How to Get Sharp Enlargements: Breaking the Megapixel MythPosted by drfl on November 18th, 2009

Myth: More megapixels will always lead to a sharper enlarged image.

This is without a doubt the greatest myth perpetuated by the camera industry today.  Marketing tells us more megapixels=better camera.  Back in the film days there were only a few choices, 35mm, 4×5, 8×10, 110, etc. In those days, (with a few exceptions, of course) the film size DID dictate how far an enlargement could be taken.  I remember years ago taking my 35mm black and white film that I had developed in the dark room and making test strips, then enlarging it to 6×9 and then to 11×14.  The sharpness of the image would begin to break down around that point.  The three main things I had to remember in achieveing the sharpest, largest prints in those days was 1: Shoot big film. 2: Proper focus when taking the photograph and 3: A grain finder.  For those of you who don’t know what a grain finder is, well, let’s just say its the equivalent of 100% zoom in Photoshop.

So, if larger film led to sharper, larger enlargements, shouldn’t more megapixels do the same thing?  I mean after all all those technical sites speak about resolving power and lines per inch and its always better bigger – right?

Well, the answer is somewhat elusive and lies in three basic parts.

1. Film size and megapixel size are not equal comparisons.  More megapixels are being pushed into the same size space.  Most camera sensors today are actually smaller than the 35mm film of yesterday.  That means that the process of enlarging that image is the same, it just means that the details are smaller.  The smaller something is to begin with, the less it can be enlarged without quality degradation at the smallest level. 
2. Logic should dictate that based upon #1, crop sensor cameras may not make very good enlargements. To get to the bottom of this answer, we need to look at how close one looks at a print. Most individuals who look at art for art’s sake will take in the piece as a whole. They may focus on select sections of the image, but overall when someone hangs an image in a room they are not going to put their nose to the glass. Simply put, the only people who care about resolution of print sizes are pixel peepers and they are generally too ingrained in the technical aspects of an image to appreciate the composition for what it is (art!). The larger a print, the further away one normally stands. A billboard, for instance, will normally be viewed from very far away. If you were actually pasting the billboard up there, though, the resolution would look horrible right up close (degradation at the smallest level). A prime example? This image used on a billboard earlier in the year was from a Canon 20d – An 8 megapixel 1.6x crop camera – and of that approximately 60%-70% of the image was actually used (to crop to a billboard format) and it looked great from the road.
3. Based upon the information in #2, we can conclude that most digital cameras produced within the last few years will produce acceptably sharp enlargements. This answer is a resounding “Yes!”. The problems lie not with the cameras, but with the photographers. Now I’m not going to tout the old adage that the camera doesn’t matter, because it does. But there are things that matter more, especially when producing the best possible image for enlargement. Remember, images can always be softened after the fact, but it is very hard and most of the time impossible to add sharpness where sharpness does not exist. Experience has taught me that these are the 4 keys to sharp enlargements:
   1. If you care about gear (and we all should at least a little), make sure that the majority of the money is used on lenses. Cameras make a difference, but a great camera with a soft lens will always take soft photographs. Lenses work on generation after generation of cameras too, so lenses are generally a one-time purchase, if you buy quality to begin with.
   2. Focus, focus, focus. If your subject is not in focus, it will appear fuzzy and that fuzziness will also be enlarged.
   3. Choose the right depth of field. Of course, determining what the right depth of field in your situation takes practice and patience. One hint is that if you want everything in the frame sharp, learn about hyperfocal focusing. The smallest or largest aperture never the sharpest, the sharpest is somewhere in between. Get to know the limitations of your lenses.
   4. Make sure that your shutter speed is fast enough to stop the action, or camera shake. If you shake too much or are using a slow shutter speed, use a tripod. Once again, this is a personal discovery with some guidelines available – namely keep the shutter speed 1 over the focal length. For instance, if you are shooting with a 50mm lens, the shutter speed should be at least 1/50 on a full frame sensor or 1/80 on a 1.6x crop. The longer the lens the faster the necessary shutter speed.

That’s it! If I had two choices, one an image that met those all requirements, but on a 6 megapixel camera or two a 21 megapixel beast with one of those four off, I would choose the former. Simply, sharpness enlarged more will almost always trump fuzziness enlarged less.

Technical Details: Canon 5d, 17-40 f4/l @ 19mm, f/18, 1/10 sec., Tripod
Maligne Lake, Jasper National Park, Canada

This photograph can be viewed on my website at: Last Light At Maligne Lake