Question of the day

A reminder that I welcome questions on photography. From pros or from beginners, or from anyone in between. I shall answer (it may be a while, but I promise I will).

Here’s a recent question, answered belatedy:

What do you look for when you are judging the quality of an image?

Dpreview has recently published some sample images from the “entry level” Leica X1. See

I’d like to hear your opinion on how to evaluate the quality of the samples relative to other cameras. One good thing is that Dpreview keep all their samples on their web site going back years. And often they are of similar subjects – e.g. Tower Bridge, London.

Mmm. Tough one.

When I look at quality I compare subject and composition, moment, and light. But that is not what you mean, is it? You mean to compare cameras. Tough, because it is difficult to compare apples with oranges, and since different cameras address different needs, they are not always directly comparable.

And yes, there it starts with using the same subject. DPreview has Tower Bridge and the British museum as frequent subjects. Here’s my version:

Fortunately, DPreview also have their standard studio setup (with the Martini bottle) designed to test the important camera quality items.

I think for me these important items include:

  • High ISO performance
  • Noise, especially in shadow areas
  • Dynamic range: how many stops from black to white?
  • Sharpness
  • Colour saturation
  • Lack of moiré
  • Long exposure capabilities
  • Vignetting (lack thereof being good)

Note that “RAW shows the camera’s actual capabilities, while JPG shows that plus the in-camera processing capabilities”. One of those can be good while the other can be less so, or both can be good or both can be less stellar.

Does that help, at all?

0 thoughts on “Question of the day

  1. Yes, I was wondering how you’d decide whether to buy a new camera based on marketing claims of better image quality. You’ve got some of the best cameras currently made with the EOS-1 and the 7. Is there anything about the quality of the images you obtain that dissatisfies you? What would persuade you to, for example, move to a different manufacturer for your work?

    I realise it is not just the camera – it is the whole system and especially the lenses. I bet if I put the original kit lens from the EOS-300D (EF-S 17-55mm, F4-5.6 non-IS) on a 7D I would not be happy with the results. Likewise if I put a L lens on my EOS-300D I might think I’d bought a new camera.

    I think some of your criteria above are lens-related: sharpness and vignetting.

    I believe Phil Askey and his colleagues at DPreview pioneered the scientific evaluation and comparison of digital cameras. Some complain at their “pixel peeping” approach but it seems like the best way to make objective comparisons. I agree it makes most sense for high quality cameras. The results for P&S cameras will always be disappointing and their results are often painful to observe.

  2. Actually, sharpness and vignetting are ALSO Camera-related. The anti-moire filter introduces blur, and the sensor’s design can encourage vignetting.

    Phil is doing what a lab would do, and I agree, it’s the only way to be objective and repeatable in your evaluations.

    Weighting of the variables, however, is up to the individual. For me, sharpness and noise are the big ones.

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