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Needing a picture enlarged

Discussion in 'Help Team' started by mygirljess2775, Feb 17, 2017.

  1. cliveva

    cliveva Well-Known Member

    What I was trying to say, was that when you magnify an image, from small sensor v a large one, pixilation occurs much sooner with the small one.
    When I view images from a 10mp Leica compact, it occurs at about 200% magnification, were as on a full frame 36mp, it occurs at around 400%.
    So there is a maximum one may enlarge, for each sensor size.
    Look at the image on a computer, magnify until you can see pixels, reduce until they disappear, multiply the sensor area by that amount, and that should be the maximum, quality print size.
     
  2. PeteRob

    PeteRob Well-Known Member

    If you are going to see single pixels as solid squares on a monitor then you need 4:1 (one pixel becomes 2x2) or 9:1 (one pixel becomes 3x3) etc. else the computer has to randomly orientate the extra pixel(s). On my monitor I have to go to 16:1 (4x4) to say I can really see squares, which is probably a reflection on my eyesight. Otherwise above 1:1 it just looks a mess as the "extra" pixels are inserted.

    I don"t see what the pixel count has to do with the appearance of solid blocks at high magnification on a screen. For printing it is the pixel information per inch on the paper that counts. As far as I can see your formula ends up with a very small sensor sized image.
     
  3. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    Of course it does! It just has nothing to do with the sensor size. Look at what you wrote - a 36MP sensor has 3.6x the pixels of a 10MP sensor so of course pixelation will occur more quickly with the Leica images. It would happen in exactly the same way if the small sensor Leica had 36MP and the big sensor full frame had 10MP, except it would be the full frame that would pixelate first. Just to clear something up - are you confusing pixel count with sensor size?
     
  4. EightBitTony

    EightBitTony Well-Known Member

    That is a very confused message.

    An image has a number of pixels. A print has a number of dots per inch. This has nothing to do with physical sensor size and everything to do with the number of pixels in the image that's being worked on. None of this helps the original poster. We need to know what image they were working with or we can't help.
     
    RogerMac likes this.
  5. AlexMonro

    AlexMonro Old Grand Part Deux

    When you are talking about "small sensor" and "large one", are you using small and large in terms of pixel count or physical dimensions?

    The examples you give have significant variation in both quantities.
     
  6. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    I asked that above but we don't seem to be getting an answer. :(
     
  7. cliveva

    cliveva Well-Known Member

    physically larger. It was merely an observation. I was trying to put in words why a 8mp sensor image could not be enlarged beyond a certain point.
    Yes the math is wobbly, was hoping to be corrected.:)
     
  8. RogerMac

    RogerMac Well-Known Member

    "Exceptional quality" "Phone camera image" and "24x36 prints" are are probably another example of being able to get any two but not all three
     
    Gezza likes this.
  9. AlexMonro

    AlexMonro Old Grand Part Deux

    But pixellation is nothing at all to do with the physical dimensions of the sensor. It depends on the pixel density (pixels per inch) of the print, and the viewing distance. A common rule of thumb is that you need at least 300 PPI for prints vied from close up, e.g. postcard prints viewed in the hand, and prints viewed from further away can get by with a lot less, maybe 150-200 for posters on a wall, down to a handful for large advertising hoardings.

    The OP's S3 camera has 3264 pixels across, so with no additional cropping other than to correct the aspect ratio that with give about 90 PPI on a 36" wide print, so pixellation may well have a visible effect at likely viewing distances/ However, I've made a 20x30" print from an image taken with a 9Mpxl bridge camera, which worked out at about 115 PPI, and that doesn't look at all bad unless you press your nose against it!

    Perhaps if the OP comes back with more information, we could offer some more helpful suggestions, e.g. up-rezzing if it's just the printers demanding 300PPI+ (not that I recall having any problem getting Photobox to do the 115PPI print mentioned above).
     
    cliveva likes this.
  10. RogerMac

    RogerMac Well-Known Member

    I keep a 6x4 print beside my printer that is a tiny crop from a 4/3 jpg and it comes out at 180 pixels per inch, it appears sharp even if I use a magnifying glass to view it closely The next stage up (roughly equivalent to 115 ppi) still looks sharp at reasonable viewing distances but 90ppi is unusable. All this is on a good inkjet and I believe commercial printers are a lot less forgiving

    The OP did initially ask for "excellent" quality and 24x36 (That's larger than A1) and
    in the absence of further information perhaps we should not waste any more time
     
  11. PeteRob

    PeteRob Well-Known Member

    I just tried printing a heavy crop at A3. It worked out at 113 ppi. I asked LR to upsize to 300 ppi and set print sharpening to high and the result is better than I expected it would be.
     
    cliveva and RogerMac like this.
  12. RogerMac

    RogerMac Well-Known Member

    It looks as if we are homing in on a consensus that 150 is usable and with care a bit lower. However that's probably with good lenses and image stabalisation I really think that to get that from a camera phone would require a magic wand and also the kind of tobacco that Mr Trump uses to report the security situation in Sweden
     
    Last edited: Feb 20, 2017
    cliveva likes this.
  13. cliveva

    cliveva Well-Known Member

    P.S.- actually cant see pixels from 36mp, even at 800%, was using it as an analogy.
    Useful stuff about PPI, thanks all, not even my enquiry. :oops:
     
  14. Craig20264

    Craig20264 Well-Known Member

    I guess she wasn't really that bothered anyway. :confused:
     
  15. EightBitTony

    EightBitTony Well-Known Member

    Or got put off by the side conversation. Or asked the question in 10 places and got an answer in one of them. Or was unhappy no one just said 'yes, here's how ...'.
     
  16. PeteRob

    PeteRob Well-Known Member

    I thought that is what I did :)
     
  17. RogerMac

    RogerMac Well-Known Member

    Or was really annoyed that we asked detailed question that she probably thought were none of our business. Incidentally if the OP did find a way to do what she wanted it would be interesting to know
     
  18. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    Besides which, side conversations are what makes a forum great! ;)
     

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