Category Archives: Equipment

Commentary, Equipment

Why Your 21MP File “Looks Softer” Than Your 12MP File at 100% Magnification

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(Note: 21MP cameras were state-of-the-art when I wrote this. While that is no longer the case, the explanation of the concept still applies to comparisons between more recent higher MP cameras cameras with differing sensor resolutions. And, years later, camera reviewers are still making the mistake that I address here.)

A frequent photography discussion forum meme is that “this old camera with fewer photosites produces sharper images than this newer camera with more photosites. In fact, I have carefully inspected 100% crops from both and the evidence is clear!”

Not so fast.

Let’s imagine that the comparison is being made between the full-frame 12MP Canon 5D and the full-frame 21MP Canon 5D2, both of which I own and use. If you put the same lens on both cameras, set the lens to the same aperture, and point both cameras at the same subject, the lens will project exactly the same image onto the sensors of both. Let’s say that you do this under controlled conditions, and you decide to compare the two captures to see if the 21MP camera is really sharper than the 12MP camera.

You want to compare closely, so you display both images as “100% magnification crops” – portions of the image that show each individual pixel from the original photograph as an individual pixel on your computer monitor. You display the two images side by side and, squinting closely and looking back and forth between the two, you notice that the 21MP original is certainly no sharper than the 12MP original and that the 21MP image actually looks a bit less sharp! You decide that a) higher MP cameras are less sharp than lower MP cameras (you have the evidence!), and/or b) the camera companies are pulling a fast one on us.

You are actually wrong. Dead wrong.

When gazing too long and too intently at a computer screen, it is easy to forget that the real world is not always represented accurately on the screen. In this case, the error is a result of viewing on a computer screen rather than making more realistic comparisons, for example between two prints of equal size. With the screen image comparison, you might overlook a fact that explains why the sharper (or at least equally sharp) camera appears to be less sharp. A look at the above  illustration will help.

The image includes two copies of a full-frame photograph. Think of the one on the left as representing the photograph made on a 12 MP camera (like the 5D) and the one on the right as representing a 21MP camera (like the 5D2). The original 5D image would be 2912 pixels wide, while the original 5D2 image would be 3744 pixels wide. The full-color area of each image represents the part of the original image that would fill the screen of a 1280 x 1024 monitor when the originals are viewed at 100% magnification.

The critical point illustrated here is that the 1280 x 1024 “slice” of the 21MP image shows a considerably smaller portion of the overall image, and in order to fill the same size screen it will have to be magnified more than the image from the 12MP camera. If the two images are equally sharp to begin with, the one that has to be magnified more to fill the screen will lose more of its original resolution because you are looking more closely at a smaller portion of the image.

In the end, if you were to make two prints of the same dimension from the two original full images, the higher MP original would look at least as sharp as the lower MP original, and if you use good lenses and good technique (and print large enough that it makes a difference) the higher MP version has the potential to resolve more detail.

Some related points

A few related notions about sharpness and megapixel resolution also come up from time to time, and those who believe in them can be quite stubborn about their misunderstandings. Here are a couple:

  • Claim: When you move to a higher MP sensor your photos will be more susceptible to motion blur.False. This is not the case at all. If you make otherwise identical photographs with a low MP full frame (or other format) digital camera and a higher MP camera using the same format, prints of the same size from both sources will have exactly the same amount of motion blur. (Technically, the higher MP camera will provide a more accurate image of the blur, but that doesn’t change how much blur there is.) In both cases the blur covers the same percentage of frame width. And, if you are tempted to check 100% magnification crops to prove me wrong, don’t forget what we saw above about looking more closely at a smaller area with the higher MP example. (The good news for the higher MP sensor is that when there is less motion blur it has the potential to produce an even higher resolution image of the subject.)
  • Claim: Because the diffraction-limited aperture is larger when you work with higher resolution sensors, you’ll have more blur at smaller apertures with the higher MP system.False. You’ll have exactly the same amount of diffraction at every aperture. Diffraction is an optical phenomenon that is not affected by the sensor. Once again, if you make prints at some size from otherwise identical frames from a higher and lower resolution system, at every aperture diffraction will affect both the same way. And, again, while the higher MP system is never worse, if you use a very good lens and open up a bit you may get an even sharper image from the higher MP system.

In every case, either the two systems perform the same or the higher MP system is better. There is no situation in which the lower MP system will produce a sharper print at a given size, and there are some in which the higher MP system will make a sharper print… or allow one to make a larger print with the same resolution.

(See related post: “Myth: Diffraction and Motion Blur Worsen With More Megapixels”)

G Dan Mitchell is a California photographer and visual opportunist. His book, “California’s Fall Color: A Photographer’s Guide to Autumn in the Sierra” is available from Heyday Books and Amazon.
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Commentary, Equipment, Technique, Tests

“My Photos Are Soft!”

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So, you have a camera or lens that you think is not as sharp as it should be. If you are already expert at these things, what follows is not for you – you already know how to analyze the problem, you can anticipate possible causes, and you know some of the pitfalls of looking at the issue in unrealistic ways. But if you aren’t certain about how to deal with the issue, perhaps the following might help… so feel free to read on.

Perhaps you just got a new lens or a new camera and you don’t think it is performing as you expected. Or perhaps you have long suspected a problem with your equipment. On the other hand, maybe some gear that you have used with confidence for a while seems to not work as well as you recall it working in the past. It can be tempting to blame the equipment – and in some cases you may be correct – but it is a very good idea to first try to analyze and understand the problem and look for other possible causes… and solutions.

It is critical that you try to control the variables that might give rise to the issue, and then to try to a) determine if the problem is real, and b) figure out specifically what might be the cause. The range of possible causes is larger than you might imagine: problems with the camera’s autofocus (AF) system, an out of adjustment or “weak” lens, less than optimal choice of lens settings, issues with camera stability, insufficient care with the use of AF, using the wrong AF settings, aperture choices, shutter speed choices, subject motion, and more. While a real equipment problem is a possibility, it is probably at least as likely that the problem lies elsewhere. Fortunately there are ways to wade through this minefield and develop some rational understanding of what is going on.

What follows is a sort of ad hoc description of how I might approach this. It is not meant to be the only way to deal with such issues, it leaves out some possibilities, and the sequence could be changed around in some ways. Continue reading “My Photos Are Soft!” →

Commentary, Equipment, Technique

Backpacking and Photography – a Quick Link

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I often field questions about doing photography while backpacking – what equipment to take, what to not take, how to carry it all, and so forth. I’ve been a Sierra Nevada backpacker for a long (really long!) time, and I do a fair amount of my photography while on the trail for periods ranging from a single day up to a couple of weeks.

This is time of year when many of us find our thoughts turning to the coming back-country season… and how to incorporate photography into that experience. I’m not going to go into all of the details in this short post… but I have previously posted about my own backpacking photo gear, and I’m sharing that link again for those who might be interested.

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Text, photographs, and other media are © Copyright G Dan Mitchell (or others when indicated) and are not in the public domain and may not be used on websites, blogs, or in other media without advance permission from G Dan Mitchell.

Commentary, Equipment, Ideas

Photography and Gear Fetishes (Another Adapted Forum Post)

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Earlier this week I dropped in on a photography forum in which the OP (original poster) suggested that the causal correlation between buying Really Expensive Gear and producing better photographs was weak. Oh, yeah!

Here is a slightly adapted version of my contribution to that discussion:

I’ve thought quite a bit about why so many “photography enthusiasts” seem to be much more interested in acquiring photography gear than in making photographs. Reasons might include:

1. Equipment is necessary in order to make photographs, so acquiring some is not unimportant.
2. Because it is, frankly, easier to write about gear in definitive (or seemingly definitive) ways than to write competently about photographs, there is much more written about gear – and newbies should be forgiven for having a false impression that the gear one has is more important than the photographs one makes.
3. Almost all of us do find the equipment fascinating to some extent. Some grow past this, but for some it ends up being more about possessing expensive and supposedly high-end stuff than anything else. (Photography is not the only area where this occurs.)
4. Because people more often encounter photographers when they are operating cameras than when they are exhibiting photographs, they associate the gear with the activity more than they associate photographs with it.
5. Some want to look like (what they imagine) professional photographers (look like).
6. Some are told, before they have enough experience to question it, that they must have “the best” gear if they are going to make photographs. I’ve actually seen rank beginners struggling with $6000 bodies and sets of L primes or big white telephotos… for their family vacations.
7. Some love to shop.

[The OP’s] notion that the causal correlation between expensive gear and photographic skill or quality is weak is one that I would agree with.

I think that a “cure” for the counter-productive obsession with gear at the expense of photographs may be to do everything in your power to focus on photographs – not photography, not cameras, not lenses, etc. If you are not or do not become passionate about producing photographs, then you might want to consider a different hobby. :-)

G Dan Mitchell Photography | Flickr | Twitter (follow me) | Facebook (“Like” my page) | LinkedIn | Email
Text, photographs, and other media are © Copyright G Dan Mitchell (or others when indicated) and are not in the public domain and may not be used on websites, blogs, or in other media without advance permission from G Dan Mitchell.