Using a full frame lens on a crop sensor camera—or the other way around—has its quirks, especially when it comes to field of view, resolution, and camera settings. Understanding these factors can help you make better lens choices for your camera setup, giving you more control over your shots.
Coming to you from David Bergman with Adorama, this straightforward video clarifies the differences between full frame and crop sensor cameras, especially the effects on your field of view and image resolution. Bergman first explains that full frame sensors match the size of a 35mm film frame, a standard in high-end cameras today, while crop sensor cameras use smaller sensors, typically APS-C or micro four-thirds. A smaller sensor means a narrower field of view when using the same lens, essentially cropping the image. Canon crop sensor cameras, for instance, have a 1.6x crop factor, so a 50mm lens effectively gives you the field of view of an 80mm lens on a full-frame camera, which can be useful for adding reach when shooting distant subjects like wildlife.
Bergman goes on to explain that while you can use full frame lenses on crop sensor bodies, doing the reverse requires some adjustments. Full frame lenses project a larger image circle to cover a bigger sensor. A crop sensor body only captures a portion of this circle, which creates the “zoomed-in” effect on the image. However, using a crop sensor lens on a full frame camera is trickier, as the lens doesn’t cover the whole sensor, leaving dark edges around the frame. Some cameras, like Nikon’s DSLR and mirrorless lines, address this with an automatic crop mode, switching to a smaller image area when you mount a crop sensor lens on a full frame body. Bergman mentions that this is convenient because it eliminates the need to crop in post-processing.
An interesting part of this video covers in-camera crop settings, which let you crop into the image directly in the camera. Bergman notes that Nikon cameras, for instance, allow users to choose from multiple crop settings, including a 1.2x or 1.5x crop, or even a square format. These options can help if you need a specific aspect ratio or a tighter crop without doing it in post. However, Bergman prefers to avoid these modes, explaining that it’s often better to capture the full image and decide on cropping later, preserving as much resolution as possible. You also need to be careful with full frame DSLRs, as the mirror can sometimes strike an APS-C lens.
Bergman also touches on practical uses for these crop modes. Using a crop setting can improve burst shooting speed and save storage by recording a smaller area, which could help when shooting action. However, for general use, it’s often best to avoid in-camera crops in some models, as they lock you into a specific crop that you might want to adjust in editing. Check out the video above for the full rundown from Bergman.
In the days of the FD lenses at Canon I always shied away from the 7.5 mm because it would just fill a circular area on the film.
When I heard this story about crop lenses on full frame bodies I was just wondering what that would be good for ...
Okay, so if there is no problem getting in the way of a mirror, then why not. But using a crop function built into a full frame body and thus artificially reducing the sensor resolution by ignoring a good number of pixels I effectively turn my expensive full frame camera into a crop model, without getting any money back.
It is one thing to use existing full frame lenses on a crop body rather than spending more money by buying specific crop lenses, but the other way around doesn't make a lot of sense to me.
Also, I find the crop factor somewhat irritating at times. Back in the days when I was still angry at Canon for making the EF mount incompatible with my collection of FD lenses (some of them superb) I went ahead and bought a M43 body and an adapter. That all worked pretty well, except that my FD 85 f1.2 portrait lens turned into an effective 170 mm lens with great light power, which is nice, but not as useful as my 85 mm lens would be (I could of course make Canon rich by buying that lens all over again in the EF version - and now again as an RF lens ...)
But the 35 mm and the 55 mm lens make decent portrait lenses, and some of the telephoto lenses give good results in the game parks of Africa.
I am totally disappointed, though, when I think of what became of my 15 mm and 20 mm lenses ...