Practical Limits of Enlargeability

I have been asked numerous times about how big a print can be made from a digital image. Up until recently, the answer was quite easy: one would need a 200 PPI or higher resolution image for matte papers and 210 PPI or higher for semigloss surfaces. Canvas is a much more forgiving medium, one could go much lower with careful processing. My biggest enlargement, from a 4.5 megapixel original, was printed on Hahnemühle FineArt Canvas in 36 x 100 cm size. This was shot with an 1D Mark II, so this is a 35x enlargement. The print was made at 90 PPI. Yes, this was a result of several hours of careful editing and a matching media choice.

This is a crop from a 8MP image. The biggest print that still looks great is 38×100 cm. But this is an exception in enlargeability, not the norm. Subject matter really helps here.

Of course high resolution is a must for hyper-realistic prints. Posters can be made at much lower resolutions. But I’m not interested in making posters at all. I even wrote an app (PrintCalc), that can calculate all this resolution requirement stuff for you.

To put it another way, digital prints were limited by the sensor’s resolution.

In these days, however, we face another limits. Diffraction, depth of field and lens quality. Let’s take a Canon 5D Mark III for example. The full frame sensor at 22MP starts to get diffraction limited below f/10. The 7D at 18MP is visibly diffraction limited at f/8. The problem is worsened if you want big prints. One often overlooked attribute of depth of field is that it gets shallower as you make bigger enlargements. But you can’t stop down to increase depth of field at your will, because diffraction kicks in. This might, or might not be a problem depending on subject matter.

For landscapes, diffraction puts an upper limit to practical enlargement ratio. You can only go larger if you use a bigger sensor. For other subjects, where you can shoot at wide apertures, this isn’t that big of a problem, so you are limited by the number of pixels. Speaking of the number of pixels: DxO’s new “perceptual megapixels” ranking is a good indicator what kind of resolution a lens can give you. You can increase sensor resolution, but the lens will still be a limiting factor. Think about this perceptual megapixel number as the one you can use as the basis of maximum print size calculations. Look at the best lest they tested to date: Canon’s EF 300mm f/2.8L IS II USM. It can fully utilize a 21MP sensor, but you’ll end up around 14MP on a 18MP APS-C sensor (the 7D).

So it’s easy to see that blindly increasing sensor resolution in any given format above lens capabilities and so much that is severely affects usable apertures is not the smartest thing.

What is that practical limit? I found that about 20 times enlargements (in linear dimensions) make great hyper-realistic prints, keeping ill-effects at a minimum. This translates to about 50 x 75 cm (20 x 30″) for full frame and 30 x 45 cm (12 x 18″) for APS-C. Regardless of megapixels. Of course you’ll need to hit the 200-210 PPI minimum, which is about 11-12 MP for APS-C and 23-24 MP for full frame. But increasing the sensor’s resolution beyond these points will only allow to reap the benefits of oversampling, and not really allow bigger prints at the same quality (not to mention increased storage requirements).

Want bigger? There’s only one way with today’s technology: increasing sensor surface. Basically we have to paths in pursuing bigger recording area:

  • Go medium format. Digital 645 will give you images that can be printed at 80 x 110 cm (30 x 40″) – from an 50 MP or larger file. This costs a lot.
  • Stitch several images together. I routinely use my TS-E 24mm lens to get images equivalent in size to a medium format sensor (36 x 48 mm). This is more work, but at the fraction of the cost of medium format.

20x enlargements are far better than you could achieve (in high quality) from film. This is actually at least one format size better (full frame 35mm beating 645). But remember that every technology has practical usage limits, and make them work for you – don’t blindly believe manufacturers’ marketing stuff.

Canon EOS-1D X and 6D Impressions

Many thanks to Canon Hungary for kindly supplying test cameras for our project!

From time to time a bunch of cameras arrive at my desk for measurements and software compatibility testing. This is a double-fun exercise: besides learning a lot about cameras I have the opportunity to try out and photograph with almost all of them. Among the recent group borrowed from Canon Hungary, there was two cameras I was eager to try out: the EOS-1D X and the EOS 6D. Fortunately the testing period included a weekend, so I had a little more time to go out and play with both, and to compare them with my 5D Mark III and 1D Mark II (which I still have because it can’t be sold at any sensible price).

First and foremost: I would be hard pressed if I had to choose between the 1DX, 5D3 and 6D based solely on image quality. All three are capable of producing great images. You can’t go wrong with any of these. You can also find several reviews on the web doing all the pixel-peeping. So I will concentrate on handling and usability – both playing an important role in my camera selection.

In General

I have been an EOS-1 user for almost a decade, and I immediately felt home with the 1D X. Sure, it is bigger and bulkier than recent models, but at 1550g it’s still 20g lighter than the 1D Mark II. For me this weight dictates the use of the E1 hand strap.

It seems that only the 1-series Canons are designed for people having a nose. Having anything than a small and flat nose is a recipe for discomfort and greased LCD on all non-1 Canons. The 1D X being thicker reduces the distance the viewfinder protrudes from the body, so it’s slightly less convenient than previous models. In comparison: the 5D Mark III is bearable, but the 6D is awful: I can’t see the entire image in the finder without risking to break my nose…

Switching between the 1DX and the 5D3 is effortless: I was able to instinctively find all the controls as they were where they should be. Not so with the 6D. I found the omission of the joystick, the inconvenient selection dial and mixing picture taking controls with playback controls so much frustrating to use that I put down the camera just after half an hour and decided against buying one, despite holding it still feels good. I understand that it’s a sacrifice one has to make for reduced size/weight/price, but I’m rather carrying/paying more for something that’s a joy to use. If I desperately need a cheap/light backup camera then I might buy one, but at the moment I don’t feel that need.

The CF compartment door on the 1D X I tested was loose and emitted a squeaking noise every time I squeezed the body – and you have to squeeze it to be able to pick it up. I don’t know if it’s a problem with this given demo unit, but it’s not something that I experienced with previous 1s and definitely not something I would accept on a $6800 camera. Even the 5D3’s CF door was better.

Features I Miss

Although the 5D3 and the 1DX are from the same mold, there are a couple of pretty useful 1-series features I miss on the 5D3: eyepiece shutter (the 5D3’s plastic thing is a joke), the ability to save the whole camera configuration to a card and load it later, and the ability to lock up the mirror for several shots (which is pretty useful if you do brackets).

On the other hand, the RATE button introduced on the 5D3 and the truly silent shutter of both the 5D3 and the 6D (the silent shutter on the 1DX is pretty useless) are features that could find a home the 1DX.

Things That Need to be Done Fast

All four cameras were pretty responsive, but I was especially interested in a few things. The first was buffer clear time. Lots of people talk about the buffer capacity, but I found the time needed to write all images to disk more important. Even a smaller buffer with faster clearing could be useful. In this comparison the 1D2 lost by huge margin: using a 16GB SanDisk Extreme Pro card it was capable of taking 19 shots (on average) in a burst and it took 15 seconds to clear the buffer. During the last decade it proved to be inadequate more than a couple of times. The 5D3, with a 32G Lexar Pro 1000x card was able to capture 37 images before starting to slow down and the buffer cleared in mere 2.5 seconds! The 1DX was able to capture 58 shots in a 12 fps burst, and wrote them to the same 32GB Lexar Pro 1000x card in 7 seconds. Even the 6D was better than the 1D2: it took 21 frames and wrote them in 8 seconds to a 32GB SanDisk Extreme Pro SD card. In terms of fast capture and fast card writing both the 1DX and the 5D3 are wonderful.

I was interested in how fast these cameras drive a long telephoto (without and with teleconverters). I made no numerical comparisons, just how fast they felt. Surprisingly the 1D2 was the candidate for the fastest lens drive medal, but it has to correct what it did in a second round several times. Maybe its NiMH batteries could provide more power to the lens? The 1DX drove the 500mm f/4L IS quickly and precisely, even with teleconverters attached, so the aforementioned medal went to the 1DX. Lens drive is not where the 5D3 AF system shines. However, my experience shows that its AF system is far better than the 1D2 for tracking birds – even if it drives lenses noticeably slower than its big brother. Here the 6D pleasantly surprised me: lens drive was faster than the 5D3’s! So I sincerely hope that Canon would be able to squeeze out a 6D-equivalent lens drive from the 5D3 with its upcoming firmware update.

The last thing I tried was low light focusing – with the center point only. The 6D is the clear winner here – it was able to focus on features I was barely seeing! The 5D3 took second place, with a bit of hesitation (read: several seconds) before grabbing focus at the same spot where the 6D focused instantly. The 1DX hesitated even more, but was able to grab focus, but the 1D2 was unable to achieve focus in any of my tests.


Let’s start with the easiest one: the 6D impressed me with its low light focusing ability and speedy focus drive, but it was not enough to outweigh its shortcomings in the handling department. So as I mentioned I decided to skip this body for now.

The old 1D Mark II held against the competition pretty well, despite its 9 years in service. I changed my mind about selling it: I would get less for it than a medium level Montblanc pen costs, but its still a pretty usable and capable camera – up to ISO 800. It stays until it dies.

And now the big question: 1DX or 5D3? I bought the 5D3 at the time when the 1DX had no f/8 focusing ability. Would Canon introduce the 1DX with this feature I would end up with that camera, no question about it. But the 5D3 will get that feature in April, so again a tie. Now I see four decision factors:

  • Action-stopping ability (high fps, focus tracking and focus drive). It you need this go with the 1D X.
  • Size/weight. I would take my 5D3 to a vacation paired with my beloved light primes without any hesitation. Would not even think about that with the 1D X (been there, done that with the 1D2 – not again).
  • You get 22% more pixels with the 5D3, which is important for landscapes/architecture. I will do some print comparison between the 1DX/5D3 files in the coming weeks to see how much they differ at 40×60 cm print size.
  • And, of course, price. At $6800 I feel the 1DX a bit overpriced. At the vicinity of $5000 it would be an instant get for many people I believe.

Nowadays I do more landscape and architecture photography than birding, so the 5D Mark III serves me well. Metering and the quality of its files are well above previous generations. The only advantage of the 1DX from my point of view is its action-stopping ability. In all other aspects the 5D3 is a better choice. Should I feel the need for more than 6 fps and slightly faster focus I will grab one.

Oh yes, one way to avoid the above decision is to own them both 🙂