Question: more pixels at reduced size, is there a difference?

Started 6 months ago | Discussions thread
rhlpetrus
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Re: Question: more pixels at reduced size, is there a difference?
In reply to Mark Scott Abeln, 5 months ago

Mark Scott Abeln wrote:

rhlpetrus wrote:

Supposing one uses as final output files at 16MP, at base ISO (100), would one have any technical difference between images from Nikon Df, D610 and D810 (no AA)?

More probably depends on the lens, but various cameras do have differing strengths and weaknesses. Megapixels are hardly the only factors worth considering. Ergonomics, cost, and color rendering are very important also, among other things — and color quality is sometimes lacking compared to older cameras, especially with Nikons.

Even when viewing images on the web, at greatly reduced resolution, medium-format images can often stand out, especially if they were well-made with good optics. The difference is a matter of degree, however, and many folks are hard-pressed to distinguish good photos taken with an APS-C sensor compared to a FF one. There are technical differences in image quality and they might make a difference in extreme cases, but not necessarily in most common instances.

How much does the downresing technology impact results? If any, which downresing technology is best?

This is a very important step, and this is where better cameras can benefit or be harmed by what technology you are using.

For example, suppose you are downsizing an image strongly, going from 5000 pixels across to 500 pixels. Let’s consider two simple and extreme cases of downsampling an image:

  • Averaging — every block of 10x10 pixels is averaged down to one pixel.
  • Decimation — only one out of every 10 pixels is kept, and the 9 others discarded.

Decimation would produce a very sharp image but will have lots of digital artifacts. Averaging will produce a softer image. Some sort of compromise between the two is instead needed — bringing out some the sharpness while not having too many artifacts.

These articles from the ImageMagick software package might be interesting:

http://www.imagemagick.org/Usage/resize/

http://www.imagemagick.org/Usage/filter/nicolas/

Is there any advantage in using a camera for which 16MP is the resident pixel count?

There are practical advantages. I use a 16 MP camera, and processing images on my 2011-era computer is slow and harms my productivity since I inevitably go off and do something else rather than wait for a process to complete. I’d really suffer from long waits if I had to process 36 MP images. I’ve recently purchased a newer computer because of this (but haven’t got it fully set up yet).

16 MP cameras have antialias filters, and these do have a purpose, which is well-conditioning the analog signal before it gets converted to digital. But as megapixels goes up, this becomes less useful as the lens itself usually provides the needed blur.

If there are differences, which aspect would have any real photographic impact? DR in favor or D610 and D810? Possibly color separation? Any difference in actual resolution between final images?

Thanks

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Renato.
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Thanks, very good comments, just a math item: if you take a 5000 pix and average blocks of 10x10 pixels to 1 pix you get a 50pixel final file. But I got the idea. Even though usually IQ is foremost for me, I also have to consider the way different cameras handle. The D810 is a relatively bulky camera for most uses, while a Df would be much lighter and smaller. Maybe the solution is to get both ;-).

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Renato.
http://www.flickr.com/photos/rhlpedrosa/
OnExposure member
http://www.onexposure.net/
Good shooting and good luck
(after Ed Murrow)

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