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Thread: image size

  1. #16
    PRC Member spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all
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    Quote Originally Posted by zomod View Post
    Did you see typesetter message, to which I replied ?
    " I do not recommend to use Photoshop for upscaling because of nasty artefacts bicubic interpolation does."
    yes, of course. he is talking about artefacts caused by pixel interpolation for upscaling picture resolution and gives some hints how to avoid them.

    you are talking about image compression artefacts which dont belong here at all since this is a complete different issue! other file formats dont help here either.

    do you spot the difference??? i dont think so!
    Last edited by spider; 04-07-2013 at 06:07 AM.

  2. #17
    Junior Member elmut is on a distinguished road
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    Quote Originally Posted by spider View Post
    you have to take in account the method of printing: offset printing with 175lpi?
    or digital printing with e.g. 1440 dpi printing resolution?

    using some math from elementary school you will find out that your image only gives an output resolution of 85 dpi! (6675 pixels / 200 cm * 2.54 = 85 dpi)

    imho this is not enough, even for digital printing. you should double the resolution with photoshop to get 170 dpi. this might be sufficient for digital printing but depends of course on the details in the image and the distance for viewing the print result.

    if you are going to offset printing with 175 lpi you have to scale the image in photoshop by factor 4 giving you 340 dpi for output. this will result in a very big file size of course.
    hello everybody, first of all i would like to thank you all for answering my question. Yes im a lil bit confuse reading some other doubts. I'm agree with you, i've already heard about this image formula.
    By the way it will be a hardback poster 140x200 cm that will be use as expnts during the event, so the distance for viewing maybe actually change. So going to the point, i would like to know how can i scale my photo to be able to have this 340 dpi for output.

    thank you

  3. #18
    Junior Member elmut is on a distinguished road
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    Quote Originally Posted by typesetter View Post
    In fact, required resolution is determined by the image itself.
    If the image has much high-contrast detail - then it does need a higher resolution. If the image is blurry, does not contain fine details - then resolution can be significantly smaller.

    As for this particular case - depending on printing technology (i.e. offset or inkjet) your printer will inform you about optimal incoming image resolution. And if your image doesn't meet the requirement - you can "blow up" its resolution with specific plugins (Fractals Print Pro, AlienSkin Blow up, Pxl SmartScale etc). I do not recommend to use Photoshop for upscaling because of nasty artefacts bicubic interpolation does.
    hello spider, thanks for the reply, i wuold like to ask how does this puglins work? where can i get them are they free or with fee? if this this the best solution could i ask you if could you please give me some tutorials or guide on how to scale the image to have the optimal incoming image resolution?

    thank you very much

  4. #19
    PRC Member spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all
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    Quote Originally Posted by elmut View Post
    hello spider, thanks for the reply, i wuold like to ask how does this puglins work? where can i get them are they free or with fee? if this this the best solution could i ask you if could you please give me some tutorials or guide on how to scale the image to have the optimal incoming image resolution?

    thank you very much
    hi elmut!

    the answer from your quote is not mine.

    there are several applications for image scaling, either as ps-plug in or standal.o.n.e
    they are not for free and you have to see if they are available for mac or pc.
    they take several approaches and different algorithms for interpolation / resampling.
    which algorithm is the best for upscaling depends heavily on the type/contents of the image.
    so you have to test different products with different settings to find the best result on your own. fiddling with the settings is not easy and takes a lot of image calculation time for such a big image.

    i recommend to try photoshop scaling first. if you need a scaling of 400% make 2 sequential steps with 200% and verify or adjudt the sharpness after the first and second step. maybe this result is fine for your purpose.

    you didnt tell us yet which is your printing method.

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  6. #20
    Junior Member zomod is on a distinguished road zomod's Avatar
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    Rephrase the question of spider, it will be a single poster, there will be enough? Elmut if you give a link to this image here, I can see and show you the possible outcome of an increase in the interpolation, it is not difficult.

  7. #21
    Junior Member elmut is on a distinguished road
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    Quote Originally Posted by spider View Post
    hi elmut!

    the answer from your quote is not mine.

    there are several applications for image scaling, either as ps-plug in or standal.o.n.e
    they are not for free and you have to see if they are available for mac or pc.
    they take several approaches and different algorithms for interpolation / resampling.
    which algorithm is the best for upscaling depends heavily on the type/contents of the image.
    so you have to test different products with different settings to find the best result on your own. fiddling with the settings is not easy and takes a lot of image calculation time for such a big image.

    i recommend to try photoshop scaling first. if you need a scaling of 400% make 2 sequential steps with 200% and verify or adjudt the sharpness after the first and second step. maybe this result is fine for your purpose.

    you didnt tell us yet which is your printing method.
    ok i understand, it seems like it's not that easy as i thought it would be
    anyway for the printing method i'm not quite sure but i think we will be working on offset printing with 175 dpi as you sad and obviously you've already gave me the resolution for digital so i think i will be focusing on offset .

    im sorry spider if i ask too much, but could you please give some guide on how to scale the image as youtold me?

  8. #22
    PRC Member spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all
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    Quote Originally Posted by elmut View Post
    ok i understand, it seems like it's not that easy as i thought it would be
    anyway for the printing method i'm not quite sure but i think we will be working on offset printing with 175 dpi as you sad and obviously you've already gave me the resolution for digital so i think i will be focusing on offset .

    im sorry spider if i ask too much, but could you please give some guide on how to scale the image as youtold me?
    hi!

    offset printing uses 175 lpi (lines per inch, dont mix up with dpi!) as standard screening frequency if we are talking about coated paper stock.

    the ideal output resolution for images in this case is 350 dpi (double value of 175 lpi).
    when we are talking about your image from the first post you have a resolution of nearly 85 dpi now.

    as i wrote in my previous post you should go into photoshop and scale the image by 200%. this will give you a resolution of 170 dpi. next step is to control the sharpness of the result visually. you can sharpen the image slightly with the unsharp mask command if necessary. now scale the image a second time by 200%. this will give a resolution of 340 dpi which is near to our ideal goal of 350 dpi. maybe you have to use the unsharp mask once again.

    thats it!

    it is essential to use exact scaling factor of 200% so the pixels just have to be doubled for interpolation. this is no real interpolation since photoshop has no "half" pixels to calculate.

    but remember: this is the theory for optimum offset printing results. if your image has not so much detail an effective output resolution of 250 - 300 dpi might be enough.

  9. #23
    Banned maeiwill is on a distinguished road
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    its too better to know the paper gramage

  10. #24
    PRC Member spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all spider is a name known to all
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    Quote Originally Posted by maeiwill View Post
    its too better to know the paper gramage
    for sure! and you have to keep in mind the phase of the moon and the hair color of the photographer! OMG!!!

  11. #25
    Junior Member francuzzoterz is on a distinguished road
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    I think maeiwill suggesti is fine-

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  13. #26
    Banned Kalle is on a distinguished road
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    I can definitely recommend Alienskin blow-up. I've used it to enlarge successfully way smaller pictures to print them on a digital printer to posters of 1300 x 2200 mm. I did a whole showroom full of posters for a client and the results are awesome, even from pictures as small as 1600 x 1000!

    Do's:
    - use Alienskin Blowup to enlarge in step to the required size and resolution.

    Don't s
    don't save as jpeg, save either as psd or tiff or other uncompressed file format
    don't us Photoshops upscaler, the results are terrible

    I can help with a Mac version of blowup. PM me. Or use a trial version if its a once off.

  14. #27
    eqL
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    try 600dpi!

  15. #28
    Junior Member kookos is on a distinguished road
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    I would use 300dpi or 150dpi depending on printer. 600dpi is too much.

    At our school they recommend 150dpi for printing with roll printer. That's because the printer is old and 150dpi is maximum and using 300dpi makes printing just slow. The quality isn't any better.

  16. #29
    Junior Member chuckdee is on a distinguished road
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    Quote Originally Posted by elmut View Post
    hello everybody i would like to ask some question on what would be the best image resolution for printing a poster that is 140x200 centimeters. I have already a picture that has 5000x6675 pixel and 600 DPI do you think its already enough or do i have to resize the picture?

    Yes, that's more than adequate.

  17. #30
    Junior Member pupo is on a distinguished road
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    if image's sharpness is good, should be ok.
    but it's depending of the use of poster: for fans room is ok, for a museum probably not
    (sorry for my poor english)

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