Petteri's Pontifications
My musings about photography, mostly.
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To Full-Frame or Not To Full Frame?

To Full-Frame or Not To Full Frame?

The release of Canon's newest digital SLR, the EOS-5D, has brought full-frame digital capture within reach of a new group of photographers. It costs just about the same as the ground-breaking EOS-D30 did when it was announced. Three grand is still a lot of money, but it's not in the sell-your-car territory where full-frame has hitherto resided (not counting Kodak's efforts, which are in skilled hands capable of incredible quality, but have some serious limitations compared to more mainstream cameras). With used but eminently serviceable EOS-1Ds's on the market too, going full-frame is now a realistic option not only for full-time pros but also well-heeled amateurs and semi-professionals. However, full-frame high-resolution digital capture is something of a mixed blessing. Nikon isn't blowing smoke about the issues with it. It's much more challenging to shoot than APS-C in more ways than one -- but also immensely rewarding. Is it worth the expense and effort? Read on...

In film-based photography, the number three factor limiting image quality is and has been film. For this reason, when discussing capture size and image quality, bigger is better. So, while 35 mm film has hit a very sweet spot of quality, cost, and convenience, larger formats have thrived alongside it, both among professionals and amateurs. While the digital revolution has stirred the pot somewhat (most digital cameras by far have tiny capture formats, as small as or even smaller than 1970's toy cameras using formats like 110, or those funky ViewMaster-style disks), the principle remains the same. That's why there's a clear and pretty much undisputed difference in image quality between even the best small-sensor compacts and even the cheapest digital SLR's.

Limiting factors one and two are, of course, skill and circumstances -- you really have to make a serious effort to max out the quality of a decent bit of 35 mm film.
landscape

No need to turn up your nose at the small-sensor compacts either. This is from one, and it prints plenty fine up to 20 x 30 cm. Beyond that the going does get a bit mushy.

It is pretty obvious just from looking at the kinds of cameras people are buying and shooting that digital capture produces a good deal better image quality per square millimeter of capture than film does. Film cameras with formats the size of digital compacts have been tried, and their limitations are woefully obvious even at 10 x 15 cm and even at slow film speeds. Good digital compacts can turn out a splendid-looking 20 x 30 cm without breaking a sweat, and for the right subject shot and post-processed the right way, there's virtually no upper limit to the print size you can get. Digital SLR's clearly exceed the quality of 35 mm film for most practical purposes and most print sizes. APS-C has hit the same sweet spot as 35 mm film did back in the day -- reasonably inexpensive to produce, possible of quality that's easily up to most applications.

So, given that a full-frame chip will cost approximately 12-16 times more to produce than an APS-C chip, and given that sensor evolution isn't over by a long shot, is there any point in going after bigger formats?

There Ain't No Such Thing As A Free Lunch

The "format war" in digital photography pits two groups of designers against each other. The bigger you make the sensor, the greater a burden you lay on the optics designers. The smaller you make it, the greater the burden on the sensor designers. The cost and difficulty of producing optics is something like a function of the cube of the capture size, at least for wide and normal focal lengths and at least above a certain minimum size. That's because a lens is a three-dimensional object. Double the radius of the image circle while keeping the optical formula identical, and your lens will have to weigh eight times as much. Keep the pixel pitch on the sensor the same, and your larger lens will have to be twice as sharp (because the aberrations get enlarged right with the picture, when you scale up the design) -- which means a different and more expensive optical formula and/or tighter manufacturing tolerances. In other words, when making the sensor bigger, there will be a law of diminishing returns, since the weight of the limiting factor shifts from the sensor to the glass.

Different manufacturers have taken different guesses about where the happy middle lies. Olympus has gone with a sensor about a quarter the size of a 36 x 24 mm film frame, 4/3. Canon has indicated that it sees 36 x 24 as the future for professional and high-end amateur digital imaging. Nikon (and most of the others) have put their money on the APS-C format, about half the area of a 36 x 24 frame. And beyond full-frame lie the Olympian peaks of digital medium-format and scanning backs.

ground zero

If this were shot on film, it would inevitably have been shot on 35 mm. Actually I shot it on APS-C, as indeed are most digitally-originated photos of this type.

My gut feeling when looking at what's available now and what it needs to do is that the successor to 35 mm film is, indeed, digital APS-C. Full-frame is a little too hot (most lenses at most apertures and most focal lengths can't quite keep up with the demands of the format, and the chips are difficult and expensive to produce, at least at the current state of the art), while 4/3 is a little too cold (Olympus has been forced to come out with monster f/2.0 zooms to provide even rudimentary available-light capacity, given the comparatively poor high-ISO performance of at least the current 4/3 sensors), while APS-C is just right -- the sensors sharp enough and fast enough for almost any purpose, without putting too burdensome demands on the lenses.

Technological advances can and very likely will change this equation. Chip prices will continue to come down, which decreases the price handicap of full-frame. On the other hand, chip quality will continue to improve, which decreases the capture quality handicap of 4/3. I find it unlikely that the constraints of glass design will change much, which means that the optics advantage of 4/3 and APS-C will become relatively more important over time as the sensor advantage of the larger format becomes less important. Four-thirds could still have a shining future.

Yet I don't regret blowing a bigger sum of money than I have ever spent on a consumer durable on the EOS-5D. Not one bit. Am I nuts? My wife thinks I am. On the other hand, my dad's reaction to the 5D was "I've gotta go and get me one of those!" By going full-frame, you lose a big wad of money and some other things as well, but you do win something too.

What You Lose

Corners on wide-angle and open apertures. When examining a wide-angle picture shot with a Canon full-frame dSLR, Nikonians like to giggle and point at the corners.Indeed, often, there is something to giggle at. I do not know of any ultrawide (say, 20 mm and below) that will produce impeccable corners on full-frame digital at all or even most apertures. On the other hand, the reduced-circle ultrawide zooms from Canon, Tokina, Sigma, and Nikon (that 12-24 DX is absolutely gorgeous!) are more consistent than anything comparable for full-frame, even near-legendary glass like the Zeiss Distagon 21/2.8. You can get sharp corners on them if not wide-open, at most a stop or two down.

worst case

The worst case scenario: the 20/1.8 wide-open, top left corner. Nice, if you like blur -- seriously this effect does have legitimate creative uses -- but probably not what you shelled out your hard-earned for. And, believe it or not, even this amount of blur isn't as noticeable in print as you might think -- so don't write off those open apertures.

However, this doesn't mean that you can't get sharp corners on full-frame at all. You most definitely can. My Sigma 20/1.8 is a solid lens, but by no means royalty, and it will produce an impeccable frame corner to corner when focused on infinity and stopped down to somewhere between f/11 and f/16. (With the pixel pitch on the 5D, diffraction isn't yet noticeable, if indeed it's detectable at all at that aperture, although on the higher pixel pitch of the 20D it was visible if you looked for it.) Even my pretty extreme 14/2.8 doesn't look too shabby in the corners at small apertures. I'm sure there are other lenses out there that can do even better; from what I've seen on the Net, the Distagon 21/2.8 produces sharp corners by f/8 or so, for example. However, I have a feeling that most lenses that did splendidly on APS-C, especially most consumer wide zooms, will look pretty dismal on full-frame, even at the smaller apertures.

best case

Same lens, stopped-down, bottom right corner. Not too shabby in my book.

So, the first and most obvious thing you lose is sharp corners on wide-angle lenses at open apertures. In practice, this means that if you're shooting a landscape for a big print, you need to stop down and do it off a tripod, unless you're shooting it in bright sunshine. And if you're relying on a consumer-grade 24 or 28-something for your wide-angle, you'll probably be wanting to buy a better lens pretty soon.

Someone would probably add, "Well, duh!"

So, the "soft corners at wide-angles" issue is certainly not imaginary. However, it's also important not to overstate it. For available-light hand-held situational shooting it doesn't really matter, since the corners will hardly ever be in focus anyway. For prints around 20 x 30 cm and below, it doesn't matter much either, since the softness won't be immediately noticeable at that size. It only matters for a specific kind of picture, and for that kind of picture, it means that the photographer needs to take more care when shooting it. And it means that consumer-grade wide-angle glass will fall short, which means more expensive or otherwise more limited lenses. It's a good deal easier to get good sharpness across the frame with wides on APS-C than it is on full-frame, and depending on the circumstances, it may make the difference between getting a shot and missing it.

The vignetting thing. Another thing that APS-C proponents like to point at is vignetting. Shoot a frame of the sky, a white wall, or any uniform-colored subject with your lens wide-open on full-frame, and the same frame on APS-C. Chances are, the full-frame picture will show pretty obvious vignetting -- the corners will fade into darkness, a stop or more. This can be a bit of a shocker especially if you've just dropped several grand on a full-frame camera and top-drawer "L" lens -- and easy to seize on if you're looking for sour grapes material.

vignetting

Vignetting: the worst-case scenario. Four of my lenses wide-open on a flat, monotone subject. Clockwise from top left, the Sigma EX 14/2.8, Canon EF 50/1.4 USM, Sigma EX 20/1.8, and Canon EF 35/2.0. Of these, I'd qualify only the 14/2.8 as "severe" -- but wide-open, vignetting is the least of its edge problems anyway.

But in practice, it really doesn't matter. First off, it goes away simply by stopping down. Second, what's left of it is easy to fix as good as undetectably in post-processing. Third, on most real-world subjects, you won't even see it. It simply gets lost in the chaos of a real-world subject, with blurry background or foreground objects of different colors mostly filling the frame. And finally, on the rare occasions when you do see it, don't have the option of stopping down, and can't or don't want to post-process it away, it can actually look pretty damn cool -- it is, after all, a characteristic of capturing an image just like limited depth of field. So if you're looking for arguments not to go with full-frame, vignetting (while certainly a real phenomenon) is a pretty weak one.

On the other hand, you can always fake it in afterwards if it isn't there. In fact, I occasionally do.
vignetting?

Now you see it, now you don't. This is the same 20/1.8 at an open aperture (f/2.8), on a real-life subject. Where did it go?

Depth of field. APS-C has at least one and a half times the depth of field of full-frame, at any given field of view and aperture. Sometimes this is a good thing. Sometimes it's not. It also means you have to be more careful when focusing, and any miscalibration in your equipment will be more obvious.

dof

Reach. Well, kinda. With telephoto, you'll want to put as many pixels as possible on your subject. Currently in the Canon line-up, this would mean the 20D or 350D... or the stratospherically-priced 1Ds Mark II. The Nikon D2X beats all of the Canons in this respect. However, in my opinion there are precious few telephoto shots where the difference between, say, 6 and 12 MP really means much -- that's enough to resolve all the fine detail of a bird, beast, or football player. The experience of shooting with a telephoto on APS-C is certainly different, but if considering purely the end result, you'll get more or less the same by cropping the full frame. Still, if telephoto is your main concern, it'd be a bit pointless to shell out all that money for a full-frame sensor and then only end up using the center, no?

Dust bunnies. Or, rather, you win dust bunnies. Double the sensor area, double the amount of dust. Plus, you'll be shooting your lenses stopped-down a lot more, which means it'll show up, too. So, despite what Canon says, brush up on your m4d sensor-cleaning sk1llz, because you'll be using them. Again, hardly a showstopper but definitely an added chore.

What This Means

All this adds up to the same thing: to make the most of the camera, you need to work harder. In situational stuff, you need to be more careful with your focusing technique. In deep field of focus static stuff, you need to stop down more and use a tripod. So, if you're expecting that your three grand will magically improve your photography, you're in for a rude awakening -- until you figure out what you need to do, your pictures will, in fact, look worse. Mine certainly did. But this isn't rocket science either -- all it took to correct the problems was one practice session with shots with various lenses and various apertures, and an adjustment in technique to compensate for the tighter constraints that emerged. By Day Three of my experience with the 5D, I knew what I had to do to max out the sensor, or close anyway. It shouldn't take longer than that, if you have a basic understanding of photographic technique and are willing to do the work.

There's another option: shoot at any aperture you like and crop. A full-frame camera is also an APS-C camera. All you need to do is crop out the edges. On the 5D or 1Ds Mark I this will end up as an approximately 6 MP APS-C capture, depth of field, edges, vignetting and all. In fact, at least on my wides the edges at open apertures really start to deteriorate somewhere between the APS-C line and full-frame, which would leave you with perhaps 8-10 sharp MP, so cropping them out is certainly a viable option, and if everything else went right will end up with a picture good enough for even pretty huge print sizes. It would be kind of silly to make this the mainstay of your technique, though, since you might just as well have gotten the smaller-format camera to start with.
outside

What You Win

More pixels, at least if you're a Canonian contemplating an upgrade from a smaller-format dSLR. This doesn't really mean that much per se; if talking about raw pixel count, the difference between 8 and 12 is pretty subtle -- to really see a difference even at print sizes where it matters you would have to double it or more. For most practical purposes, 6, 8, or 12 MP wind up as the same -- "enough."

Better pixel-level quality. I don't know if this is intrinsic to the larger format or just a matter of Canon's implementation, but I am seeing a difference in my 5D captures compared to my 20D and 10D captures as well as some Nikon D2X captures that a number of people were kind enough to let me have. They're somehow more "alive" and "three-dimensional" when viewed at actual pixels or printed out at largish sizes. In particular, fine textures like fabric or rock come alive and "pop" out of the picture in a way that none of the APS-C files I've seen quite manage to pull off... other than files from the Sigma dSLR's, that is.

outside

An actual-pixels crop from the 5D. None of my previous cameras has come close to this "look," whatever it is. Do you see it too?

I suspect this may be due to the less aggressive antialiasing filter in the 5D than the 10D or 20D; after all, the 10D has roughly the same pixel pitch as the 5D, yet the pixel-level quality doesn't quite match even the 20D's. I do see a good deal more moiré in the 5D files than I'm used to seeing on either of my previous cameras. I would rank the Nikon D2X files I've seen as superior than my 20D and 10D files, but not quite as good as the 5D files, although they do come damn close. This is obviously highly subjective, and I'm quite certain that others will prefer one of the other files. However, the Nikon files are so good that I am pretty certain that we won't have to wait long to see as good maximal attainable quality in an APS-C camera as we now find in full-frame ones.

More sensitivity. More pixels and bigger pixels means less noise and a tighter noise pattern. ISO3200 is a cakewalk even in JPEG, and with some RAW diddling, ISO6400 is eminently usable and even ISO12800 isn't science fiction. This is perhaps a stop more usable sensitivity than I got on the 20D. The downside is that because of the advantages of stopping down, you'll be using that extra sensitivity for hand-held shooting more often than you'd think. However, it does give open up more terrain for available-light shooting, no question about it.

high-iso

Shot at f/1.4, ISO3200. No other way to freeze the motion -- no other way to get this exact picture. It's a whole new world of photographic opportunity, that I've only started to explore. No particular noise reduction used at any level.

More dynamic range? Who knows. Perhaps. I never felt this was a major issue with the 20D, and it certainly isn't one on the 5D. This being the case, I can't really say for certain whether the 5D is better and if so, how much better. I'll leave that to others to measure, but Chuck Westfall of Canon says so, and I see no reason to disbelieve him. Make of it what you will.

A bigger viewfinder. Nope, it doesn't really mean much in terms of which pictures you can get and how well you can get them, but boy is it lovely. This is probably the biggest irrational reason to go full-frame, and probably the hardest thing to give up for a film shooter going with APS-C digital. Canon viewfinders are pretty ho-hum as viewfinders go (Minolta, Nikon, and Pentax all do better at almost any price point), but compared to even the best APS-C viewfinders, there's really no comparison.

Lenses behaving like they were meant to. For me, this was the clincher. I'm a prime aficionado, and they don't really design new primes any more, especially for APS-C. Well, OK, there are a couple of macros and the Sigma 30/1.4 which ought to be excellent but I got a poor copy of one. However, the bottom line is that now my lenses behave like they ought to behave: I don't need to settle for average bokeh and only f/2.0 on my normal (yeah, the 35/1.4L would've fixed both of these, but at a major weight and cost penalty), I don't need to carry around a big, mean bucket of glass for my wide-normal, I don't need to put up with an enormous number of flare spots on my ultra-wide, and I'm getting my money's worth of field of view on my hyperwide. And I can eventually add a cheap but lovely portrait lens, like the 135/2.8 SF, for example.

high-iso

"The Wild Bunch," Helsinki, October 2005. I shot this with the 35/2.0, in the way it was intended to be used. It's a great focal length for street shooting, and unlike the 20/1.8 that was doing that job on the 20D, handles extremely well for fast and discreet shooting.

The bottom line

A full-frame camera is more satisfying to shoot and, when handled right, produces even better image quality than an APS-C camera. Whether these advantages outweigh the negatives, especially when considering the much higher cost of both the camera body and the better glass it needs to feed it, is a different question. For some people, the expense and inconvenience of a Hasselblad is worth the improvement in image quality and the satisfaction of using an enormous viewfinder and a camera system engineered to incredible levels of precision. For most, it's not. Unfortunately, a 35 mm based digital SLR isn't a Hasselblad, but in terms of image quality, shooting satisfaction, and to a degree price, it stands in the same relationship to APS-C digital as medium-format stands to 35 mm film. Like 35 mm film, APS-C digital is significantly more convenient, easier to shoot, and less expensive than full-frame digital. So, if you're standing on the fence and wondering what it is you're missing out on, the answer for most people would be "a luxury." Full-frame is in no sense of the word a necessity for the vast majority of purposes and photographers, and the ones who really do require it won't need to read this piece of pontification to know that they do. But if you can afford it and are prepared to go the extra mile when it comes to shooting technique and choice of glass, it is immensely satisfying. It would take a lot to tempt me back to APS-C.

portrait

Joanna, October 2005. Taken with the cheap-o Canon 55-200/4.5-5.6 II -- a lens that has aspirations way above its station.