When photographers are interested in buying a full frame camera for the first time as an upgrade from their crop frame DSLR, they often have a nagging question. Most photographers have heard there is a difference in the field of view (how much of the scene you can see) when using the same focal length of camera on either a crop frame or full frame camera. So, they want to know how much of a difference it will make.
If you're brand new to this concept, you can check out this article, where I discuss the difference between crop and full frame sensors.
They usually aren't sure how to phrase this question, so they ask something like these questions:
- Do you have any comparison photos of the mm difference between crop frame and full frame cameras?
- I know my crop sensor camera is cutting off some of the picture, but how much?
- What does a picture look like at 18mm on a crop frame camera, compared to 18mm on a full frame camera?
Field of View, and How it is Impacted by the Crop Factor
Field of view simply means the amount of the scene that you can capture in one frame. A full frame sensor is physically larger than a smaller crop frame APS-C sized sensor. This physical difference in the size of the sensor changes the physics of how the lens focuses the image on the sensor. The larger sensor captures more field of view than the crop frame camera if all else is equal.
The sample picture below shows a picture taken at 18mm on a crop sensor camera, and the same picture at 18mm on a full-frame camera. The difference is quite surprising.
Focal Length Equivalents
Please keep in mind that not all crop sensor DSLRs have the same size sensor. The crop factor on APS-C crop sensor DSLRs from Pentax, Olympus, Sony, and Nikon is 1.5. The crop factor for most Canon DSLRs is 1.6x. That means that if you take an 18mm lens and put it on a Canon and Nikon, the Canon picture will be slightly more zoomed in.
On the table below showing the equivalent focal lengths of a full frame and crop sensor camera, I have used the more common 1.5x crop factor. Canon cameras will be ever so slightly more zoomed in than even what the table shows.
According to the table above, for example, you would have to use a 75mm lens on a full frame camera in order to get a photo with the exact same field of view as a photo from a crop sensor camera shooting at 50mm.
WHY Does the Sensor Size Change the Field of View?
Physics, that's why! Remember that the job of the lens is to take a scene and focus it to a small area. The lens creates the reflected scene and puts it on the image sensor, which records the light focused by the lens. Naturally, the larger the sensor is, the more of the focused image it can see. If you're more of a visual learner, check out the picture below that explains the concept.
If you'd like to learn more about how your camera works and the basics of photography, you might consider taking my 30-Day Beginning Online Photography Class.
So is Full Frame Worth the Extra Cost?
It depends on what type of photography you're doing. It's easy to say that full frame is better, but that's not necessarily true. For example, if you don't have the money to plunk down on extremely expensive super telephoto lenses, then you may want the crop factor of a crop sensor camera to help you shoot wildlife or sports. If you're a landscape photographer, then you may want to spend the extra money on a full frame camera to help you go wider.
If you are in the market for a full frame camera, however, you should really take a long hard look at the Canon 6D or the Nikon D600. These cameras are only a few months old and are MUCH less expensive than full frame cameras have traditionally been.