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

Reply
 
Thread Tools Search this Thread
Old Feb 9, 2004, 10:05 PM   #11
Senior Member
 
JerryF's Avatar
 
Join Date: Jan 2004
Posts: 149
Default I have to disagree

Quote:
Originally Posted by PKchopper
Taken from the link:

A. Many digital photos will open into your photo editing software with a resolution of 72 ppi. This is either because your digital camera does not store resolution information when it saves the photo, or the software you are using can't read the embedded resolution information.
Even before I open a pic file with any software, I can right-click (using Windows XP) and select Properties, click on the Summary tab, and select Advanced. This shows the Width and Height in pixels, the Horizonal and Vertical Resolution (which is 72 dpi), bit depth, and so on.
JerryF is offline   Reply With Quote
Old Feb 9, 2004, 10:42 PM   #12
Senior Member
 
Join Date: Dec 2003
Posts: 383
Default

JerryF,

That makes it sound even more like your camera does not imbed or relay the photo information when the file is transfered into windows.

How do you transfer the photos? via a card reader, direct USB connenction or ?

If you use your camera's direct link and not a card reader, have you tried looking at the properties of the picture while it is still in the camera to see if it registers 72 dpi?

Or if you use a card reader you should be able to look at the picture properties while the files are still on your camera media.
PKchopper is offline   Reply With Quote
Old Feb 10, 2004, 2:56 AM   #13
Moderator
 
Nagasaki's Avatar
 
Join Date: Jan 2004
Posts: 897
Default

If you take a 2Mp image you have approx 1200 x 1600 pixels. If this is displayed at 72 ppi it would be 1200/72 x 1600/72 inches (16 x 22 inches approximately). 72 ppi is the resolution of most monitors and if you select the option to view actual size and only see part of the picture this is what you are getting. If you zoom out to look at the whole picture you're still seeing 72 ppi because that's all the monitor can display but you're not seeing all the pixels because the software has to discard some information to fit the picture on the screen.

Taking the same 1200 x 1600 pixels and printing it out if you size it to 6 x 8 inches you are printing a 200 dpi. Simply because 1200/200 = 6 and 1600/200 = 8. The 72 ppi stated in the file properties only has any meaning at a specific image size.
Nagasaki is offline   Reply With Quote
Old Feb 10, 2004, 5:36 AM   #14
Senior Member
 
Alan T's Avatar
 
Join Date: Jun 2003
Location: Chester, UK
Posts: 2,980
Default

Quote:
Originally Posted by informativetoo
Who's right and who's wrong? ...So those who increase p.p.i. are doing so to have a smaller image, a smaller printed picture?
No. If they alter the dpi figure in the image file, all they do is alter the image file, invisibly and with no practical effect.

What happens next depends on the printing package. They can turn the dpi figure set on the camera or in the file to a tiny or a huge figure and it will make no difference to the printed result, because you're pretty certain to be asked what *SIZE* of print you want when you try to print it. The pixels per inch that are printed will be the number of pixels in the image divided by the size in inches. The 72 or 7.2 or 720 figure set on the camera has no effect whatever.

For a high quality printed image you need above 200 pixels per inch on the print (but can often get away with fewer if you're not fussy). But twiddling the ppi figure in your jpeg or tiff file doesn't do anything about that; it just alters a useless figure embedded uselessly in the file.

How many of your pixels there are per inch of print is set by the *SIZE* (in inches or furlongs) of print you ask for in whatever package you use to do the printing.

I suggest you just forget about dpi in your image files, and get shooting and printing.
Alan T is offline   Reply With Quote
Old Feb 10, 2004, 6:01 AM   #15
Senior Member
 
Join Date: Aug 2002
Posts: 2,162
Default

I'd also suggest you use as many pixels as possible to capture your image and put as much original pixel data as possible on your prints without throwing much away away. When you make huge prints you will soon notice that more pixels at the start, will give you similar quality to your 6X4 prints held at the same distance side by side. Although as Alan T says, the eye is fairly happy with a couple of Mpix for a 6X4 print which at the moment, is about the best that photo printers are achieving in practice.

But then if you haven't got enough pixels, you would have to sell your camera and buy a more expensive camera with more Mpix. VOX
voxmagna is offline   Reply With Quote
Old Feb 10, 2004, 3:21 PM   #16
Senior Member
 
JerryF's Avatar
 
Join Date: Jan 2004
Posts: 149
Default Card Reader

Quote:
Originally Posted by PKchopper
JerryF,

That makes it sound even more like your camera does not imbed or relay the photo information when the file is transfered into windows.

How do you transfer the photos? via a card reader, direct USB connenction or ?

If you use your camera's direct link and not a card reader, have you tried looking at the properties of the picture while it is still in the camera to see if it registers 72 dpi?

Or if you use a card reader you should be able to look at the picture properties while the files are still on your camera media.
I use a SanDisk Cardreader that is USB connected to my computer.

And yes, my last post refers to when the pics are still on the SmartMedia card. Nothing had been done to them yet. Some of the info that the pic file has is embedded by something called EXIF (Exchangeable Image File format).
JerryF is offline   Reply With Quote
Old Feb 10, 2004, 4:21 PM   #17
Senior Member
 
Join Date: Aug 2002
Posts: 2,162
Default

..............And yes, my last post refers to when the pics are still on the SmartMedia card. Nothing had been done to them yet. Some of the info that the pic file has is embedded by something called EXIF (Exchangeable Image File format)............

The EXIF header data will stay with the image file even after its been copied to your HD and can be read with a freeware package called EXIFER. EXIFER shows much more of the info than the camera.

However, the data is often 'cleaned' by photo editors when an edited pic is saved. For 'save for web' option, stripping it from the top of the file makes the web file a bit smaller and quicker to download. You have to test your editor with EXIFER to see if the data is stripped or preserved. Photoshop 7 strips most of the useful camera data and puts back its own meaningless 72/1 info but tells you the image size in case you've downsampled it. In addition it adds a whole load of PS stuff you can't read, leaving its fingerprints on all your PS edited JPEG image files.
voxmagna is offline   Reply With Quote
Old Feb 10, 2004, 5:05 PM   #18
Senior Member
 
Join Date: Oct 2003
Posts: 3,652
Default

One little practical warning in all this: since inkjets produce their best quality when the pic is resized to somewhere between 200 and 300 ppi, and since this means we need to reset the 72 ppi to 200-300 ppi, it's important to watch out for interpolation. For Photoshop, Adobe recommends turning off interpolation for that initial resizing. I don't know how the other programs do it. Maybe PSP doesn't default to interpolation, but watch out for Photoshop because it does.
bcoultry is offline   Reply With Quote
Old Feb 10, 2004, 5:48 PM   #19
Senior Member
 
JerryF's Avatar
 
Join Date: Jan 2004
Posts: 149
Default Thanks Voxmagna

for the info on EXIFER. I'll definitely try it out.
JerryF is offline   Reply With Quote
Old Feb 10, 2004, 6:20 PM   #20
twl
Junior Member
 
twl's Avatar
 
Join Date: Jan 2004
Posts: 18
Default

For what its worth I had the same concerns so, I randomly selected 26 camera models from Steves reviews (3-5 mp cameras) and downloaded a sample image. Every one was 72/1 using Photoshop7 and Exifer.

My concern was my old camera was 144, but since all of the bigger better camera show 72 I have to assume the info is not important..
twl 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 8:00 PM.