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Thread: Digital photography

  1. #1

    Digital photography

    How many megapixels would you need to blow up a picture to 16x20 without loosing quality of the picture?

    I have a 7.1 megapixel camera and blew up a pictures to 16x20 and it was a little distorted.

  2. #2
    Doug Dolde
    Guest

    Digital photography

    Read this thread for some possible clues

    http://largeformatphotography.info/lfforum/topic/504529.html

  3. #3

    Join Date
    Apr 2004
    Posts
    832

    Digital photography

    It appears that the OP, John Werczynsi, thinks that Large Format begins at the print stage and magically works backwards. Hey, get a clue; large prints begin with the original medium. Now what are you doing here, Mr. Werczynski?

  4. #4

    Join Date
    Nov 2003
    Posts
    1,218

    Digital photography

    I agree with jj. He should go to the photo net digital processing forum.

  5. #5

    Join Date
    Jun 2004
    Posts
    1,182

    Digital photography

    Gee,

    With the exception of one, with garbage replies like that, I can see why new people are turned off by the large format community.

    John let me apologize for the junk above and try to answer your question. If you're shooting with a 7.1MP camera, I know you are using a higher end point and shoot. The sensors in these are small compared to standard DX sensor DSLRs from the likes of Canon, Fuji, Nikon, etc. While the sensor may have more pixels, because it is smaller than the normal DX or full frame sizes, you're getting far more noise in a print the size of 16x20. This is but one issue. Others include the quality of the lens the camera uses, iso used, etc.

    In short, an 8MP sensor properly processed in a good converter (like Capture one or Rawshooter) can deliver a decent 16x24. But I would say that it requires a decent DSLR like the D2X from Nikon, the 5D or 1Ds MK2 from Canon to give a truly detailed, sharp, low noise print.

    Best regards,

  6. #6

    Join Date
    Dec 2005
    Location
    Southern California
    Posts
    2,721

    Digital photography

    What Dave said.

    Also, the upsizing method and it's place in the post-processing flow can influence the final quality as well. Not much, but every little bit counts at that level.

    To the point: If you know you are going to upsize (upres) the image, this should be the first step in the flow. It should also be done incrementally, instead of in one big pass. Keep increasing the size by no more than 10% in each step until you get to the desired size. Then apply all the other steps and THEN apply sharpening (USM) as the very last step.

    As a final note, you will also achieve much better quality if you shoot raw and do all your processing until the sharpening step on the 16-bit file (per channel) instead of an 8-bit.

    And don't mind some of the grouches you will inevitably encounter here - we're mostly a bunch of grumpy, aging men (save for a few ladies) here and that kind of attitude is part of the local folklore. There are some good souls under the crust though, you just need to be patient.

    Regards,

  7. #7

    Join Date
    Jun 2004
    Posts
    1,182

    Digital photography

    Hey Marko,

    If you're using an older version of Photoshop, then stairstepping is good. If you have the newer versions, I suggest the following routine:

    - Presharpen the converted image ( Try USM 300, .3, 2 ), fade luminosity

    - Interpolate using bicubic SMOOTHER, in one step.....but interpolate 20% larger than your desired print size (ie; if you want 16x24, interpolate to 28.8")

    - USM to taste ( Try 50, 1.5, 2 to start), fade luminosity

    - Downsample back to 16x24 using bicubic SHARPER

    I have found that when converting my RAW files in Capture One, and using this interpolation routine (which by the way is also mentioned here:

    http://www.outbackphoto.com/workflow/wf_60/essay.html

    ....I get finer detail, much less haloing, better accutance.....but at the expense of a slight bit more noise. This noise though is typically visible only on screen at 100%, but not so much on print, and is far less than anything you would get with film.

    This is a simpler version of the routine I use, which involves interpolating and sharpening LAB mode channels differently, and seperately.....but it still does a fine job. Play with the presharpening and post sharpening a bit as every camera as well as every image requires differing amounts.

    Best regards,

  8. #8
    Multi-format, with beard.
    Join Date
    Mar 2005
    Location
    Pasadena, CA
    Posts
    390

    Digital photography

    While I too think you might find better information elsewhere in the digital and publishing
    boards, you can simply try it out to see what happens. For the price a large format photographer
    may pay for a sheet of film and custom processing, you could simply upload a file to
    a pro lab and then see it in all its glory, then be the judge. You do deserve better than
    a crusty answer though, as you may end up turning to ( or returning to! ) LF photography
    after exploring the modern day legends and mystique of the megapixel!

    IF you are willing to accept 300 pixels per inch as the original standard for quality,
    and if your image needs no cropping, and if all the pixels in your megapixels are
    "effective" you would need 4,800 by 6000 pixels in the most simple sense, or 28,800,000
    pixels. If you use 1,000,000 for mega, then you would need 28.8 megapixels. If you
    use 1,048,576 for mega, then you might say that you need 27.5 megapixels. Generally,
    a 16x20 will look very nice at 240 pixels per inch output resolution, at normal distances,
    or 18,432,000 working pixels. I seem to remember Canon bragging about finally being able to
    make a decent 11x17 ( full page ) print with their flagship DSLR somewhere, so that might
    be an indication of what one camera maker deems "without loss of quality".

    Naturally, most digital cameras will not do 16x20 without cropping, and most digital cameras have pixels that are not "effective", so in reality, you might need a 22 megapixel camera to make
    a very high quality "honest" 16x20.

    "Loss of quality" may come from other factors such as the optics used to make the
    image in the first place. Most small digitial cameras ( except for MF ones that happen to
    be fairly small now, such as the H1 ), suffer from inferior optics. No amount of megapixels
    will make up for mirror vibration, camera shake or inferior optics.

    Quality, beauty and satisfaction are in the eye of the beholder or creator.

  9. #9

    Digital photography

    Dave, would you please devote a paragraph or two describing your upsizing techniques? Also, is it your invention, or is based on something I can read on the web?

  10. #10

    Join Date
    Apr 2004
    Posts
    832

    Digital photography

    Quality, beauty and satisfaction are in the eye of the beholder or creator.

    But in this forum it all starts from LF film. Why are you all entertaining a poor soul who wandered in here with a purely digital issue? Look, he ain't starving or homeless! Send him away.
    Gently, if you like.

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