Go Back   Steve's Digicams Forums > Digicam Help > General Discussion

Reply
 
Thread Tools Search this Thread
Old Aug 10, 2003, 5:46 PM   #1
Junior Member
 
Join Date: Aug 2003
Posts: 6
Default lower the ppi or use interpolation?

im pretty new at this so i dont know what produces better results, i am using PS7. i have a 2048 x 1536 image at 300 ppi. it can produce like a 5 x 6.8 picture with no interpolation. i need to get this image up to 8 x 10. should i lower the ppi until it reaches 8 x 10? or should i use bicubic interpolation to get it up to 8 x 10? which 1 of these ways will get me the best results?
newtothis is offline   Reply With Quote
Sponsored Links
Old Aug 10, 2003, 7:29 PM   #2
Senior Member
 
Join Date: Oct 2002
Posts: 544
Default

Just print the picture... your camera will produce an 8 X 10 with no problem. Don't re-sample... don't do anything to your picture file. Set the printer to match the paper type (use a good quality photo paper), and best quality available on your printer driver. Bet it'll look just fine. Your 300dpi standard is nice to have, but not really necessary.

I use Genuine Fractals to "rez up" pictures from my 2.6 MP Powershot Pro90 when I want to print Super A3 (13 X 19) photos. The pictures look fine, all the way down to about 180dpi.
Wildman is offline   Reply With Quote
Old Aug 10, 2003, 7:57 PM   #3
Junior Member
 
Join Date: Aug 2003
Posts: 6
Default

i have to do 1 of them because i print from PS7. if i just send the picture on it's way it will print out at 5 x 6.8. i have to use 1 of the 2 methods i mentioned to bump it up tp 8 x 10 first. i just dont know which looks best.
newtothis is offline   Reply With Quote
Old Aug 10, 2003, 9:11 PM   #4
Senior Member
 
Join Date: Aug 2002
Posts: 1,910
Default

By using interpolation you are adding information to the picture that wasn't there originally, IOW distorting it. Lower the DPI to get a larger picture.

With my 2mp camera (1600x1200) I do 8x10s all the time and they're fine at 150dpi
Mike_PEAT is offline   Reply With Quote
Old Aug 11, 2003, 1:38 AM   #5
Senior Member
 
Alan T's Avatar
 
Join Date: Jun 2003
Location: Chester, UK
Posts: 2,980
Default Re: lower the ppi or use interpolation?

Quote:
Originally Posted by newtothis
i have a 2048 x 1536 image at 300 ppi
What's not obvious to many people is that the "300ppi" may well be embedded in the camera or computer file, but it's meaningful only to output packages like printer drivers and image viewers, and many of them ignore it or make little use of it.

The only real data in the image file that affects the output quality is the 2048x1536 pixels and their properties.
Alan T is offline   Reply With Quote
Old Aug 11, 2003, 5:01 AM   #6
Senior Member
 
Join Date: Aug 2002
Posts: 2,162
Default

............The only real data in the image file that affects the output quality is the 2048x1536 pixels and their properties............

That's nearly true - you can't put something back that you didn't have to start with.

However, the human eye is capable of being fooled by visual masking techniques, a principle used in the acquired JPEG (which no longer becomes 'real data'), to the final print.

The question Newtothis is really asking, is out of all the techniques for enhancing an image so that a larger size looks as good as the native print (and even a JPEG isn't native), which technique is best. He probably isn't aware that whilst genuine fractals is very good, it's a time consuming process for 30 prints! so workflow is a factor. Noise reduction is the same - 1 or 2 special prints can be worth the effort.

Unless somebody comes back with a serious objection, I'd suggest for 10X8 (compared to 6X4) first trust the printer to do a reasonable job of image enhancement. That's what it's designed to do. If you want to spend more time on a 1 off, try other methods by cropping a small area of the original and working with that. Nobody has mentioned the variable detail in scenes which can affect the enhancement method used. It's like in-camera sharpening, built in printer enhancement should work most of the time, when it doesn't - try something special.

The only time I might consider re-sampling to actual size, is if I was sending a file to an online photo printer - and I didn't know how good it might be at re-sampling the image, also if you are sharpening or noise reducing an image, you should really be checking at the output resolution. Otherwise, what you see isn't always what you get!

Rather than worry about the output decision, you'll get more gain by concentrating on camera techniques and the factors in acquiring a clean image which will give better large prints.
voxmagna is offline   Reply With Quote
Old Aug 11, 2003, 6:21 AM   #7
Member
 
Join Date: May 2003
Posts: 45
Default

If you have a decent printer, then lower the ppi in ps7 till you have your 10 x 8. You only need 300 ppi if your producing a colour spread in a mag. Far too many people think you have to print every thing at 300 ppi. You dont. There is no difference in quality between 200 ppi and 300 ppi on the average home printer . Dont believe me. Try it.
David Elson is offline   Reply With Quote
Old Aug 11, 2003, 8:02 AM   #8
Senior Member
 
Join Date: Aug 2002
Posts: 2,162
Default

David is right. The real reason though, is because most people don't use the original manufacture's ink and glossy photo paper. I once did some research and microscopy on different oem inks and papers. In most cases the dot bleed is sufficient to reduce the resolution - Except when using say Epson consumables in their printer. This isn't an advert! but I know what I saw and measured.

If you want to do your own test, get a 30X pocket microscope. Print some test pics at different resolutions. When you can't see any white space between the dots - you've maxed out on your ink/paper combination!
voxmagna 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 2:41 PM.