Quote:
Originally Posted by Ripplinger
I'm sure DaleDe was using "pixels" in reference to the width and height of the finished image, which is more important for spacing in epubs than dpi.
Such as a small logo often found in the published dates page can be as small as 40x40 pixels. I recently scanned an old book with 2 signatures included, one just an initial, and one the entire name, and they were 54x40 pixels and 253x40 pixels. A larger logo for the book was 150x110.
There's a never a set size you can predetermine while scanning to know what size will look best once you get the words around it in the ebook. Which is why I always scan in the highest res or dpi possible. That way I have a good clean image to play around with while I determine the proper size for the image and I never have to go back and rescan it again. And the only way to determine that is to try a size, put it in the ebook, load it in your reader and check it. What might look great on your PC in Calibre's viewer might look way too big on your reader. There's a lot of resizing usually to get it right.
It's all about the spacing, which is the number of pixels for width and height, once it gets into the ebook itself. Dpi doesn't matter at all in the end result.
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Well, in this context, dpi doesn't matter at all. DPI only relates to printers, AFAIK, and of course, scanners (about which I, at least, wasn't really talking). I was very specifically talking about PPI, or pixels. To me, a saved image contains the pixels it contains--if it has, for example (just to make my life easy), 96x96px, on the iPad 1, it will display 1" x 1". On an older monitor, with a "rez" of 72dpi, you should, in theory, get a slightly larger image
display. To match a specific device, you match the pixels of the screen resolution, whether that's 1024 by whatever, etc.
With regard to eBooks, I'm reasonably comfortable that somewhere between 72 and 96ppi tends to get you a credibly good image for most purposes.
@derangedhermit: Honestly, I disagree about the "optimum" process, and I think downsizing images so that
no e-reader resizes it does not work. In an instance as narrow as the one you've cited, sure--that will work; but generally, it won't. If you're using an ePUB reader, it will resize it, and even older Kindles will resize images (in an attempt to fill the screen) unless you expressly set the height and width of the image in hard pixels. Hell, it will get resized if you're using an i-anything and rotate the device. What you're suggesting only works if you're making books for yourself, or have finite control over what devices a book will be read upon. Given that those of us making them commercially have zero control, the safer assumption is that people will see them on larger devices, so that when the image is reiszed, it's resized into a smaller space, not enlarged into a space it doesn't really have the size or rez to fill well.
While some images definitely benefit from additional rez and format (e.g, pngs), many don't, and people waste size on over-rezzing images, particularly if they're driving for i-devices.
This whole discussion reminds me of High School (back when Dinos walked the earth). In geometry, my long-suffering teacher endeavored to get me to agree that a bunch of points--which didn't exist--constituted a line. Now, of course, I knew damn well what she meant, but...now we're having a conversation about what resolution is the best, when a pixel doesn't even have an actual dimension. Talk about baking your noodle. And, probably, grossly over-thinking something that, for the most part, doesn't need over-thinking. The average ebook cover of 600x800 will work just fine. Whether at 72 or 96. ;-)
@Jimtheobscure:
Make sure that when you are calculating the final size of the html file, you add the image folder size to the html file size. However, unless your images have tiny writing, or are line drawings, charts, etc., it's extremely unlikely that you need 300ppi images
inside the eBook. It's not a bad idea to start out with that much rez--it gives you more pixels to work with (less space between pixels, in other words), but--and watch out now, this will be heresy if real image guys are reading this--you can probably safely
batch convert those down to 96 and be fine. Save a ton of room in your ebook. (I'll get flogged for suggesting batch-conversion, but again: it depends on the images, and your experience. My Prod. Mgr., who is a photographer, faints when he hears me utter
The Batch-Convert Words of Doom.
)
Hitch