How Many Pixels Do I Need? Logic And Reality Versus Emotion

Split Rail Fence and Buttercups (click to enlarge)
Fujifilm X-H1; 16-55mm f/2.8 lens @ 35mm; 1/170th sec. @ f/11; ISO 200

The pixel wars may largely be over in the digital photography industry as we now have cameras available at affordable prices (that, of course, is subjective) that range all the way up to 50mp.  Despite that, the pixel wars seem to continue inside my mind.  Even though I logically know how many pixels I need to do everything photographic I need to accomplish, my brain sends conflicting emotional signals telling me I need more!  Funny how things like this work.  

The old logic versus emotion conflict still rages and shouldn't be ignored.  I believe that even though we know how many pixels we need we are selling ourselves short if we don't also include our emotional needs.  We can use a digital camera with a sensor that has an adequate number of pixels but be unsatisfied with our photography because that camera and sensor just doesn't satisfy our emotional needs and that is a real effect.

The reality for me is that I do very little printing anymore.  Almost all of the prints I have made in the past few years have been 8" X 10" (20cm X 25cm) or smaller.  I've made a few 11" X 14" (28cm X 35cm) prints, but very few.  On occasion, when I've needed a larger print for a large wall display or one that I have sold, I've sent the files off to a commercial photography printer to print them for me.  Almost all of my photography these days is displayed on this blog, on Instagram or on my website.  So, how many pixels, in reality do I need?

The largest web images I export from Lightroom Classic CC are 2732 pixels on the long edge.  I chose that because that is the long side screen dimension of my 12.9" iPad Pro.  I wanted to be able to see my images without "up scaling" them on that device.  Looking at my images on that device is part of my editing process.  I can see what they will look like as others may see them.  On other web viewing devices, the images are reduced in size to fit the screen resolution.  For web use, 2732 is as large as I will display.  Using a 2:3 full frame or APS-C image ratio, that comes out to a 2732 X 1821 pixel ratio.  That also results in just under 5mp.  If I only displayed digitally and didn't print, theoretically a 5mp camera would serve me pretty well.  That's not a very big sensor when you see it in writing.

For prints, for argument's sake, I'll assume that 11" X 14" is the largest prints I would normally make.  I also think 300 dpi is a nice compromise resolution to create prints with sufficient resolution and detail that, under non-magnifying glass conditions (normal viewing distances), you won't be able to notice any lack of fine detail.  That equates to 3300 X 4200 pixels or a 13.8mp sensor.  It seems that for full image 11" X 14" prints, most any sensor out there will get the job done.

What about cropping?  Sometimes you have to crop.  I prefer not to crop but sometimes conditions are in place that you can't get close enough or you don't have a lens long enough which forces you to crop to achieve the best composition.  In those cases you may have to crop your image.  Also, when performing edits such as straightening verticals, you will lose some image area on each side.  Let's say we would never think about cropping more than 30%, and I'm not sure I would ever crop that much for anything more than web use.  I have posted 100% crops but I really try to avoid that like the plague.

Now considering cropping, let's add 30% to our figures.  For web use, losing 30% of the image area but still wanting to send out an image with the long side at 2732 pixels, I now need 3540 pixels on the long side in the original image.  Again, using a 2:3 ratio, that would be 3540 X 2360 pixels on a sensor, or 8.3mp instead of 5mp.  That is basically 4K for you video folks.  For prints, keeping the same ability to crop up to 30% and making the same assumptions as in the paragraph above, I would now need a sensor 5460 X 4290 or 23.4mp.

At the end of the day, if I were only posting images on the web, I would need only an 8mp sensor.  If printing an 11" X 14" print with the ability to crop up to 30% of my original image area, I would need about a 24mp camera.  Intuitively, many times in the past, I've written and said that 24mp is my sweet spot and now, when doing the math, it turns out that is right on the nose.  Any sensor that has more pixels than that are not needed for the kinds of photography I do and how I show my images.  Everything sensor giving more pixels than that is most likely waste.

But...

What if I want to send off a file for a much larger print?  How many pixels do I need to make, say, a 16" X 24" (40cm X 61cm) print?  How about larger than that?  For my large prints, I have mainly used mpix.  I have found their work excellent and I have both enlargements made as well as enlargements matted and framed.  I've never had a bad experience, they are fast and their prices are reasonable.  (No, I'm not sponsored by them nor do I receive anything from them and they did not ask me for an endorsement.  Why would they?  I just pass on to you what I have found that has worked well for me.)

"mpix Photo Lab" file size requirements
Left column is optimal file
Right column is minimum file size

I went to mpix's site to find out what size files they need to make various size enlargements.  The illustration on the right lists the "optimal" number and the "minimum" number of pixels required for prints.  You an find the chart on their site here.  I looked but couldn't locate the file resolution they want, but it seems to me they want 300 dpi JPEGs but that may have changed over time.

There is quite a difference between the two columns of numbers. Of course, one would want to submit "optimal" files if you have them.  The "minimum" files sizes seem pretty small but I would suspect, however, being that they are a highly successful professional photographic printing company, that the "minimum" number of pixels for any given size would produce a good print, otherwise customers would be dissatisfied and would not continue to do business with them.  In other words, they wouldn't publish numbers that result in poor enlargements.  Frankly, I'm kind of amazed at how small files seem to be able to produce large prints, according to their published information.

For example, for a 16" X 24" print (40cm X 61cm), the "minimum" sensor size needed to make such a print is 3.8mp!  That sounds crazy as the "optimal" size sensor for an 16" X 24" print is a 24mp sensor.  That still sounds too low to me but they seem to know what they are doing, as I said, they are a highly respected company.  They must have some magic fairy dust to sprinkle on the files or they have great file upscaling algorithms.

I certainly don't know your types of photography and how you display your images, but you might want to do your own math and figure out just what you need and what you don't need.  No need to spend money buying a camera with a sensor much larger than you would need when you could put that money to better use and buy excellent lenses that will eek out every bit of quality your sensor can produce.

The one thing I have not yet addressed is that emotional part of the equation.  We tend to think "more is better" and many times it is.  In terms of digital photography, we want to think we need more pixels than we normally need for those times that are the exceptions rather than the rule when it comes to printing or display.  We want to be assured we have every situation covered and covered adequately, just in case.  We believe that just the time we want to go bigger with a prized image, we can't.  The result is that we over-buy and over-engineer "just to be sure."  But that is human nature and thoroughness.  And, even though it may not make sense logically or mathematically, our brains tell us it makes sense emotionally.

When you are trying to figure out what you need, how much you need and analyze how you work, my advice is to calculate the emotional part of the equation as well as the mathematical part.  If you don't, you may have a camera with a logically adequate sensor but you may not be emotionally satisfied and, in the end,  that can affect your work.

Join me over at Instagram @dennisamook or my website, www.dennismook.com. 

Thanks for looking. Enjoy! 

Dennis A. Mook 

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