Go Back   Steve's Digicams Forums > Software > Editors (Photoshop, Vegas, Final Cut Pro, Kdenlive, etc.)

Reply
 
Thread Tools Search this Thread
Old Jul 9, 2006, 8:54 AM   #1
Senior Member
 
Join Date: Apr 2005
Posts: 157
Default

Hello, I have had this question for a while, just got the nerve to post....Slipe mentioned something that made me go....WHAT?? (and pushed me to ask)

I know you should not resample if you do not need to... and photoshop is default on for resampling. Now when you crop to say an 8x10..and your pixel count should be enough to support the size even at 300 dpi.... it resamples?

Or asSlipe said, I should just leave the resolution box clear as Icrop..... but then I have to put in the resolution afterwards or does it do it for me?? (i guess I could try it out) but I just thoughtif I had a better understanding of it?

Does this all make sense?
dashboardgyno is offline   Reply With Quote
Sponsored Links
Old Jul 9, 2006, 2:22 PM   #2
Senior Member
 
Join Date: Oct 2003
Location: Indian Rocks Beach, FL
Posts: 4,036
Default

The statement that you shouldn't resample unless you have to leaves a lot of weasel room.

Whenever you resample the software has to rearrange all the pixels, making educated guesses what should be in spots where there weren't pixels before. It will rearrange most of the pixels unless you do a perfect 4X or ΒΌ, or some exact multiple. There isn't a lot of quality loss with a good resample filter but it shouldn't be done as an automatic part of cropping.

I strongly object to someone recommending someone to always resample to a set resolution like 300 PPI. If you are cropping for a 4 X 6 the resolution is going to come out higher than that for most images. The printer spooler has to rearrange the pixels in any case and will take whatever resolution you send it with no degradation from more than it can use.

I've run tests with all of my printers and always seem to come up with similar numbers. The point of diminishing returns is around 180 PPI. Above that there isn't very much improvement you can see. And I can't see any difference at all over 250 PPI even under a loupe. I don't normally resample if the image is over 180 PPI. Different printers might give different levels on that.

There is a difference between printer DPI and image PPI. A printer uses a lot of dots to make a pixel. Back when printers used 8 or 10 picolitre dots they used 16 dots to make a pixel. For 4 or 5 picolitre dots they used 32 dots per pixel. I haven't seen any white papers since then but have read they went to 64 dots when they went to 2 picolitre dots. The upshot is that the PPI a printer can use hasn't increased much if at all with higher resolutions associated with smaller dots. The printer doesn't always use all of those dots for each pixel, but the resolution is based on using all of them. I would guess they use the full complement of dots when they mix colors to make black.

Photoshop (or Elements) won't automatically resample. If you set the width and height you want in your crop tool it will not resample if you leave the resolution box blank. In the size box it won't resample unless you check the box for it to resample. If you crop without anything in the resolution box you can open the image size box and see what resolution you ended up with. That resolution includes all of your original pixels except those that were cropped off at the document size you selected in the crop tool.

At what point you resample is up to you. But I stick by my statement that you shouldn't resample unless you determine the result of your crop or sizing will result in a PPI that is too low. Even if the resolution is too low a resample doesn't improve the print as much as some people seem to think. Print something at 150 PPI. Then take that same 150 PPI image and resample it to 300 PPI. You won't see a lot of difference. It will look a little softer and a little smoother.

I find that a stepped interpolation gives the best results for bringing up an image with too little resolution. I increase in 5% increments but 10% works almost as well and is a lot faster. I also have Genuine Fractals and that is almost as good. Luminous Landscape recommends doing an upsample to 120% with Bicubic Smoother and then going back to 100% with Bicubic Sharper. That doesn't do a lot for me compared to just using Genuine Fractals. Some people like a resample with Bicubic Smoother better than straight Bicubic, but I find it too soft. But I don't like any resample as well as the original image as long as the resolution is 180 PPI or higher. Your results may vary.


slipe is offline   Reply With Quote
Old Jul 9, 2006, 9:06 PM   #3
Senior Member
 
jtgraphics's Avatar
 
Join Date: Jul 2002
Posts: 117
Default

Very good slipe some that did some their homework and got it right.


jtgraphics is offline   Reply With Quote
Old Jul 10, 2006, 11:36 AM   #4
DBB
Senior Member
 
Join Date: Jan 2004
Posts: 2,483
Default

slipe wrote:
Quote:
I've run tests with all of my printers and always seem to come up with similar numbers. The point of diminishing returns is around 180 PPI. Above that there isn't very much improvement you can see. And I can't see any difference at all over 250 PPI even under a loupe. I don't normally resample if the image is over 180 PPI. Different printers might give different levels on that.
This is true depending on the screening method used.

Quote:
There is a difference between printer DPI and image PPI. A printer uses a lot of dots to make a pixel. Back when printers used 8 or 10 picolitre dots they used 16 dots to make a pixel. For 4 or 5 picolitre dots they used 32 dots per pixel. I haven't seen any white papers since then but have read they went to 64 dots when they went to 2 picolitre dots. The upshot is that the PPI a printer can use hasn't increased much if at all with higher resolutions associated with smaller dots. The printer doesn't always use all of those dots for each pixel, but the resolution is based on using all of them. I would guess they use the full complement of dots when they mix colors to make black.

In todays world where people let the software decide on the screening, your remarks are accurate. But it is possible with decent software for the user to select thier own screens. This refers to the number of dots the printer uses to print out each image dot - the ppi. It is not a question of, "Today we use 64, whereas we used to use 32" (pardon the quotes)

There is far more to this question than the above simple answer. There are also other aspects that the user can choose, depending on the final destination of the image. Undercolor Removal, Undercolor Addition, (UCR and UCA) as well as GCR, ect.

If you are printing at a High Screen, anthing over 133 would qualify, then the higher the PPI the better. If you are printing using the Stochastic Screening Method, then the higher the PPI the better. In Stochastic Screeening the ppi of the image is broken into individual pixels which are printed individually - One for one.

There is much to learn about this and no simple paragraph such as I am writing will cover it. As a rule of thum your answer is just fine - especially if you choose to print on your home printer - where it is making the decisions. However, even there, is you so choose, results can be dramtically improved by doing it manually...

I recomend the GIMP line of printer software. Generally they will allow a greater flexibility in these matters than the software that comes with your printer. GIMP, BTW, is free.

Dave
DBB is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 5:01 AM.