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Old 09-21-2004, 01:36 PM   #1
Neil
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Question re: camera type

I'm no artist but I like to take pictures to put on my website. I use a Kodak Easy Share (CX4230) 2 Mpixels. I usually set the camera to the lowest quality of image. When putting pics on my website I use a resolution of 76 pixels/inch. My question: for this purpose can I do better with other equipment or settings? Here's
a page with pics taken under a variety of conditions.
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Old 09-21-2004, 05:28 PM   #2
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My advice would be to take the pic at the highest resolution and then change the resolution to 72 dpi to post them on the web.

I don't use digital. I scan my photos in at 1200 dpi and save them as a tif file (No quality loss). That way if I want to enlarge the pic, I still get good quality. If I want to print it, then I save it out at 1/3 of my printer resolution (which makes the best print) and to put it on the web I reduce it to 72dpi and usually save as a jpeg at 50%.
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Old 09-22-2004, 07:37 AM   #3
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Quote:
Originally Posted by Neil
...I usually set the camera to the lowest quality of image...
Neil-
I've actually got the same camera. I use the highest quality setting, then downsize the pix if I want to post or send them. That way I've got a higher quality version if I do decide to print any of them.
I don't think you'll get better results for your purpose with a higher res camera, and I think Kodak's color fidelity is as good as anything out there. Of course if you decide to make prints in larger formats, higher resolution is better.
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Old 09-22-2004, 09:17 PM   #4
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The guys above are right. Memory sticks are relatively cheap, so use the highest resolution and if you run out of space get a bigger memory stick. The way most of these cameras get smaller images is using higher lossy compression, and that introduces artifacts into your images. You're much better off having the full quality images and then reducing them using software... it gives you more control over the whole process.

For web posting and email you don't need anything more than you currently have.
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Old 09-24-2004, 04:29 PM   #5
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If I take dig photo at 72 dpi and it's 10 inches by 10 then am I safe in assuming there are 720 x 720 pixels? And if I then save the above pic at 5 inches by 5 then do I lose 75% of the original pixels and have 360 x 360 pixels?
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Old 09-24-2004, 04:53 PM   #6
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Quote:
Originally Posted by Neil
If I take dig photo at 72 dpi and it's 10 inches by 10 then am I safe in assuming there are 720 x 720 pixels? And if I then save the above pic at 5 inches by 5 then do I lose 75% of the original pixels and have 360 x 360 pixels?
You've got the idea. Once you reduce the picture, if it's enlarged, the quality goes to hell. So take and save then at the higher resolution, edit them however you want (enlarge, crop, etc) at the high resolution. Then save a copy at 72 dpi for posting on the web.

That way if anyone wants a good copy of the pic you can email the hr to them and if you want to print, you can print at the best resolution for your printer (not necessarily the highest).

It's always best to save the hr copy of the pic as a tif so there is no resolution loss. Yhen if you want to send a copy and ned a smaller file, you can save a copy out as a jpeg and send it.
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Old 09-24-2004, 06:01 PM   #7
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My camera saves pics as jpg's. Are you saying I should convert it to a tif on my computer prior to editing it?
Next question: If my softwear says I'm at 72 dpi and that the pic is, say, 8x10 but I decide to print at 5x7 what happens to the pixels? Are they missing/removed from the print but still in the original file?
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Old 09-24-2004, 11:25 PM   #8
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Quote:
Originally Posted by Neil
My camera saves pics as jpg's. Are you saying I should convert it to a tif on my computer prior to editing it?
Next question: If my softwear says I'm at 72 dpi and that the pic is, say, 8x10 but I decide to print at 5x7 what happens to the pixels? Are they missing/removed from the print but still in the original file?
If your camera saves as jpg you won't benefit by converting to TIF.

(a bit of computerese...)

jpg uses what's called "lossy compression". When a picture is saved as a jpg image, some information is lost in order to reduce the number of bytes required to define the image. With jpg you actually can define how much quality you're willing to lose in order to squeezed your image smaller. You can set it to maximum quality and get an image that's virtually indistinguisable from the origonal... or maximum compression will result in an image that has VERY visible artifacts.

Once an image is saved as jpg... any loss in image quality is permanent (unless you retain the uncompressed origonal), hence the term "lossy compression"

TIF is different, it's a flexible protocol that can store images in a number of formats, but the most popular are Uncompressed images (identical to the origonal) or what's called "lossless compression". Lossless compression doesn't squish the files down as much as lossy compression, but it does reduce the size some (varies depending on image complexity) while retaining 100% of the origonal images information.

(end of computerese).

So basically, what I do is save all digital images to my server archive right off the camera, I don't mess with them at all, just file them away. When I need to post or email an image I load the origonal out of the archive, reduce it to whatever size is appropriate, save it as a jpg (typically set to middle level between quality and compression) and then send the tweaked file. I never overwrite the origonals (they're copy protected).

With film and slides I scan the origonal at an appropriate resolution for the image type (1200 dpi for prints on my HP flatbed scanner, 4000 dpi for slides on my Canon slide scanner) and save those images as TIF's (lossless compression). Once they're in the archive they're dealt with the same as digital images, except since they're so big (the slide images often tilt the scales at close to 100 meg apiece) you really have to process them to do much of anything outside of printing.

The key is to keep an 'unadultrated' origonal, then tweak and resize to your hearts content, just save your altered version to a different filename.
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Old 09-24-2004, 11:44 PM   #9
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Quote:
Originally Posted by Neil
My camera saves pics as jpg's. Are you saying I should convert it to a tif on my computer prior to editing it?
Next question: If my softwear says I'm at 72 dpi and that the pic is, say, 8x10 but I decide to print at 5x7 what happens to the pixels? Are they missing/removed from the print but still in the original file?
Oh yea... regarding printing. When you print you have a lot of control over how big it makes the output. If you have an image that's 72dpi, you can print it on a 300dpi printer and different software will do different things. Some will print it at 72dpi so it ends up the right size, some will print the 72dpi print at 300dpi... so it'll end up TINY. In some cases you can have it print your 72 dpi print on an entire 8.5x11 sheet (which means it's been stretched out to fit the paper). For the kind of stuff I do I've found it's more important that the size of the image (in pixels) is complimentary to the printers resolution given the size of the output print that you're shooting for.

I've got a cheapo 600dpi color inkjet here at home. If for some reason I'm printing to that, I try to have the images sized such that I've got 100 pixels of image for each inch of printed output. Say for instance my image is 640x480 pixels, I'd print that at 6" x 4" and it'd look halfway decent.

Now with my Codonics dye sublimation printer at work I shoot for at least 300pixels per inch of print output. So if I'm going to print out a full sheet image (about 7x10), I'd want an input image that was at least 2100 x 3000 pixels in size.

So when I'm thinking about the images, I'm never thinking dpi, I'm thinking pixel count. I only start thinking dpi when I'm moving it to media (printer or crt), and the dpi that counts there is the PRINTER dpi (or the screen resolution)... and how it stacks up in relation to the pixel size of your image.

jeeze that looks complicated... did I help at all? It's really pretty simple, you want your image to be big enough that it looks good when you print it or display it.

Last edited by Dave K; 09-24-2004 at 11:45 PM.. Reason: typo
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Old 09-26-2004, 11:59 AM   #10
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Lets see if I got the printing info. First, I need to know just how many pixels my image has got. THEN I decide either what kind of image quality or what size of image I want. The two are inter-dependant, right?
My saved image ''has'' 480 x 640 pixels. I want a 5x7 print. 480 pixels goes into 5 inches about 100 pixels per inch and 640 into 7 close to the same. Therefore I'm looking at a 100 dpi setting on my printing setup (printer and software). A 10 x 14 print would give me a dpi of about 50. If I want a sharper image then will I get it by scrunching all those pixels into a smaller print size? Or, if I order up a smaller print does the software eliminate the extra pixels?
At the time of printing does the printer's software alter what you ask for out of the software?
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Old 09-26-2004, 09:57 PM   #11
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Quote:
Originally Posted by Neil
Lets see if I got the printing info. First, I need to know just how many pixels my image has got. THEN I decide either what kind of image quality or what size of image I want. The two are inter-dependant, right?
My saved image ''has'' 480 x 640 pixels. I want a 5x7 print. 480 pixels goes into 5 inches about 100 pixels per inch and 640 into 7 close to the same. Therefore I'm looking at a 100 dpi setting on my printing setup (printer and software). A 10 x 14 print would give me a dpi of about 50. If I want a sharper image then will I get it by scrunching all those pixels into a smaller print size? Or, if I order up a smaller print does the software eliminate the extra pixels?
At the time of printing does the printer's software alter what you ask for out of the software?
As I understand the topic you're just about right (I'm not a publishing expert though, so no doubt there's more information to be had out there).

Input Image size (480x640 pixels) printed to a certain size output image (5x7 inches) or about 100dpi will yeild a good looking image for a printer that uses multiple dots for halftoning (say a laser printer or inkjet printer). My Dye sublimation printer can color an individual dot through the full range of a 24 bit color pixel, so I send images to it that have the same number of pixels per inch that it has dots per inch (300).

if you print a 480x640 pixel image to a 10x14 print you will end up with an image that has VERY visible pixels (low quality). Think about it this way, your printout would have 48 pixels per inch, so each pixels will be a bit more than half a millimeter. This may seem like a small value, but the human eye is perfectly capable of seeing things smaller than a tenth of a millimeter. Half a millimeter is HUGE. The dots on a 300 dpi printer are .085 millimeter, better but still visible enough that most consumer printers have gone to 600 dpi.

When you look at an image, you don't want to see ANY pixels, you want to see a continuous tone image, so if you only have 480x640 pixels to work with, you shouldn't blow the image up to the point where individual pixels are visible.

I guess as a general rule of thumb (that applies to most consumer printers), if you stick to a size that matches the ppi of the image to the dpi of the printer divided by the size of the halftone blocks the printer uses (info. you should be able to find online)... you'll always have the sharpest image the printer is capable of producing.

Here's some information on halftoning:
http://fhctech.org/fhc/imaging/halftone.htm
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Old 11-11-2004, 11:37 AM   #12
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Question for Dave K and Redhawk:
I just re-read this thread and have a question about Dick's avatar. The pic was taken with a 4 MP camera. It was reduced to 76 dpi then e-mailed to me. I cropped it, resized it then saved it at something like 80% compression. The problem was getting the file under the 9.6 k limit. When I saved it as a larger image I had to use so much compression that the image fell apart. I found the right balance between image size and file size but the avatar is small compared to the others on the forum. The only thing I can think of is that the pic contains a lot of info. What do you think?
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Old 11-11-2004, 02:40 PM   #13
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Quote:
Originally Posted by Neil
Question for Dave K and Redhawk:
I just re-read this thread and have a question about Dick's avatar. The pic was taken with a 4 MP camera. It was reduced to 76 dpi then e-mailed to me. I cropped it, resized it then saved it at something like 80% compression. The problem was getting the file under the 9.6 k limit. When I saved it as a larger image I had to use so much compression that the image fell apart. I found the right balance between image size and file size but the avatar is small compared to the others on the forum. The only thing I can think of is that the pic contains a lot of info. What do you think?
Neil email me a copy of the original and lets see what happens on this end. Tough to tell if it's anything you're doing or the image itself.

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Old 11-11-2004, 03:00 PM   #14
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I've had similar problems. What have found that works for me is, I'll reduce the image to the size I want and then in Photoshop I copy and paste it into a new blank file. When I flatten the image and save it the file is much smaller.
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Old 11-11-2004, 03:12 PM   #15
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I set the image width or height (whichever is larger by default) to the correct pixel size. Then I use the Jpeg otimizer in Paint Shop Pro, which show me the image size in kb as I change the compression number until I have the largest Minimum and then I save it.
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Old 11-11-2004, 04:05 PM   #16
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It worked! Thanks Redhawk and Neil for your work on this!
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Old 11-11-2004, 06:06 PM   #17
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It worked! Thanks Redhawk and Neil for your work on this!
Hold on, I'll give you the address to send the check to!!
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Old 11-11-2004, 06:23 PM   #18
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I have just deducted it from my shuttle service charge for transporting you to Copperas Pond...
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