here is the thing...
some people say save as have a better image quality than save for web
and save for web images are gritty especially viewed in photoshop.
http://img168.imageshack.us/img168/8234/grayvsindex.jpg

then other people say that save as web image has a smaller file size, yet viewed under the image viewer there aren't much differences as long as you use adequate colors.

so what's your choice, better quality or smaller file size? 🤨

Manga-Heaven <3 <3 <3

Save as web, cause the file size is smaller when there isn't 300
shades of gray. Saves time and brain cells.

What do you mean by "gritty?" Maybe you should be viewing those images at 100% or 50% rather than 33.33%. It makes a big difference.

Save as Web not only makes the quality better, it makes the size smaller, imo. Quality for reading. o-o Who wants to open a 70+mb chapter?
Even if Save As makes it slightly better quality, it's barely anything.
Save for Web gives you more options to save, like choosing the number of colors, diffusion, etc.
Imo, it's much better for manga.

♪MONSTARR~ will eat all your cookies and steal your bishies~♪ Φ_Φ

I save as jpgs

[img]https://www.yourgimmick.net/wordpress/wp-content/uploads/2018/09/banner1.jpg[/img]

Your question is all wrong. If I have to try and interpret your intention with it, though, it would be more like:
Which looks better, indexed pngs with very few colours or greyscale ones with 256 colours?

There's no doubt that almost all manga will look better if you save in in 256 colours than if you were to save in, say, 12 colours. But there's nothing whatsoever stopping you from making indexed images with 256 colours, though. Or greyscale images with 3 colours, for that matter.

What matters is not the method you use, it's how many colours you want to allocate (size/quality tradeoff) and what colour reduction algorithm you're using (Adaptive tends to be overall most useful, while Perceptual can be better on greyscale pages made from images that were originally in colour). Personally, I don't go lower than 16 colours, and a few times up to 32 can be useful. Above that, it's really hard to spot a difference just by looking at the image.

Also, what you're seeing in your "comparison" image is just PS being stupid. If you resize an indexed image, it uses nearest neighbour instead of bicubic interpolation. Which is what makes it look extra harsh there. (It's quite possible that some image viewers are equally stupid.)

I ask for which method you prefer to use, not which method looks better. so I meant what I said! >.>

one thing I like to point it out is that...
grayscale mode has 256 colours. to be more specific, black, white and 254 shades of gray in-between. and yes index mode images contain only a pallet of up to 256 colours.

I suppose people who do save for web already know how to do it... like the number of colors you need to use and the colour reduction algorithm you want to choose etc.

nevertheless, I REALLY interested in what you said at last. "Also, what you're seeing in your "comparison" image is just PS being stupid....." that explains why I hardly see differences from two images when it's displayed at 100%. then great differences when it's displayed at 33.33% or something. thx for that. ^__^

EDIT:
I orginally thought that since in index mode, PS selects few colours (up to 256) and replaces the rest of the colours with a similar colour in the pallet unlike grayscale in-betweens are shades, when you zoom out, the naked eye will then notice the differences better o__o

Manga-Heaven <3 <3 <3

o__o
You should always save in grayscale. Never index.
Unless it's a color image.

♪MONSTARR~ will eat all your cookies and steal your bishies~♪ Φ_Φ

The eye can't really distinguish more than approximately 100 light levels, anything more is overkill. Though, if you choose those 100 as wrong as you can out of a total of 256 possible levels, it will be quite visible. What makes sure we can get away with even less in the case of manga is the fact that we can choose what colours to use optimally well (within reason), plus there's noise (i.e. dither) for free already in the images.

And greyscale images do not automatically have 256 colours. Many people seem to think so, but it's not true. The point is that they can have all 256 different levels in the same image, not that they all actually do.

Try leveling a normal 8-bit scan, for instance, then counting how many colours it ended up being. (There are some tricks to get around the fact that you drop resolution in this step, but let's not get into that right now...)

In conclusion, to someone who knows what they're doing, your question makes no sense in its original form. I choose better quality and smaller file size by using the Save for Web thingy correctly.