Re: Mega Pixel Myth

On May 23, 10:38 pm, acl <achilleaslazari...@xxxxxxxxxxx> wrote:

Anyway, I'll print a photo at 100 and 300ppi, photograph it and post
it later to see what the difference is (or isn't, I accept that I may
be imagining that there is a difference in my prints).

I took this shot
http://www.pbase.com/al599/image/79058890
and printed a part of it at 480ppi, 300ppi and 100ppi. I started by
downsampling it to some particular size and 480ppi; I printed that,
then, in photoshop, downsampled by selecting bicubic resampling and
decreasing the resolution to 300, printed that, went back to the
480ppi image, downsampled to 100ppi in the same way, and printed
again. I then photographed the results at 1:2 (or closer to 1:1.9 in
fact), cropped a part, changed to srgb, and put them here:
http://www.pbase.com/al599/image/79296092/original
http://www.pbase.com/al599/image/79296094/original
http://www.pbase.com/al599/image/79296096/original
As you can see, there is a huge difference between the 100ppi and
300ppi prints (and it looks even worse in reality, believe me). The
problem is not the bicubic downsampling, on screen it looks fine (ie
no more jaggies than you'd expect). The 480ppi has some more details
(there's a fence in the crop, check that) but in reality it's not much
(but it does look crisper). I think it's a result of some
interpolation by the driver, as on screen the fence is clearly
resolved at both 300ppi and 480ppi, while on the prints the 300ppi one
is not so clearly resolved.

Anyway, if you think before posting this time, you'll see that at a
sensor length of 23.5mm (call it 1 inch) and 1:2 magnification, you'd
expect to see something like 200 image pixels along the long
dimension. That is around what I see (of course the image I linked to
is a crop, not the full frame, although I can put that there too).

So maybe we can now agree that you were wrong, and 300ppi does look
significantly better than 100ppi.

In reality, as I said, the 100ppi print looks extremely bad;
personally, I wouldn't bother with printing if that was the maximum
quality. After all, it's like a monitor. Anyway, that you claim that
100ppi is as sharp as 300ppi for inkjets tells me that either you have
never seen 100ppi prints (so you don't know how it looks like), never
seen inkjet prints (so you think they look like 100ppi prints), or
both.

Anyway. I am curious to see what you will now think of to avoid saying
you're wrong.

.

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