"Norm Dresner" <ndrez@att.net> wrote in message
news:aQ7Fj.32131$D_3.6247@bgtnsc05-news.ops.worldnet.att.net...
[re Photoshop preview resampling inaccuracies]

> Absolutely! I zoomed in on a very small area and then flattened the
> image
> and there was absolutely no difference in the pixels I could see at that
> level. I suppose I should have guessed this when a previous experiment
> showed that the effect was dependent on the size of the image -- doing the
> same thing with a very small image produced no effect.

There are a number of effects that preview differently, depending on the
zoom. These are fairly rare, though, so it's not unusual for people to be
surprised when it happens.

> SO ... Let's see ... The images that Photoshop presents on the screen are
> all approximate because they have to be sampled at the screen
> resolution --
> which in my case is 1920x1440 or about 128 PPI. But when I print, the
> resolution is (usually) 300 PPI. Does that mean that I can zoom to, say,
> 3x
> the Fit-On-Screen magnification and see what the actual pixels that will
> be
> laid down on the paper would look like? Your 100% recommendation is
> ~4.5x
> the F-O-S magnification of 22.5%.

My recommendation would be to flatten the image temporarily, then set the
zoom to match the print size.

When you view a zoomed out preview, Photoshop saves time by resampling
first, then flattening. When you print, Photoshop does it in the opposite
order: flattens first, then resamples to the resolution required by the
printer driver.

For most images, this makes no earthly difference. A layer with a dithered
bitmap image is a common case where this can matter. As a practical matter,
if the appearance is not what you expect, 100% zoom is the most accurate
preview. If you don't want to zoom to 100 percent, flattening the image
also gets a better preview.
--
Mike Russell - www.curvemeister.com