14 Replies Latest reply: May 12, 2012 10:29 AM by rshammaa
rshammaa Level 1 Level 1 (0 points)

Hi guys,

 

I have a Panasonic Lumix GH1 with a 14 MP sensor outputting 12-MP RW2 files. I exported them from Aperture 3 Library as original size png's to my desktop. When I clicked on them to check them out, most of them were much larger (up to 21 MP), and some even shrank.

 

Does that mean I can blow these up larger than I could as jpg's?

 

Can anyone figure it out? What happened there? I just changed the file format on them, that's all.

 

Thanks a lot,

 

Raphael


iMac 21.5", Mac OS X (10.7.2), Pages for iPhone/iPad
  • 1. Re: Files exported as png increase in size?
    Terence Devlin Level 10 Level 10 (123,865 points)

    1. MP - mega pixels - has no little bearing on the size of the file. It's a measure of how many pixels are on the camera sensor. Megabytes (MB) are a measure of file size.

     

    2. Original size in Aperture refers to the dimensions of the image - length by breadth, not file size.

     

    3. Changing format will always produce a different file size. Each different format - tiff, png, jpeg etc - all carry their data load in different ways.

     

    4. No you can't blow these up larger than Jpegs. You can't add pixels with Aperture.

     

    Regards

     

     

    TD

  • 2. Re: Files exported as png increase in size?
    léonie Level 9 Level 9 (51,775 points)

    4. No you can't blow these up larger than Jpegs. You can't add pixels with Aperture.

    Are you sure? Never say "no", TD; I am doing just that all the time   Try this:

    • Edit a custom export preset and set the "Size To:" as "Fit within (Pixels).You can specify "Width:" and "Height:" to much larger values then the original image dimensions.

     

    I just enlarged a tiny 677x420 image (87 KB)  to 3000x1861 pixels and 2.9 MB.

    I discovered that when I needed testdata of a certain pixel size.

     

     

    Cheers

    Léonie

  • 3. Re: Files exported as png increase in size?
    léonie Level 9 Level 9 (51,775 points)

    Larger.png

  • 4. Re: Files exported as png increase in size?
    léonie Level 9 Level 9 (51,775 points)

    croc.png

  • 5. Re: Files exported as png increase in size?
    Terence Devlin Level 10 Level 10 (123,865 points)

    Dead right.. but how was the quality?

     

    Regards

     

     

    TD

  • 6. Re: Files exported as png increase in size?
    léonie Level 9 Level 9 (51,775 points)

    Dead right.. but how was the quality?

    You don't really have to ask, do you?

    Blurry - as horrible as is to be expected when you simply enlarge the number of pixels by a factor of 12, without adding any new information - a waste of storage and not to be recommended. As I said, I simply needed a large image file with a fixed numbers of pixels for testing.

     

    Regards

    Léonie

    Australien-Krokodilblownup.jpg

  • 7. Re: Files exported as png increase in size?
    rshammaa Level 1 Level 1 (0 points)

    Thank you TD.

     

    The MB informs us of file size-  "digital" file size, and the MP informs us as to how that amount of info is being distributed 2-dimentionally. Correct?

     

    So when I worry about how big a blow up a file can provide in inches - and still maintain exhibit quality, which is what I need, I need to look at MB, not MP; and factor in whether it is being printed at 200 or 300 DPI. Right? But how?

     

    The literature on line is all over the place on this and use MP not MB to go by. My images tend to be  little over or a little under 12MB - with exceptions when the cropping is more severe of course. So, how large of a high quality print can I hope for at 12MB per image?

     

    I am at a crosroads and need to decide whether I can keep and expand on my GH1 equipment or loook for full sensor sized 35mm cameras, albeit with the appended consequences in camera and lens size, combined additional weight, much larger file sizes, much larger backup drive sizes, and on and on.

     

    Any input will be gratefully accepted. Thanks.

  • 8. Re: Files exported as png increase in size?
    rshammaa Level 1 Level 1 (0 points)

    Thank you Leonie!

  • 9. Re: Files exported as png increase in size?
    léonie Level 9 Level 9 (51,775 points)

    The MB informs us of file size-  "digital" file size, and the MP informs us as to how that amount of info is being distributed 2-dimentionally. Correct?

    You got it - nearly.

     

    The MB informs us of file size-  "digital" file size

     

    What exactly can be inferred from the filesize? The filesize will depend on the resolution (pixelsize) and on the compression scheme.

    • Any lossless format (tiff, png, raw, psd) will result in large filesizes, in especially when set to 16 bit.
    • Lossy compression (jpeg) only approximates the image and will degrade the image, but will reduce the file size depending on the setting of the quality slider.

     

    So, how large of a high quality print can I hope for at 12MB per image?

    That is easier to answer for 10 MP - a simple piece of arithmetic:

     

    For example, my Lumix FZ28 raws have a dimension of 3652 × 2738 (10.0 MP)

     

    If I print it at 300 dpi (dots per inch) the width will be: 3652 points / 300 dpi

         = 12.2 inches x 9.12 inches

     

    If I print it at 200 dpi (dots per inch) the width will be: 3652 points / 300 dpi

         = 18.26 inches x 13.69 inches

     

    If the compression is lossless (tiff, png, raw) printing at this size will give a very good quality, but if you have a jpeg format with low quality stting, the print might show artefacts and be blurry.

     

    Regards

    Léonie

  • 10. Re: Files exported as png increase in size?
    rshammaa Level 1 Level 1 (0 points)

    Thank you Leonie.

     

    You divide the original pixel dimensions by either 200 or 300 DPI to get the maximum print dimensions - and of course, images can be printed smaller without concern.

     

    I looked at the dimensions of one of my images which is 11.4MP and, at 300 DPI, yields a 9"x14" print by similar calculations; and a 14"x20" print at 200 DPI. To me, both prints would qualify as respectable in terms of their physical dimensions. I think I get it now.

     

    And I also understand that 300 DPI is not necessarily better, or sufficiently better, than 200 DPI in terms of limiting desired print size. Testing a particular image at either setting is the answer.

     

    I am now reconciled with the notion of sticking with my GH1 (and maybe waiting till the upcoming photo show in October and looking at the GH2 or GH3?)

     

    Thanks a lot.

  • 11. Re: Files exported as png increase in size?
    léonie Level 9 Level 9 (51,775 points)

    You are welcome!

     

    Léonie

  • 12. Re: Files exported as png increase in size?
    rshammaa Level 1 Level 1 (0 points)

    One more question if I may.

     

    Does one get a better print from a larger file of the same exact subject? Is it useful to switch to a camera with a larger sensor even though the final print is of a predetermind and technically appropriate size regardless?

  • 13. Re: Files exported as png increase in size?
    léonie Level 9 Level 9 (51,775 points)

    Larger sensor and larger file size are not necessarily the same - so I am not quite sure what you are asking.

     

    The image quality is determined by the spatial resolution and the photometric resolution (I'll ignore the quality of the lens for now and talk only about the sensor).

     

    • The spatial resolution depends on the number of pixels the sensor will sample from the image.
    • The photometric resolution will depend on the signal to noise ratio, and that will depend on the size of each cell in the sensor. A large sensor will have a better signal to noise ratio than a smaller sensor of the same pixel size. If you compare sensors don't look at the pixel size but at the dimensions of the sensor.

     

    The signal to noise ratio is important, if you need a long exposure because of insufficient light, e.g. time at dawn or dusk.

     

    Does one get a better print from a larger file of the same exact subject?

     

    To produce the print at the correct size the image will have to be subsampled. If you print from Aperture then Aperture will do that perfectly. I do not know what kind of subsampling the print service will use that you send your images to. But it should suffice to send a high quality image with exact the pixelsize you need.

     

    Regards

    Léonie

  • 14. Re: Files exported as png increase in size?
    rshammaa Level 1 Level 1 (0 points)

    Thank you Leonie.