 at 31dpi with zero loss. 100 inches high on the short side. I repeat, zero loss or interpolation. The printer Demanded at least 150 dpi, i told them to just print the file and call me back… an hour later “I cant believe there is no loss in this image, How did you know?” was the phone call i got… and these guys have been in the business for over a decade.