Using Sigil to get the best I can out of pictures

[rosshalde]

I have a few questions for experienced Sigil Users.

1) If you have a book with many illustrations, what image type do you prefer in order to make the size of the book manageable?

2) How many versions of a book do you make in order to be accessible across differing size screens? Are there some code ideas to minimize the necessary number of versions? Here I don't mean the difference in file type (epub/azw3) but the difference in brand peculiarities/screen size.

3) Can someone share with me the code they use in sigil to make sure that their pics are most adjustable to differing dimensions on e-readers vs all the different tablet shapes/sizes? Right now I have a few options.
a) make everything as if it is for a typical e-reader and keep that image size
b) make 2 versions...1 for typical e-reader the other for larger screened tablets
I am doing this because the larger image is crisper/more pleasant, which looks nice on the tablet, but some e-readers won't auto-resize so the image doesn't fit, therefore the smaller image version.

4) I have tested using the <svg> that Sigil uses to create its covers to help with some of the issues above, but I am looking for advice if this is optimal or if there are better ways to deal with the optimization of images across devices

[rubeus]

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[rosshalde]

So you use the smaller image for everything?
I was considering the opposite, using the larger image for everything and using the <svg> to shrink it down for lower res devices.

[theducks]

Apple will be the death of us all with their ultra hi-res stuff
It is a 'cover,' not a semiconductor mask

Typically, a 2x magnification (400x300 image) looks decent at full screen on ALL my devices .

The rule should be: No single rule

Do you NEED fine, line detail? Hi-Res (800x600, not Ultra-res)
Do minor jaggies hurt anything? Std-res

[rubeus]

.....

[exaltedwombat]

In an eBook, there's a lot to be said for giving any picture that's WORTH seeing the full screen width - maybe even its own page. And when a picture is mere decoration, not really worth seeing, leave it out.

[rosshalde]

Maybe I did something wrong with the <svg>. I copied the code Sigil uses for the cover and used it for other images. When I viewed on the large model Kindle Fire, the Cover was "clickable" in order to enlarge to full screen, but the other pics with the <svg> were not clickable.
Here is the file with a variety of attempts at one image at different sizes and with different codes. Can anyone see why only images 1/4 are clickable and 2/3/5/6 are not clickable (this excludes the cover, which is also clickable.

Some pics are two pages wide. when I insert them into Sigil I usually turn them sideways (long dimension up/down) and make give a height of 700 so it fits on Kobo/Kindle/Nook e-reader. It looks bad on the large 9 inch Fire. I inserted a much larger pic, something like 1400 height and that looks great on the Fire.