Some advantages/disadvantages of full frame and APS-C "crop" cameras are:
- Full frame generally offers better low light/high ISO performance. FF image usually show less image noise because the much larger sensor is less crowded, making for less heat and crosstalk, both of which tend to cause noise.
- Less magnification needed for enlargements with FF cameras, as well as larger pixel sites capable of capturing more fine detail will generally make full frame a better choice for really big prints. Up to about 13x19" it will not be very apparent, but any larger than that you'll likel start to see some differences. If you never print large, or if you never print at all, only share images online or as email attachments, the differences won't be apparent. But if you do print big (or heavily crop), it will be more obvious.
- Full frame cameras allow wide angle lenses to be truly wide. But they also demand longer telephotos which will be a lot bigger, heavier and considerably more expensive.
- Full frame offers a bit more control over depth of field. DoF doesn't actually change from one sensor format to the next... However, because when using FF we need to either move closer or use longer focal length lenses (both of which do directly effect depth of field), larger aperturess appear to give stronger blur effects. At the other extreme, because FF are a little less susceptible to diffraction, somewhat smaller apertures are possible too. The difference is about a stop's worth, at each extreme. Also, FF cameras often seem to give smoother gradations (less "banding"), which can make the transitions from sharp to blurred appear "smoother".
- A disadvantage is simply that full frame cameras require full frame lenses. That gives you a little less choice. I'd guesstimate about 1/4 of Canon's lens line-up are "crop only". Also, because they need to produce a larger image circle to fully cover the bigger sensor, full frame capable lenses are necessarily larger, heavier and typically more expensive. Of your current lenses, only one (the 18-55mm) appears to be a "crop only" lens that would definitely need to be replaced, if you choose to go with a full frame camera model. But you probably use the EF 50/1.8 as a short telephoto/portrait lens now, and might need to replace that with an 85/1.8 for similar purpose... Or if you frequently use the 300mm end of your tele-zoom you will need a more powerful telephoto of some sort. I hesitate to make more specific lens recommendations, because we all have our own likes and dislikes. For example, I use a 24-70/2.8 lens that might be similar to your mid-range zoom, but when shooting portraits I like it best on a crop-sensor camera. On FF it just seems a little "short" for portraits (I mostly use 85/1.8 and 135/2... or if I need a zoom a 70-200mm).
- APS-C cameras have a "free 1.6X teleconverter" effect, making any lens behave as if it's 1.6X longer focal length without the light loss "penalty" such as is inherent in an actual teleconverter. This is great for telephoto work... but not so much for wide angle shooting. Many "crop only" lenses offer particularly wide angles of view, for this reason.
For your primary stated purposes, a high quality crop-sensor camera such as the 80D would likely be more than adequate. You would be able to make excellent images to illustrate marketing materials and certainly for online uses. However, for some other things you may prefer full frame... Personally I use both formats: Crop cameras for sports & wildlife... Full frame for portraits, landscapes, architecture. I've used both for macro and close-up work.
Are you also shooting the videos on your school's website? Most Canon DSLRs are capable of video, but there may be some minor differences that you should research and compare. There's more of a difference when it comes to lenses for video work, depending upon the techniques you use. For example, STM lenses are quieter and smoother focusing and preferred for video. However, several recently introduced lenses use a new "Nano USM" form of focus drive that's not only faster than STM (better for any sort of action photography), but also are optimized for video work. One of those is the EF-S 18-135mm IS USM that's often found in kit with the 80D. Also, Canon is offering a PZ-E1 Power Zoom module especially for that "crop only" lens, that videographers might appreciate. (Two other "Nano USM" lenses are full frame capable: EF 24-105mm f4 IS USM "Mark II" and the EF 70-300mm IS USM III... There isn't a power zoom module made for them and Canon doesn't promote these for video in the same way, but I suspec they'd have the same benefits as the new 18-135mm.)
Hope this helps with your decision!
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Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7DII (x2), 7D(x2) some other cameras, various lenses & accessories
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