I have a canon rebel xti at the best quality it only does 72 dpi. Does anyone know how to make it 300dpi?

Question

But what If i want to print big? It comes into the computer off the camera as 54in x 36in. But ever site I try to get big prints from will not let me do it because of the 72 dpi. One even said I had 22dpi on a pic but in Photoshop it said I had 72.

Answer 1

You can't alter the camera software, but the good news is - it doesn't make any difference. I wrote this for a specific question, but it seems like 99% of it would apply to your question, so here you go:

Resolution - PPI - DPI

The easiest way to find out what you have is to take a picture.
Open the picture in Photoshop or Photoshop Elements.
Click on "Image" then "Resize" then "Image Size"
(Or use [CTRL]+[ALT]+[I] < Look at "Resolution" on the window that opens and it will show you what the resolution of the image is.

You can not control the pixels per inch in your camera, as this is a function of the sensor. I have found the following ppi for SOME cameras by the following manufacturers. I wonder if this specification is available anywhere. I have four camera manuals in front of me and I can't find it in any of them.

NIKON - 300 ppi
CANON - 180 ppi
PENTAX - 72 ppi

We "discussed" this by way of question and answers a while back and decided that the ppi file produced by the camera really did not have any effect on the capability to produce a good print. If I take a photo with my wife's 6 MP Nikon and view the image on the screen, it will start out as 300 ppi. If it's a full frame image of 3008 pixels x 2000 pixels, the SCREEN image would be pretty big if I viewed it full sized, but it would print 10.0" x 6.6". If you crop a 5x7 out of this, keeping it as full-frame as possible, it becomes 400 dpi.

With my brother's 6 MP Pentax, the image is 2816 px x 2112 px, but it's at 72 ppi. If you print this without cropping, it would be 39" x 29"!!! If you crop a 5x7 out of this, though, it becomes 402 dpi resolution, which is virtually identical for the Nikon 6 MP camera.

With my son's 6 MP Canon Powershot A620, the image is 3072 px x 2304 px, but it's at 180 ppi. If you could possibly print this without cropping, it would be 17.1" x 12.8". If you crop a 5x7 out of this, though, it becomes 439 dpi resolution, which is a bit better than either of the other 6 MP cameras.

In other words, regardless of the sensor's pixel-per-inch output, 6 MP cameras produced the same resolution when it came time to print comparable images. How about a camera with more pixels?

If I take a photo with my 10 MP Nikon D200 and view the image on the screen, it will start out as 300 ppi. If it's a full frame image of 3872 pixels x 2592 pixels, the SCREEN image would be pretty big if I viewed it full sized, but it would print 12.9" x 8.6", if I had the right paper. If you crop a 5x7 out of this, keeping it as full-frame as possible, it becomes 516 dpi, or higher resolution than the 6 MP cameras. We knew that is would work out like this, though, didn't we?

The REAL question is, what difference does this make in the real world? If we agree that 300 dpi is an excellent resolution for prints, as long as you end up with at least 300 ppi after you are done cropping on the screen, you will get an excellent print as far as resolution goes. All four cameras exceed that amount. I usually resize "down" to 300 dpi before printing, because you can't tell the difference above that resolution anyway. Most people would be quite happy with a 200 dpi print, so go ahead and crop a bit. If you get a print resolution too much below 200 dpi, you will start to see digital artifact in the print and it will be objectionable.

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So, if your goal is an excellent print with dots that are small enough that they are no longer distinguishable as individual dots without magnification, you need to print at 300 dpi. You can go down in resolution to 200 dpi and still have satifcatory results. The resolution of 200 or 300 dpi is NOT a function of the camera beyond the degree that I have discussed above. It is determined by the software you are editting your pictures with and you usually have enough size to work with using any camera at or above 6 MP to get decent pictures.

Working this out is easy once you understand the concept of print resolution. If you want 300 dpi, just do the math.

4" x 6"
4 inches x 300 dots per inch = 1,200 dots
6 inches x 300 dots per inch = 1,800 dots
1,200 dots x 1,800 dots = 2,160,000 dots or 2.2 MP

5" x 7"
5 inches x 300 dots per inch = 1,500 dots
7 inches x 300 dots per inch = 2,100 dots
1,500 dots x 2,100 dots = 3,150,000 dots or 3.2 MP

8" x 10"
8 inches x 300 dots per inch = 2,400 dots
10 inches x 300 dots per inch = 3,000 dots
2,400 dots x 3,000 dots = 7,200,000 dots or 7.2 MP

I will let you substitute 200 for 300 and do the math on these charts to see what the minimum acceptable resolutions for the various sizes would be.

4" x 6" - 960,000
5" x 7" - 1,400,000
8" x 10" - 3,200,00

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ADD'L FOR MIKE
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What Nikon camera gives you 72 ppi? I've never seen anything but 300 ppi from Nikon for the past 5 years.

You say that I am focused on the wrong situation, but it just depends on which end you are examining the problem from. Maybe my use of the term "crop" is misleading, but that's what I'll call it. If you take a full frame image and select the full frame with the 5x7 crop tool, for instance, you are reducing the full frame (or most of it) to 5x7. That's exactly what you are talking about. I'm not claiming super resolution, but only saying exactly what you said - if you downsize a large image to a printable size, you will find that the resolution in all camera systems is virtually the same. They are just calling the same thing a different name. If this was not the case, Pentax would lose in the resolution war with 72 ppi and they would never sell another camera. I don't understand why this measurement is not standardized, but I don't know anything about camera design either.

Answer 2

The manual is available for down load here
http://alpha02u.c-wss.com/inc/ApplServlet?SV=WWUCA900
Page 60 shows how to set the image size/quality and you can change the actual pixels per inch by selecting print size or editing.

The other guy's argument is focused on the wrong situation. He wants to crop a large image down and claims a huge high resolution image is just as good as a small low resolution image, but he fails to mention that the big image can be reduced in size without cropping with an increase in resolution. If I take an image that is 1024 x 768, in Paint Shop Pro, which I use, I can change the 72 dpi that it comes out of my Nikon camera for a 14.2" x 10.7" image and change it to 300 dpi (in a smaller 3.4x2.5" image) then all the detail of the large image is in the smaller. On the other hand, if I take a small 72 dpi image and try to print it big, instead of seeing detail, I will see the edges of the pixels as little squares.
In fact, what I do with most of my images is crop them as needed then reduce them by 50% in each dimension for use on the web while saving space.

Answer 3

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Answer 4

shoot in the raw mode