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When all you had was your mobile...

Discussion in 'Smartphone photography' started by plugsnpixels, Dec 29, 2016.

  1. Chester AP

    Chester AP Well-Known Member

    I have seen this before, and done more investigation myself on some other websites. The problem when trying to be helpful, is to judge how much (and what kind of) detail should be offered. I try to offer practical advice based on my own experience, and sometimes refer to a page from the 'cambridge in colour' because I (and some other Forum members) have found it helpful.

    For example, in practical use a certain lens aperture will appear to give more depth of field on a small sensor camera body than on a body with a larger sensor. But to be strictly accurate the depth of field for a given aperture is the same whatever the sensor size as long as the angle of view of the lens is the same. So, for example, F8 on a 34 mm lens on a camera body with half-frame (APS-C) sensor should give the same depth of field as a 50 mm lens at F8 on a 'full frame' camera body, but it's simpler to follow the 'rule' that an aperture on a half-frame (APS-C) give the about the same depth of field as one stop smaller on a full frame and not worry about the difference between the lenses used on the two camera bodies. The web page below has a calculator that shows a depth of field for a 50 mm lens focused at 5 metres on a full frame body at F8 to be 6.82 metres, and for a 34 mm (equivalent to 50 mm on a half-frame (APS-C)) at F 5.6 to be 6.82 metres also. When I first moved from a full frame 35 mm film camera to a half frame (APS-C) DSLR I did not know about this, and would have found it helpful.

    This also explains why smartphones can have such a large depth of field with a lens aperture of F1.8 or similar - the minute sensors require a very short focal length lens and the large depth of field is the result, which is probably what most users want even if they don't understand what it is.

    John Fantastic likes this.
  2. Chester AP

    Chester AP Well-Known Member

    I have also found this on the AP website, comparing aperture/depth of field and diffraction 'blurring' on full frame and micro four thirds sensors in 2016.


    This is from the last paragraph of the article, which matches my observation above about F5.6 on half-frame (APS-C) having the same depth of field as F8 on full fame as long as the smaller sensor is used with a lens equivalent to (having the same angle of view) as the lens used on the full frame. So if you buy a camera body with a 'one inch' sensor and like to use F 8 or F 11 because you expect a large depth of field, don't expect sharp images that will look good as large prints.

    It’s therefore simple to establish a set of apertures equivalent to f/8 on full frame for the most commonly used sensor sizes. For APS-C (1.5x crop) it’s f/5.6; for micro four thirds (2x crop) it’s f/4; and for 1in (2.7x crop) it’s f/3. Equally, if we consider f/16 to be the smallest aperture we’re happy to use on full frame before diffraction blurring becomes completely intolerable, we should limit ourselves to f/11 on APS-C, f/8 on Micro Four Thirds and f/6.3 on 1-inch sensor cameras.
  3. PeteRob

    PeteRob Well-Known Member

    I’d forgotten that AP article, which makes the role of the physical aperture clear. “Sharp” is also a relative term that depends on the viewing distance so a large print, that may be “less sharp” when examined close up, can be acceptable when viewed at a comfortable distance. It doesn’t automatically follow that an image taken at F8 and F11 taken with a compact won’t look good as a large print. Just don’t approach with a magnifying glass.
  4. Chester AP

    Chester AP Well-Known Member

    I've commented before on other threads about large prints and 'sharpness', and the obsession with 'upgrading' at great cost to new camera bodies with more megapixels on the sensor. I have a portrait format 40x50 cm print taken from a cropped landscape format image from my 16 megapixel half-frame (APS-C) DSLR, so it's about 7-8 megapixels, and the image is sharp and survives quite close inspection. The important thing is that it was taken with my old-model Sigma 10-20 at F 9.5 which is in the optimum F 8 -F11 'sweet spot' for this lens. The quality of the lens may sometimes be more important than that resolution of the sensor -I know that using only half the frame from an image taken with my Tamron 18-250 at this aperture would not be as good printed this size if looked at too closely.

    A few years ago I had the chance to see a large original Canaletto at an art gallery (over 2 metres wide). At a sensible viewing distance (3 metres perhaps) the buildings looked very detailed, but on very close inspection doorways and windows were often represented by just two brushstrokes - one at the top and one on the left or right depending on the lighting of the scene. Viewing the painting at a sensible distance was obviously the best way to admire it, rather than performing a version of 'pixel peeping'
  5. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    I think it all depends on the intended purpose of the picture. If you're showing a crime scene for legal reasons then detail is everything. If your nickname is "Weegee" then the impact is all that matters! :D
  6. Chester AP

    Chester AP Well-Known Member

    Hence the question I usually ask on the popular 'what camera should I buy?' Forum threads: what do you want to do with your pictures? View them on a PC monitor or small handheld device (so spending thousands of pounds or a camera body and lens(es) is probably pointless when the display device will not show all the benefits), or view as large prints proudly framed on your wall? (where the display 'device' will show the benefits of the investment, if you can afford it).

    I suspect many younger people don't even think about large prints when buying a camera body and lens(es).

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