I hear it all the time: I’m thinking about moving to a full-frame camera. It’s getting more common as the price gap between full and crop frame cameras is shrinking, at least to some degree. But often it said as if moving to full-frame is, by itself, an upgrade. As someone who moves back and forth between full frame and crop frame cameras all the time, I see it more as different, not always better. Horses for courses, and all that. Anyway, I thought I’d put some comments down for those who are thinking about the move.
What’s better with full frame?
If we consider the move to be from the top of the line crop-frame to the intro level full frame (A Nikon D300 to D700, or Canon 7D to 5DMkII, for example) there’s often not a huge difference. The full frame will offer either higher megapixels or better high ISO performance, or sometimes a bit of both. The full frame sensor is about twice the area of a crop frame, so if it has the same number of pixels then those pixels will be larger and larger pixels generally mean less noise at high ISO. If the pixels are the same size then the full frame camera will have more of them and offer higher resolution. In practical terms, though, with today’s cameras unless you print very large (more than 11×16 inches), the resolution may not be apparent. Crop-sensor cameras have plenty of resolution for at least an 11×16 print.
The full frame camera also has a shallower apparent depth of field. By this I mean if we change focal length or distance of subject so that the image from a crop frame and the image from a full frame appear to be the same size, the full frame image will appear to have a shallower depth of field. Considering it mathematically, the same lens on either camera would have the same depth of field, but we don’t take pictures mathematically. If I shoot the same outdoor portrait with both a crop and a full frame, the subject taking up the same portion of the image, the background will be more blurred on the full frame.
What’s better with a crop frame.
The biggest advantage is the so called magnification factor, that a lens appears to be 50% longer on a crop sensor than full sensor camera. The reality is that if the cameras have the same pixel density, you could just crop the full-frame image to be exactly the same as the crop-frame image. But if you compare a 12 megapixel crop sensor to a 12 megapixel full-frame, the image of the crop sensor will have more detail than the full frame image taken at the same focal length. This is particularly important for sports shooters, since f/2.8 zooms generally only go up to 200mm and a 300 f/2.8 is much easier to handle (and costs a lot less) than a 400mm f/2.8.
Crop sensor cameras also allow you to use lenses specifically designed for their format. These are almost always less expensive, smaller, and often have similar image quality to their full-frame counterparts. Some crop-sensor lenses just have no full-frame equivalent. There are no 18-270mm or even 18-200mm full frame lenses, so the “one lens solution” is basically a crop-sensor only club. Also, when you do use a full-frame lens on a crop sensor, the camera is shooting through the “sweet spot” of the lens: the weakest part of most lenses are the edges and corners. The crop sensor image circle doesn’t use them.
What’s just different?
Wide angle lens choice
This is good or bad, depending on what you want to accomplish. A 24mm zoom on a full frame body is fairly wide, with an angle of view that’s about what a 16mm would look like shooting a crop sensor. That great 35mm prime is now somewhat wide. This can be a good thing. But at the same time the large selection of ultra-wide crop sensor lenses is no longer available: the 10-22, 10-20, 10-24, 11-16, whatever zoom won’t work. For Canon shooters the 17-40mm f/4 lens is better and not too much more expensive, but for Nikon and Sony shooters the high quality wide zoom for full frame is going to be a lot more expensive. My summary would probably be the wide angle change is a good thing, but the ultra-wide angle lens is going to cost you more.
Prime lens choice
One of the big motivators for many of us changing to full frame is to be able to use the great, top end, wide angle prime lenses that are superb on those cameras. (Yes, you can use them on crop-sensors, too, at least for standard range shooting). But price, again, may result in sticker shock. Those primes are expensive. And particularly for Nikon shooters you leave some very nice DX only crops behind, the 35mm f/1.8 and 85mm f/3.5 Macro, both of which are dirt cheap (well, compared to their FX equivalents) and very sharp. Canon shooters may miss the 60mm f/2.8 Macro for the same reason, and the Sigma 30mm f/1.4 is missing for everyone. But once the sticker shock is overcome, there’s nothing that looks better than a Canon 85 f/1.2 or a Zeiss ZF 85 f/1.4 shot on a full-frame body.
So who should make the move?
Those who need a pro body
I haven’t really mentioned it, because I’ve been concentrating on the not-sure-if-the-benefits-are-worth-it kind of move, but obviously some people have to have the sturdy, large battery, weather resistant body, and on the Canon side more robust autofocus (Canon 1D series, Nikon D series). That move is just a given.
Those who need every megapixel they can get
This isn’t as big a difference as it once was, but for people who shoot for billboards, make large prints, or shoot for glossy print ads need to move to full frame to get every megapixel they can. In most brands that means a move to a full frame camera.
Those who need the highest ISO performance
Not every crop to full frame move improves ISO—if you get 50% more megapixels, with otherwise identical cameras, high ISO performance may not improve. For example, moving from a Canon 50D (15 Mpix) to a 5DMkII (21 Mpix) gives a bit better high ISO performance. Moving from a Nikon D300 (12 Mpix) to a D3 gives dramatically better high ISO performance. Notice I say performance not ISO it will shoot at. Just because they put the ISO number on the menu doesn’t make it usable.
Those who want to use certain lenses
The best example I can think of is why I did it. I loved (back in the day) doing portraits with the Canon 85 f/1.2 and 135 f/2. They are a marvelous portrait lens, but too long for my liking on the 40D I was shooting. They were exactly what I wanted on a 5D. It may sound superficial to some people, but among more experienced photographers it’s one of the most common reasons to change that I know of. But it also works the other way. If I was spending most of my time behind a 500mm lens, I’d rather have a 7D for the increased pixel density to get every bit of telephoto imaging I could get.
Those who want the shallowest depth-of-field
And to repeat, before I get corrected 13 times, the actual depth of field for a given lens at a given distance to the camera doesn’t change. But if you frame the shot to look the same, the perceived depth of field will be narrower with a full frame camera. Videographers, in particular, really want this effect.
Those with years of 35mm film shooting who are just more comfortable with focal lengths acting like they expect them to act.
No, not me. My first SLR was digital. But there are definitely still some ex film shooters wandering around.
Those who just like the look
It’s totally, completely subjective, but some people just like the contrasty look of a Zeiss lens, or the warmer look of a Sigma, some people like the look of a certain full-frame cameras compared to their crop-frame brethren. The difference between a full-frame and a crop frame camera of the same brand is not nearly as pronounced as the difference in look between Canon and Nikon colors, but it is noticeable.
So what’s the summary?
For many people shooting crop or full frame is an easy call. One person wants the high pixel density and crop factor for telephoto work and will never go full frame. Another has to have full-frame for the high-ISO look he wants. For most of us, though, it’s a trade off and one that needs to be thought about carefully. It’s not clearly better to shoot full frame, but it certainly may be better for some people and in some situations. But moving from crop frame to full frame may have drawbacks, too, and these should be considered carefully before making the move.