Commentary, Equipment, Photographic Myths and Platitudes, Technique

Photographic Myths And Platitudes — Diffraction Limited Aperture

October 20, 2017 G Dan Mitchell Leave a comment

It has been a while since I posted an article in my “Photographic Myths And Platitudes” series — so here is a new one! It is a bit different than some of the previous posts in that it is based on something I wrote elsewhere in response to a lengthy (and long-winded!) discussion that suggested hyper-awareness of the so-called diffraction-limited aperture.

What is the diffraction-limited aperture, you ask? It is a real thing — not a myth — though it is sometimes over-emphasized by overzealous techno-photographers. In simple terms, as you stop down a lens its potential maximum resolution declines as a result of diffraction blur. (Keep in mind that other factors affect sharpness, too. Also, this happens to every lens, from the cheapest to the most expensive — it is a universal optical phenomenon.) At some aperture, the increase in blur becomes significant enough, in a technical sense, to be more of a “limitation” on image sharpness than the ability of the sensor to record detail — e.g. the “number of megapixels” of the sensor. A simplistic interpretation of the concept suggests that a photographer should avoid other apertures in order to “get the sharpest image.”

As with many things in photography, it isn’t that clear-cut.

Now on to my original post. It is a bit technical, though I think most photographers should be able to follow it — and I will conclude with some simple, straightforward practical advice. (And here I remind readers that sharpness is not the most important, much less the only important thing in photography. Far from it!)

Sharpness, or at least the perception of sharpness, is a more complex thing than choosing the aperture the provides (to the extent that this can be determined) the highest optical resolution at the sensor plane, measured at either a) the best performing point in the frame, or b) the average across the frame.

(Speaking of “the extent that this can be determined,” I wonder how folks would answer the following question: Which is “sharper,” the image with the best center resolution but slightly lower corner resolution or the image with slightly less center resolution but better overall resolution across the frame?)

While we might consider whether f/16 will be softer than f/8 on some lens/camera combination — it almost certainly will be softer — it isn’t irrelevant to ask: “How much softer, and will this affect my print?” In quite a few cases the difference in maximum resolution in the print will be essentially invisible. In other words, while you will get optimal resolution at some particular aperture, you will actually still get extremely good print resolution at a smaller (or larger) aperture, too.

If there is no particular photographic reason to choose a smaller (or larger!) aperture, you might as well use whatever aperture you think will produce the highest resolution. That best resolution aperture will vary based on the lens you are using, the camera format, and arguably the photo site density of the sensor. To generalize, if you are shooting full frame it will probably be somewhere in the f/5.6-f/8 range with many lenses. (Other things can affect that — for example, what the maximum aperture of the lens is.) On a cropped sensor camera you could, in many cases, use either the same aperture or guess at one stop larger or so — while realizing that there could be resolution downsides to going larger with some lenses. Trade-offs abound! (I’ll spare you the technical discussion of all of the variables. You can think me later.)

But, seriously, if you are calculating the “sharpest” aperture to the closest 1/3-stop for each lens and using that aperture in the field and avoiding others that are slightly different, you probably aren’t really gaining anything significant from your efforts, and you may be sacrificing things that could make your photographs better.

That said, if we know that some mid-range aperture can provide the highest resolution, why use other apertures? And if we do use other apertures, won’t we end up with a softer print? Continue reading Photographic Myths And Platitudes — Diffraction Limited Aperture →

Photographs: Nature, Photographs: Northern California, Photographs: Ocean & Coast

Bluff, Tidal Flats, Tomales Bay

October 20, 2017 G Dan Mitchell Leave a comment

Evening along the shoreline of Tomales Bay

This is another photograph from our very recent visit to areas of California just north of San Francisco. If you follow the news, that description perhaps calls to mind the recent (and current, as I write this) major wildfires burning in California, including the disastrous fire in the Santa Rosa area that killed dozens of people and destroyed thousands of homes and other structures. In fact, we were very close to that area on this trip. We might not have gone at all, except that one of the reasons for going there was to participate in a wedding — and since the wedding went on despite the first, we went. We had planned a few days after that for photography, and we decided to stick to that plan, too.

The effects of the fires were obvious in many ways: signs in shops and elsewhere about people needing a place to stay or raising funds for fire relief, the traffic heading to the coast to try to find relief from the smoke, and the constant presence of that smoke in the air. We ended up doing much less photography than we usually would, but on one day we did manage to make a few photographs. We had driven north up that coast a ways, turning around just north of Jenner where the smoke became quite severe, and we were returning to the area around Point Reyes National Seashore. We arrived alongside upper Tomales Bay, which separates Point Reyes from the rest of California, not long before sunset. Here the smoke thinned a bit, mostly just producing some atmospheric haze, and the scene was quiet and still in the early evening light.

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Photographs: Nature, Photographs: Sierra Nevada

Edge of the Meadow

October 19, 2017 G Dan Mitchell Leave a comment

High elevation trees at the edge of a subalpine meadow, with alpine peaks beyond

As often happens at busy photographic times of the year, I have a set of projects that I’m working on simultaneously right now. Some come from photography I have done as recently as the current week, while other come from work that I did as long as a couple of months ago. Along those lines, I still am working on photographs from our late-August and early September visit to a special Sierra Nevada backcountry location, where a group of us spent more than a week base-camped near a region with an unbelievable wealth of photographic subjects to explore. Today’s photograph comes from that trip.

We were camped for more than a week at a lake just a bit lower in elevation than the location of this photograph. On almost every day we visiting this general area, either focusing on it as the subject or passing by it on our way to other higher places. On this day I had gotten up rather early and explored the area as the first sunlight began to fall on the distant peaks, the meadow, and the trees surrounding it. My recollection is that this was probably one of the last photographs of the morning before I headed back to base-camp, and I’m certain that we were close to the conclusion of our trip. The foreground meadow was typically our main subject here. When we arrived a week from the end of August we were surprised to find it still completely green and filled with wildflowers. The flowers were still there when I made this photograph, but already the late-summer brown meadow color was appearing.

Photographs: Nature, Photographs: Northern California, Photographs: Ocean & Coast

Evening, Wildfire Smoke, Tomales Bay

October 18, 2017 G Dan Mitchell Leave a comment

Wildfire smoke from northern California wildfires colors the evening sky at upper Tomales Bay

In what is perhaps an example of astonishingly bad timing, we were in the region just north of San Francisco for the past few days — near the areas afflicted by the terrible wildfires that have taken lives, destroyed property, and burned over huge swathes of wild land and agricultural areas. The scope of the damage is virtually unprecedented in California, and the events are not yet over as I write this. We were in Petaluma on Friday and most of Saturday, where Patty was to participate in a long-planned wedding of one of her former oboe students. The fires were close enough to Petaluma that breathing masks were provided to those attending the wedding, and at times ash fell from the sky like very light snow flurries.

On Saturday we moved closer to Point Reyes National Seashore. Our original plan had been to spend a couple of days photographing there, but the conditions were not conducive to photography for the most part. We visited the Seashore on Sunday, but the smoke and the naturally brown October conditions, combined with a complete lack of moody for or other clouds left us a bit uninspired. We found a few things to photograph, but we finally decided to just drive north up that coast a ways. We got just past Jenner, where the smoke become even thicker — and we turned around. The smoke was not the only evidence of the fires. Signs were up everywhere — restaurants and similar places — with announcements of fund-raisers, requests for donation, notes from people looking for a place to stay. It was also clear the folks from inland had headed out toward the ocean to try to escape the fires. We left Jenner and headed back toward our lodgings in the Point Reyes area, and just at sunset we arrived at upper Tomales Bay. It was quiet and still as we stopped at a high point from which we could look out over the bay and north toward its mouth. It was still smokey, but here the smoke merely softened the features of the landscape and added color to the sky and the reflecting water.

G Dan Mitchell Photography

Photographic Myths And Platitudes — Diffraction Limited Aperture

Bluff, Tidal Flats, Tomales Bay

Edge of the Meadow

Evening, Wildfire Smoke, Tomales Bay

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