Go Back   Steve's Digicams Forums > Digital Cameras (Point and Shoot) > Fujifilm

Reply
 
Thread Tools Search this Thread
Old Jul 13, 2005, 8:23 PM   #11
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

jphess wrote:
Quote:
There are a number of different philosophies on how to resize images. I have my own way of doing it which includes increasing the resolution to 240 PPI.
That's a safe number to work with for the vast majority of printers, while still giving acceptable quality if you need to increase resolution for larger prints. But, I would not downsize for smaller prints, since the printer drivers are likely to do a better job.

If you do need to upsample images for larger prints, I'd make sure to use a good algorithm to do it. The Bicubic Algorithm in Photoshop products is fine for this purpose if you're not increasing size too much. But, if you're trying to do too much resampling, you're better off doing in steps (i.e,. 10% up, another 10% up, etc.).

Although YMMV depending on version since the algorithms are getting better with one pass upsizing.

Depending on subject type, I'll try a few different algorithms to see what works best. Most of the time, I use the free Irfanview for this purpose (see http://www.irfanview.com for download links, and make sure to download the free plugins, too). You'll find the resize/resample algorithms under Image, Resize/Resample. I use either B-Spline (Bicubic) or Lanzcos most of the time. It's also a great tool for resizing images in batch mode, and it works extremely fast.

Quote:
You probably already know this, but the native resolution for JPEG images from the 5100 is 72 PPI.
No. That's not the way it works.

You're just looking at a dpi number in the header of the image file that has nothing to do with Pixels Per Inch. It's only a a value being stored in the image header (that can be changed to any other value without impacting the image). The vast majority of printing software ignores this number entirely.

The pixel density being used for printing purposes in pixels per inch (theimportant part) is computed by dividingeach image side's resolution by the size in inches you're printing at.

For example, your Fuji S5100 produces an image size of 2272 x 1704 in it's highest resolution mode. Afterafter croppingfor the correct aspect ratio of 3:2 (ratio of width to height) for a 6"x4" print, you'd have an image size of approximately 2272 x 1516 pixels.

So, at a 6x4" print size after cropping, you'd have approximately 379 pixels per inch: 2282 pixels / 6 inches~= 379 ppi (pixels per inch)OR 1516 pixels / 4 inches ~= 379 ppi.

So, I would not resample this image after cropping (you've got plenty of pixel density for this print size).

If you wanted to print at an 10 x 8" print size, then you'd want to cropthe original image size to approximately 2130 x 1704 for the correct ratio of width to height.

This would work out to approximately 213 pixels per inch (2130 pixels / 10 inches = 213 ppi OR 1704 pixels/ 8 inches = 213 pixels per inch).

That's also probably close enough so that most people couldn't tell the difference at typical viewing sizes from most printers (although you could resample it higher if desired). Just keep in mind that resampling degrades an image (so, the printer drive may do a better job when you're this close to the desired ppi).

So, I probably would not worry about resizing an image (other than cropping for the correct aspect ratio for the print size desired) unless you were printing at larger than 8x10" sizes with this camera model (or you needed to crop an image for composition which reduces it's resolution).

This is a common misconception (that the 72 dpi value you see in the image header is the resolution you're printing at). The vastmajority of software ignores it. It's only a value stored in the image header and has nothing to do with the pixel density (which controls quality) being sent to the printer. Also, if you try to change this value (and have any resampling boxes checked), you can degrade the original image (you should not resample unless needed).

See this article for more info on how this works:

http://www.photo.co.nz/faq/resolution.htm

JimC is offline   Reply With Quote
Old Jul 13, 2005, 8:55 PM   #12
Senior Member
 
Join Date: Oct 2003
Posts: 112
Default

Wow! Lots of info that is way over the top for me.....I am very dense when it comes to this digital stuff!

I shot pictures tonight at 100 speed and 200 speed. They look much better. Back to the nice crisp pictures.

I don't understand the resizing at all. But luckily I always make a copy of my files and then play with those. I did play around with the noise reduction and that helped with some that were taken with the best light. The pictures I guess aren't super terrible. But not as nice as others The action in them is amazing!

Would having more mega pix. help with the grain situation? this camera only has 4 MP I never worried about it because of the zoom. But does that only help with cropping? but not the speed or not so much the speed but the graininess?

I haven't had any problems in the past cropping my pictures, always happy with the end results.

I do really thank everyone for their input!
spinning is offline   Reply With Quote
Old Jul 13, 2005, 9:27 PM   #13
Senior Member
 
Join Date: May 2005
Posts: 1,063
Default

JimC,

To a certain extent, I agree with you. The PPI that is displayed is simply from the header file of the image. The header file for a RAW image from the same camera is displayed at 240 PPI. However, I do routinely resample my images so that, whatever size print I am going to make, I am printing at 240 PPI, and I consistently get satisfactory results. Some people who do not like to resample the way I do, but I have decided that (for me, at least) I get the quality I am looking for. Apologize for the misstatement.
jphess is offline   Reply With Quote
Old Jul 14, 2005, 9:32 AM   #14
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

240PPI is a popular number. One reason is because Epson Printers print at a DPI that is evenly divisible by 240. For example 1440dpi is evenly divisible by 240.

So, the theory is that this is a better match to Epson's own interpolation algorithms (if you're using an Epson Printer). But, it may not be the best number for other printers.

Mike Chaney (author of QImage Pro) has a pretty good article on this issue here (that touches on this, but doesn't go into a lot of detail about why).

http://www.steves-digicams.com/techc...uary_2005.html

As a general rule, I never downsize an image for printing (since it's likely the printer drivers will do a better job of it). IOW, I'm not going to downsize a 5 Megapixel Image so that it works outto a pixel density of240PPI if I'm printing a 4x6" print. LOL

But, even Mike (and he's an expert in this area) says that if you downsize for some printer types, you can get better results (provided you are matching the native resolution of the printer). I don't look at my prints with a loupe, so I doubt the downsizing makes a lot of difference on *most* printer types.

But, if I'm printing at larger sizes, depending on the end use (and where it will be printed), I'll sometimes interpolate to a higher resolution.

BTW, Mike Chaney's QImage Pro is designed to optimize the resolution of the image to the printer being used (taking the printer's native resolution into consideration for the best match), for the desired print size, using relatively sophisticated interpolation algorithms.

If you do a lot of printing, you may want to check it out:

http://www.ddisoftware.com/qimage/

JimC is offline   Reply With Quote
Old Jul 14, 2005, 11:05 AM   #15
Senior Member
 
Join Date: May 2005
Posts: 1,063
Default

Thank you for that information. Actually, however, I don't do a lot of my own printing any more. Although I cannot see a difference in quality between my pictures that I print and the ones I outsource, I just don't get the big thrill from printing my own. Especially when I have a bigger printing job, like 76 images recently, it's just less expensive to send them to an online lab to be printed, and then just go pick them up an hour later.

Another service that I have enjoyed using is mypublisher.com. They print images on very heavy, archival paper, and bind them in a hardcover book. Their service is only for Windows users, and they have no plans to accommodate the Mac. They have some interesting specifications for their images. If you want full page prints they specify the images should be 2040x1530 px at 180 PPI. Now, I will admit that I am not an expert in this area by any means. And I might be doing something wrong. But I use the resizing tools in Photoshop to make my images meet their specifications. That probably means some upsizing, or downsizing, I don't know. But I do know that the books I get back from them are very impressive. So my approach might be wrong, but I'm happy with my results. I appreciate your comments. I'm always trying to learn.
jphess 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 7:50 PM.