Photo of Poas Volcano Crater, Costa Rica.

How sharp do our photos need to be?

One of the coolest things I learned when I got started with photography was the use of the depth of field scales that came engraved in my lenses. With these I was able to take a picture in which both a friend and the trees in the background looked sharp. For this I just had to make sure the distances to both of them were within the range defined by the depth of field markings in my lens… awesome!

Photo of Lupines growing in the highlands of tropical Costa Rica.
Lupines in the Costa Rican Highlands. Even if the horizon is not perfectly sharp this looks fine as most objects become less-defined at longer distances.

If I were to keep both a nearby subject and a distant mountain sharp I would align the depth of field marks for the f/stop I was using with the infinity mark on the focusing ring and then read the shortest distance at which I could have a closest subject appear sharp. If I needed more depth of field (the range of distances at which things look sharp in the print) I would increase the f/stop as needed… I was on a roll!

Photo of a Tree in the Vara Blanca Highlands, Costa Rica.
Tree in the Vara Blanca Highlands, Costa Rica. Because I used a long lens I couldn’t avoid blurring the trees in the background. However, this provides depth to the image and subject separation.

Modern lenses unfortunately have focusing rings that don’t turn as much as older lenses do and depth of field scales are too small to be useful. Two-ring zoom lenses cannot have them as the scales depend on the focal length… in a word: they are gone. Some people probably have never seen them.

Website depth of field calculators and smart phone apps have tried to save the day and some claim are even better than the depth of field scales in the lenses. Unfortunately, both the calculators and the lens’s scales have been the target of a lot of criticism recently as they seem to fail in delivering the promised sharpness. Some people claim this is because depth of field scales were based on older films and printing papers. Other say they were never good anyway. Still, a lot of photographers bravely defend them… and even Ansel Adams used them.

Photo of a Green Violet-ear hummingbird in San Gerardo de Dota, Costa Rica.
Do you want sharp backgrounds on a telephoto picture? Optics don’t allow it in our cameras. Green Violet-ear hummingbird in San Gerardo de Dota, Costa Rica.

So, who’s right? I have made plenty of landscape images where I get sharpness from my closest subject to infinity so there must be some truth to depth of field calculations. However, I have made other photos that don’t look as good. I have tried hard to understand what is going on and I believe I have an answer.

What I want to do is to give you enough data (images that is) so you can come to your own conclusions about all this. Maybe you will agree with me, maybe not, let’s blog and see. I cannot write long posts (I surely have undiagnosed ADD) and there are many things to cover. If I have sparked your curiosity stay tuned for my next post…

Photo of Tree butresses in Carara National Park, Costa Rica.
Tree butresses in Carara National Park, Costa Rica. A wide angle lens makes it easy to get enough depth of field as long as the composition is what you want.

a peek preview:

Here is a link to a picture you can download to see depth of field scales or hyperfocal distance tables in action. It contains one inch square sections of an 8×10 inch enlargement. I will explain what the jargon means in my next post but, if you already know the stuff, the picture will tell you how to get the depth of field and the image quality you want. Filename is “full-frame-28mmf11-hyperfocal-8×10”

Photos to test hyperfocal distances.
Clicking this image will take you to a Flickr account where you can download the 8×10 inches file.

The first column has crops of Nikon D810 full frame images taken with a 28 mm lens focused at the hyperfocal distance for f/8 and a 0.03 µm confusion circle, then images with the lens stopped down in one f/stop increments. The second column has the lens focused on the distant trees and the same f/stop values. Print in A4 or US Letter sized photo paper (it corresponds to an 8 x 10 inches original picture so each crop is 1×1 in). I processed the photos with Lightroom 5’s default sharpening and settings. Examine from a 13 in distance in good light. On my next post I will offer similar photos for a cropped sensor camera and different final print sizes.

13 thoughts on “How sharp do our photos need to be?”

  1. I’ve had the same experiences. I can usually get the DOF where I need it for those “big” shots. To me, the other side of the coin is controlling the DOF on close in shots where it may be measured in units of less than an inch. Just to add a little more confusion…the answer to your title question is as sharp as I think it should be. As photographers, we are also artists. Some want every blade of grass to be visible and distinct. Others want the effect of blur in some parts of their image.

    Regardless, you raise some very good points to a discussion that is very valuable.

    Liked by 1 person

    1. Thanks for your visit to my Blog and all your kind comments! The crater you see is the active crater from Poas Volcano. A very popular tourist destination in CR. You will surely see it if you come here. Cloudy weather is the only obstacle but there are webcams in this and two other volcanoes. Google “poas volcano webcam”

      Liked by 1 person

      1. You’re welcome 🙂 Interesting, I think I have actually been there as a child (I have family in Costa Rica), the name definitely rings a bell! I will google that now. Hope you have a lovely day in CR!

        Liked by 1 person

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