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Old Jan 19, 2004, 1:09 PM   #1
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Default Finding the higher PPI digitals for photo printing


Just tested a Canon Digital Rebel and discovers that it is hard-set to 72 ppi as max. Can anybody recommend a digital camera in the same price range ($1k) that has better resoluton/higher PPI? Would like 300 PPI or better for photo prints.


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Old Jan 19, 2004, 2:44 PM   #2
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Default Re: Finding the higher PPI digitals for photo printing

Originally Posted by jimrousey

Just tested a Canon Digital Rebel and discovers that it is hard-set to 72 ppi as max. Can anybody recommend a digital camera in the same price range ($1k) that has better resoluton/higher PPI? Would like 300 PPI or better for photo prints.


Jim, This is a common misconception. The cameras don't take photos at 72dpi by default -- that's just how your software is displaying them (it's a size that most image editing packages have standardized on, even though most monitors use a display resolution that's slightly higher).

For example: A typical photo will be taken at around 2560 x 1920 pixels with most 5MP models (your 6 Megapixel Canon Digital Rebel is actually more than this, at 3072 x 2048 pixels).

So, with a typical 5MP Digicam, if you are displaying an image with software, at 72dpi, you get a very large image size on screen (2560/72ppi = 35.555 inches, 1920/72 ppi = 26.666 inches). So, on an older model monitor (as the 72dpi display standard was supposedly based on), a 2560x1920 pixel image would appear to be around 36 x 26 inches large (with monitor size/resolution entering the equation, too).

But, when you send this same image to a printer, the pixels per inch sent, depend on the print size.

For example: if you wanted the "perfect" 300 pixel per inch print , a 2560 x 1920 image would translate to an 8.53" x 6.4" print (2560 pixels/300 = 8.53, 1920 pixels/300 = 6.4).

Your Canon uses a slightly large image size than most other digicams in it's price range, at 3072 x 2048. So, at 300 pixels per inch, this translates to a print size of 10.24" x 6.8".

However, most users won't see any difference between 200ppi and 300ppi (unless you look at the photo under magnification).

The printer driver should use all of the resolution (as long as you don't have any resize/resample boxes checked).

Actually, what it's really doing, is taking the image you send it, then converting it again, into the actual DPI printed by the printer model. It knows nothing about what your software is displaying it at -- only the actual resolution of the image in pixels (around 2560 x 1920, in the case of many 5MP models).

If you are using a 3rd party printing service, ask them how many Pixels Per Inch (minimum) is needed for the desired print sizes (most don't even care, with the printer software automatically interpolating -- but for very large print sizes, this can be a problem with some printer types).

As far as print sizes, many will argue that 150 pixels per inch is plenty of resolution, with anything more a waste, since the human eye won't be able to tell the difference at normal viewing distances.

Others will argue that 200, or even 300 pixels per inch is necessary for the best quality. Again, I've found 200PPI to be plenty.

Here's a chart that may help. You'll probably find that the "good" column is all you need (unless you're going to examine the print under magnification). You Canon Digital Rebel has an image size of 3072 x 2048 pixels.


IMO, anything above about 180PPI is fine for prints up to 8x10", and even less is can be used for larger prints (because you'll be viewing them from further away). The printer used can make a difference, too -- as many ink jet printers "optimize" the input they receive for photos. Dye Sub printers may require more pixels (300 ppi is best for some dye sub printers).

Here's another chart that takes popular digital camera image sizes, and shows how many pixels per inch you'll be sending to the printer driver for popular print sizes:

Also, you can interpolate an image using software (you shouldn't need to, unless you are printing VERY LARGE prints). This does not increase the detail captured originally, but it does add pixels (based on the value of adjacent pixels). This lets you print larger images without pixelaton.

A good free package is irfanview. It has a very sophisticated Lanczos Filter based interpolation algorithm (you'll find this option under the resize/resample menu option). You can download the software (free) from this link:


Also, you may want to be aware that standard print sizes can result in cropping of your digital image. Refer to this chart, to determine the percentage of your image that will be used, at popular digital camera sizes, for standard prints:


Some printing services (like Photoaccess.com) offer "digital size" prints (no cropping of your photos). Others don't. So, you may want to crop your photos for standard 4x6" prints. But, don't mess around with DPI count (or check any resize/resample option boxes). More resolution than needed is fine to send to a printer.

Now, there is a flag for dpi in the image header, but Changing it is only changing a byte in the image header and doesn't really change the image at all. But, I'd advise to never try and change this setting with Image Editing Software, as some software may try to resize an image based on this flag. Printing software ignores it.

The ONLY current model Digital Camera anywhere close to the price of your Canon Digital Rebel with higher resolution is the brand new Sony DSC-F828 (it's 8 Megapixels).

However, it's tiny sensor will have higher noise than the dramatically larger sensor in your Canon (your Canon is in a separate class).

To do much better (without unwanted noise, and ability to use higher ISO speeds), you'll need to step up to the Canon EOS-1DS (11 Megapixels).

Just bear in mind that it takes 4 times the resolution to double the image size (because resolution is composed of width x height). So, unless you're planning on very large prints, the extra cost may not be worth it (the EOS-1DS is selling for around $8,000.00 -- camera body only -- no lens).
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Old Jan 19, 2004, 2:59 PM   #3
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P.S. - Kodak does have a 14 Megapixel Model (DSC-14N) that you can get for around $5,000.00. However, I think you'll find that it's a terrible performer in low light, at higher ISO speeds. It's more suitable for studio work.

IMO, you've got the best "bang for the buck" camera already (resolution, dynamic range, low light performance at higher ISO speeds).

To do much better, you'll need to spend a LOT of money.
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