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Big Prints from a 60D?

By Dwight Arthur, 2011/04/04

Q. Is it possible to create high-quality, really large prints like 4' x 6' from a camera like a Canon 60D, which has an 18 megapixel sensor?

A. This is not a question for which there is a definitive answer because image quality is something that is relative, and there is a lot more that determines image quality than merely the resolution of your camera!

First of all, one has to consider how close your audience will be to the print. There is a big difference between viewing a print held in your hands and something on a wall, especially when you are standing several metres away. If you are still 18 inches away when viewing very large prints than they certainly won't look great,

but when viewed from a more typical distance of several metres then any image that appears very sharp as 12x18 inch print held in your hands should also look very sharp as a large wall-mounted print. I would have no hesitation in saying that IF all other criteria for image quality is met that an 18 megapixel image from a DSLR can produce very good 4' x 6' prints when viewed from a reasonable distance. I have created very pleasing prints of this size from an 11 megapixel camera so using an 18 megapixel camera is going to be potentially even better.

"You can use a camera capable of potentially outstanding results but still create images of mediocre image quality! A great photograph is usually the cumulative outcome of many small things done really well."

In order to ensure outstanding image quality in a large print there is going to have to be a lot of of other things you'll have to consider...image qualtiy is not just about megapixels! You can use a camera capable of potentially outstanding results but still create images of mediocre appearance! It happens all the time. A great photograph is usually the cumulative outcome of many small things done really well. Some of the other critical image quality issues that must also be addressed for success when super-sizing your prints are:

- an excellent lens (they are not all created equal and there can be a visible difference in outcome with various lenses of the same focal length).

- good technique, including a good choice of aperture that achieves high resolution while eliminating other lens defects like chromatic aberration and diffraction (middle of the range apertures are best for image quality IF they deliver adequate depth of field. You will find significant loss of resolution and resulting detail when using the largest and smallest aperture settings.

- other technical issues, such as a stable camera (a solid tripod properly set up, and preferably using a cable release and mirror lockup), very careful focus (use magnified live view and manual focus) and of course use of ISO 100 rather than higher settings.

- proper post-production sharpening for large prints is also key to delivering the best detail but is too involved to share in this response. In general terms, over sharpening through use of Unsharp Masking with too wide a Radius or too high an Amount set will create far less pleasing results than more moderate settings, especially if the print will be viewed from relatively close distances.

- careful noise reduction technique: too heavy-handed an application of noise reduction can really rob a print of textural detail.

Proper resizing technique is a another critical step in the big print process.

When creating really large distplay prints you will certainly NOT be generating them at 300 dpi as you would for smaller prints! If you enable resampling when resizing the image to a 4' x 6' print size and set the resolution to 300 ppi all you will be doing is taking the original pixel grid and redistributing the detail contained therein to about 4 times as many pixels. The file will balloon to a massive 890 megabytes and there will be no increase in detail at all. That is because the potential detail of a photograph is determined by the available pixels at the point of creation (as determined by by the resolution of the camera's imaging chip). When it comes to resizing with resampling turned on the bottom line is that it is unproductive: you can't create more detail after the image is originally captured. As a matter of fact, the image will appear slightly less sharp if anything when resampling because of the resulting re-interpolation of the data.

"The detail of a photograph is determined by the available pixels at the point of creation, as determined by the resolution of the camera's imaging chip. Adding pixels when resizing won't add detail to the image."

If, on the other hand, when you set the print size to 4' x 6' you do it without resampling the image (turn resample off in the resize dialogue) the native resolution of your file (from an 18 megapixel camera, uncropped) will create an image that is about 72 pixels per inch and the saved file size will remain exactly the same. While for a small print viewed at close distance 72 ppi is unacceptable, for a really big print it is just fine, and merely adding more pixels won't add detail anyway. If a 72 ppi print is viewed from 18 inches away you admittedly may be able to see individual pixels if you look hard enough, especially in the form of aliasing (stair-casing effect of pixels) on sharp diagonal lines, but that is seldom how such prints are viewed. In the real world you will be farther away, and I can assure you that from there they will look great!

I do a lot of very large prints, some bigger than 4' x 6', and I have proven that this simple resizing works great, despite the fact that you will definitely find someone who will tell you otherwise if you look on the web for advice!

If you feel you really must reduce the visibility of individual pixels to reduce the aliasing effect there is a two-step solution that doesn't make the file size too large: first you precisely double the resolution when resampling (Set Resample on and set the print size to 200% and apply the resize. When doing this first resizing with resample on, it helps a bit if you set the resample method to "best for enlarging" in the dialogue. Next you will turn Resample off and set the print size to the desired 4' x 6' and apply resizing again to complete the process. This resizing method prevents fractional sharing of pixel data that results in excessive blurring so you won't lose as much detail. You will find that the aliasing will be less noticeable, and your file size won't be so ridiculously large, although it will still be 4x the size of the original. I must say that I don't bother doing this however. I just resize with resample off and let the resolution float to whatever value that results when the desired print size is set. Sometimes this will result in resolution values as low as 60 ppi but all I ever get is compliments about how great these huge prints look, so it must work pretty well :-)

One final point on going big with prints: the impression of detail also varies according to the subject of the photograph. Generally speaking a landscape benefits more from added detail than a photograph of something like a still life, especially one of small objects. It may be only a psychological effect that when we see a small object enlarged we are impressed with the details we can see that normally we can't, but it is a very real impression nevertheless. Photos of small things look amazing when enlarged to very big print sizes!

As you can now see, high quality big prints are certainly possible with an 18 megapixel camera but there's a lot more to getting outstanding big prints than just this one factor!

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