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Thread: Picture sizes

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    3 Star Lounger
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    Picture sizes

    My new Panasonic camera came with software "SD Viewer" that defines picture sizes in pixels viz: 2560x1920 or 640x480 etc. etc. Is there somwhere a quick and easy conversion chart that shows comparative sizes in inches?

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    Plutonium Lounger
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    Re: Picture sizes

    I'm not near the pro at photography that some of our fellow Loungers are, but I have my camera's default set to 1600 x 1200 and if you check the second of Tony's links you'll see that that's a tad larger than an 8.5" x 11" sheet of paper. I don't mind resizing downward just enough to fit a picture on glossy paper, which I really don't do that much anyway. And, at 1600 x 1200 I can cram quite a bunch of pictures on my 256 meg memory stick. My compromise...

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    Super Moderator jscher2000's Avatar
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    Re: Picture sizes

    Ah, you have a 5 megapixel camera. Well, there actually are no comparative size in inches. Instead, there's an optimal pixels-per-inch ratio for each different output device. For example:

    Internet Explorer screen display: shows 96 pixels per inch
    Typical Canon dot matrix printer: prints at multiples of 180 pixels per inch
    One-hour printer at our local Costco: prints at 320 pixels per inch

    For immediate viewing, you can downsize your image files to something like monitor resolution (e.g., 800x600, 1024x768). For 4x6 prints, a "2 megapixel" resolution of 1600x1200 usually is fine. But if you want to crop your image to focus on particular details (or remove stuff from the sides), you want to have enough pixels left over to match your target output device. For this reason, and to be able to output with the best quality for those rare masterpieces, it is a good idea to keep an "original" of your photos somewhere (hard drive, CD or DVD). In other words, when downsizing, don't overwrite the originals.

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    Re: Picture sizes

    Just to add to what Jeff said, something else to keep in mind is that you should save the original image in a lossless format, such as Photoshop (.PSD), Paint Shop Pro ( .PSP), or .TIF, and NOT in .JPG format. Of these, .TIF files do NOT support layers, so are less useful when editing. There are other, less common lossless formats such as those used by other photo editing programs (Photo Impact springs to mind) that are also good, but they aren't used by many people, so sharing files in these formats is difficult.

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    Super Moderator jscher2000's Avatar
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    Re: Picture sizes

    I have used PSD format when I want to save my layers in PS Elements, but the files are so ridiculously huge that I can't recommend doing it for all images. Basically, if you spent 5 minutes doing quick adjustments that you easily could do again, it doesn't seem worth using the PSD format. Instead, a "maximum quality" JPEG seems perfectly adequate. Yes, some color information is discarded, but at that level of compression it should not be noticeable to humans. <img src=/S/grin.gif border=0 alt=grin width=15 height=15>

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    Re: Picture sizes

    I agree that Photoshop's files can become quite large, and that saving all original files in .psd format (or in another layered format, such as Paint Shop Pro's) is not necessary, and can rapidly fill one's hard drive. What I was suggesting is that for photos that will need later editing, more complex adjustments and/or work, Photoshop's format is ideal, since it allows for working with layers. Layers are necessary for using blending modes, alpha channels, and so on, as well as most complex actions (graphic macros that work in Photoshop). If, on the other hand, you merely want to do simple cropping, sampling down, etc., and multiple layered compositing isn't necessary, AND you don't plan on further editing, a file saved as a .jpg may be just the ticket.

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    Re: Picture sizes

    Thanx Tony, but clicking on either link fails to connect. Do you have a website for that info??

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    Re: Picture sizes

    Both links are to websites, I just checked them and both sites are working.

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    Re: Picture sizes

    What I find intriguing is that Photo Editor (for example) will give you a size of a jpg which seems unrelated to the number of pixels. Is this info stored with the picture itself, or is it something to do with the compression / 'quality factor' it is saved with?

    Otherwise, would I be right in supposing that the best print quality would be obtained by matching the width to the picture-pixel : printer-resolution ratio? In other words, a pic 2096 pixels wide photo printed on a 600DPI printer would look best at 2096/600" (3.49333") wide - or multiple thereof?

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    Super Moderator jscher2000's Avatar
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    Re: Picture sizes

    Most dialogs seem to want to comfort you with short-hand descriptions of how all these numbers relate to one another, rather than admitting that it's all very messy.

    In your example of a 600 dpi printer, it depends on what the dpi means. In the case of inkjet printers, I have read that it refers to dots of different colors, so a printer that is printing at 720 dpi might really have a native resolution of 180 ppi (pixels per inch). But I haven't tested it.

    Generally speaking, if there is any mismatch at all between the pixels and the number of dots needed to fill the desired space, some software, either an application or a print driver, will resize the image, either by collapsing pixels or interpolating new ones. Some software has a reputation for doing an especially good job at this, I've seen recommendations for Qprint but haven't tried it. Given a choice, though, you probably would get the best results by creating the appropriate size in advance. There are vigorous debates over which software does the best job at "upsizing" images; I think one called Genuine Fractals is supposed to be really good, but I've also seen praise for Irfanview's "Lanczos" (apologies for misspellings, as that is from memory) method is good. And of course if Photoshop is the tool at hand, "bicubic smoother" is recommended for upsizing and "bicubic sharper" for downsizing. Except for screen shots. <img src=/S/laugh.gif border=0 alt=laugh width=15 height=15>

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    3 Star Lounger
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    Re: Picture sizes

    Thanx to all who posted. The Panasonic tech rep finally phoned and we kicked it around a bit and he said he doesn't use the bundled software "SD Viewer" himself. He uses Photoshop for all phases of editing. I have the CS version and will probably do most of work with that. Just a plug here for Panasonic tho for anyone considering a new camera their DMC-FZ5 is a real beauty.

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