Tag Archives: technical

Commentary, Morning Musings

Misplaced Focus (Morning Musings 12/3/14)

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Family Portrait
Family Portrait

From time to time I adapt things that I wrote elsewhere and re-share them on the blog. The following is something I contributed to a discussion about a question from a newish photographer who wondered how important it would be to upgrade his camera. 

I’m all for better image quality — which contemporary cameras, software, and printing processes provide in spades. And there is no question that, all else being equal, a photograph captured on a larger film or sensor format can potentially resolve more detail, and may improve other image parameters including dynamic range and noise.

As they say, “So stipulated.”

But the question (which was about choosing a sensor format) deserves a more nuanced and contextual answer than that. Fortunately, the most accurate and useful answer involves quite a bit of that nuance. I think it really comes down to something like, “Will replacing my cropped sensor camera with a full frame camera make my photographs look better?”. The best answer begins with, “It depends.”

As to the question (which also came up in the original discussion) of what is important in a photograph, image sharpness is not unimportant in many cases. (Though there certainly are photographs whose “goodness” is perhaps at least partially because they are blurred — softness and blur are not always things to be avoided.)

I think the issue in photography discussions is frequently about the balance among issues that affect the quality and effectiveness of a photograph. Here, it is not uncommon for some folks to exhibit a misplaced focus on the technical stuff, accompanied by insufficient attention to other things that are more important to their success as photographers. Continue reading Misplaced Focus (Morning Musings 12/3/14) →

Commentary, Equipment, Post-processing Workflow, Technique

Post-Processing: A Shadow Recovery Example

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(In another forum someone asked a question – actually, more like posed a challenge – related to how much usable detail and quality could be extracted from a raw file that contained areas of very low luminosity, as could happen with a badly underexposed image or with an image of a scene with a very large dynamic range. Since I went to the work of responding and illustrating my response, I figured that I might as well share it here, too. With minor revisions, here it is.)

First, I actually have a “real” version of this photograph in which highlights were slightly blown, but which I preferred to use since I could bring them back in post and get a bit more shadow detail to start with. (It looks a bit bright to me as an on-screen jpg, but it makes a fine print.) That photograph ended up looking like this:

Kolob Canyon, Morning - Morning light slants over the top of sandstone cliffs above early autumn foliage in Kolob Canyon, Zion National Park
Morning light slants over the top of sandstone cliffs above early autumn foliage in Kolob Canyon, Zion National Park

This photograph and the other I’ll move to below were both shot from a tripod with a Canon EOS 5D Mark II at ISO 100 using the Canon EF 24-105mm f/4L IS at f/16. While the “keeper” used for the photograph above had a 1/4 second exposure, the example I’ll use below was shot at 1/30 second.

The exposure challenge in this scene was the very large dynamic range between the bright spot of sky at the head of the canyon and the much darker colorful foliage in relatively deep shadow in the foreground. Exposing for optimal quality in the foreground would completely blow out the sky, while exposing for the sky would necessarily grossly underexpose the foreground.

I originally thought that I might like to have four bracketed exposures in case that would let me produce a better final image via layer blending, but it turned out to be unnecessary and the final image (as shown above) has a single source file with no blending. However, this means that I still happen to have one very badly underexposed (by three stops) version at 1/30 second which I’ll use here as the starting point for what I plan to illustrate in this post. Follow along with me and see what I can do with the very underexposed version of the file… Continue reading Post-Processing: A Shadow Recovery Example →

Equipment, Technique

Some Thoughts on Aperture and DOF and Related Issues

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(This post is slightly adapted from something I recently posted in a photography forum in which hyperfocal distance, “DOF calculation” software, and related issues were under discussion.)

Shooting as a way to learn to understand how things like depth of field or “hyperfocal distance” work is a great idea – it is perhaps the best way to understand these concepts. I firmly believe that it is better than relying on tools such as software DOF (“depth of field”) calculators or tables. Fortunately, it is easy to do some basic experiments related to aperture and DOF and the so-called hyperfocal distance.

(The term hyperfocal distance can be interpreted in a couple of ways. In photography, this is often thought of as the distance at which you might focus in order to place objects at different distances in focus. If there is an object that is 15 feet from the camera and there are important subjects at infinity, the hyperfocal distance lies beyond the object that is 15 feet away and closer than the far away objects that might be in focus with the lens set to “infinity.”)

To find out about the effect of aperture on DOF, try the following:

  1. Put the camera on a tripod and compose some reasonable test image that includes subjects at various distances from the camera position, with a primary subject somewhere between the closest and the furthest.
  2. Focus on your primary subject within the scene.
  3. Shoot a series of images at apertures ranging from the largest to perhaps f/16 – shoot at f/1.4, f/2, f/2.8, etc. You might want to go as far as f/22 on full frame.*
  4. If you want to be a bit more methodical, you can use your DOF tables/software to “calculate” your hyperfocal distance, focus there, and repeat the process – but, frankly, I wouldn’t bother.
  5. Spend some time – likely well under an hour – looking over the results on your computer. If possible, make a few small prints to confirm the relevance (or not) of what you observe on the screen.

Another great way to understand the effect of aperture on the depth of field in your shot is to shoot in live view mode on your DSLR. Here you can press the DOF preview button, zoom in the live view display to 5x or 10x magnification, and pan around the magnified image on the rear display to see a very good approximation of the effect of your aperture choice on elements of the scene at various distances from the camera.

SIMPLIFICATION: A SECRET

Let me share a little secret. From reading some photography forum posts, you might get the idea that lots of photographers are going around making careful and technical calculations of precise hyperfocal distance and DOF and all the rest and then making exactingly accurate choices about aperture for each shot. In general, it doesn’t work that way in the real world, where photographers often tend to select aperture in basically three ways:

  1. In a shot where the subject doesn’t have a lot of depth and DOF isn’t really an issue, we tend to shoot at some default aperture that we believe is more or less optimal for overall resolution, corner resolution, and perhaps vignetting. On full frame, this might frequently be roughly f/8, though there are reasons to vary from that a bit sometimes.
  2. When working a subject on which we want very large DOF, we tend to go straight to the smallest aperture that we feel will produce large DOF and very good resolution. For me, this is typically f/16 on full frame, it might be no smaller than f/11 on cropped sensor cameras. There are situations in which I might use a smaller aperture, but they are very rare and will involve acceptance of some tradeoffs.
  3. When faced with a shot in which we want very narrow DOF, we tend to open up as much as we think we can, perhaps tending toward the largest aperture on the lens we are using. There are some additional factors to consider here, but I’ll leave them out for now in the spirit of simplifying.

So, a simple generalized approach:

  • Shoot at some middle-of-the-road aperture when DOF isn’t a major concern.
  • Shoot at the smallest acceptable aperture when you want large DOF – f/16 on full-frame or f/8-f/11 on crop.
  • Open way up when you want to minimize DOF.

This approach works in a wide range of real-world photographic situations, and it is especially useful to begin with it when you have to work quickly. There will be situations in which these are simply starting points, and you’ll need to make some modifications – for example, in very low light you might not be able to use that very small aperture if you are shooting hand-held, or your largest aperture might produce DOF that is too narrow for some subjects, and so on. But starting with this simple basic concept, using live view DOF preview when appropriate, and learning from experience will likely move you a lot further along on the road towards understanding and making effective use of aperture/DOF than trying to rely on some DOF calculator. (Depite their appearance of accuracy, these calculators depend on a bunch of assumptions that may not match up with your photography.)

* You can stop down further on cameras with larger sensors before you run into issues with diffraction blur, a softening of the overall image that occurs with the smallest apertures. To generalize, while you can stop down to roughly f/16 on a full frame and still produce very sharp images, you might want to avoid such a small aperture on your cropped sensor DSLR, perhaps avoiding anything smaller than about f/11… and you might want to be a bit cautious about using f/11.

© Copyright 2012 G Dan Mitchell – all rights reserved.

G Dan Mitchell is a California photographer whose subjects include the Pacific coast, redwood forests, central California oak/grasslands, the Sierra Nevada, California deserts, urban landscapes, night photography, and more.
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Commentary, Ideas, Photography and Music

Music and Photography: Technique and Interpretation

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(I accidentally published this draft post earlier today while doing some site maintenance. Shortly afterwards a friend contacted me to say that he had composed a response… only to find that the article had disappeared when he finished writing. My apology! Even though the article is not perhaps final – for example, the title is not quite right for the content – I have resurrected it. I intend this to be part of a longer series of posts.)

There have been and are quite a few photographers who also have backgrounds in music, and in quite a few cases these individuals could have had – or actually did! – have careers in both fields. The story of Ansel Adams supposedly making a choice between being a photographer or a pianist is well-known, and there are plenty of other examples. I don’t presume to put myself in the same category as Adams, but I’m also one of these people.

When I talk with other photographers who either share this dual background or who are aware of the number of other photographers who do, the conversation sometimes turns to the question of why this is the case. What points of contact are there between the practice of music and the practice of photography? The differences seem to me to be quite obvious. Clearly one medium deals primarily with sound and the other with visual images. In addition – and I think this is even more significant – music uses the element of time in a way that photography rarely can.  Photographers almost never tell you in what order you must view photographs – though they may suggest – nor do they insist that you move on to the next image after some specified interval of time. While the photographer may intend for you to follow a particular path through some images, there is no way to ensure that you do… and you probably don’t! But the musical composer relies completely on controlling the flow of events in time. It is emphatically not OK to switch sections of a piece and so forth.

So, what is similar?

I think that there are several points of contact between music and photography. I have no illusion that I can say everything there is to say about this in one post, so let me start with a single very basic idea having to do with the relationship between technique and interpretation or expression. Continue reading Music and Photography: Technique and Interpretation →