Canon 40D Image Resolution

[AdaJac08]

Hello

I am working with a client (i am a designer not a photographer) and they have sent me some images they shot on a 40D. The image size is 34 x 56 with a resolution of on 72. Does this make sense.

I have not saved enough to purchase a camera at that level, so I am not sure if that is the appropriate resolution for an image coming off of that camera. It seems like (basing this on my wedding photos) that the image size is too large and the resolution is too low - compared to the 18 x 24 with 300? resolution from a 50D for my wedding.

Any thoughts for someone new to the digital camera world?

Thanks

[OsmosisStudios]

DPI is set when the camera's RAW file is opened and edited for the first time. Depending on what youre doing with it, it shouldnt be an issue.

How big is your poster going to be printed?

[fletch]

It doesn't matter one little bit what the images size and resolutoin numbers are in the file meta data. What is important is the number of pixels.

A 40D's resolution is 3888 x 2592 pixels.

You could the display this as:

54 x 36 @ 72 PPI
16.2 x 10.8 @ 240 PPI
13 x 8.6 @ 300 PPI
388.8 x 259.2 @ 10 PPI
1.2 x 0.9 @ 3000 PPI

Its the pixels that matter when it comes to digital images. The camera has just picked an arbitary number for PPI and its 72.

[AdaJac08]

image was shot and sent as JPEG. Before i even touched it the image seemed off. Checking image profile (before any adjustments whatsoever) the image was at 72 DPI.

The image is going down in size so i know it is not a problem, I just want to help the "photographer" out as they are a close friend and using a camera that is beyond their skills. I was not sure if there is any kind of setting that tells the camera to shoot a higher res RAW image vs. a large scale 72 DPI image.

[AdaJac08]

How does the PPI math work for the different image sizes?

[Doug Pardee]

Originally Posted by fletch

The camera has just picked an arbitary number for PPI and its 72.

To be picky, the number "72" isn't exactly arbitrary. The EXIF specification, section 4.6.4(A), requires that it be set to 72 for any JPEG not produced by a scanner-type device.

But since that number has no effect at all for photos, some digicam manufacturers have used other values and gotten away with it.

Anyway, like you say, all that matters is the size in pixels.

[dcclark]

The PPI setting in the file has NO bearing on anything practical. As said above, only the number of pixels matters. Any time you print (or send to an online print shop), they'll (or the software will) ask you what physical dimensions you want -- and they'll squeeze the photo's pixels into that size. The PPI setting will be completely ignored.

[fletch]

Originally Posted by AdaJac08

image was shot and sent as JPEG. Before i even touched it the image seemed off. Checking image profile (before any adjustments whatsoever) the image was at 72 DPI.

What do you mean by off. There is absolutley no way of telling the difference between the same image with the DPI field set to 72 or 300 or 1,000,000.

(Your wedding shots are probably only set to 300 as the photographer shot RAW and exported from the RAW converter with the aribiary number set to 300, not 72.)

Originally Posted by AdaJac08

The image is going down in size so i know it is not a problem, I just want to help the "photographer" out as they are a close friend and using a camera that is beyond their skills. I was not sure if there is any kind of setting that tells the camera to shoot a higher res RAW image vs. a large scale 72 DPI image.

Does the image have 3888 x 2592 pixels? If so the photographer has not done anything wrong, it is you as the designer who is missunderstanding what you have been given.

The 40D (as with most cameras, even a $50 P&S) will allow you to shoot at lower resolutions than the max. This will result in less pixels, not a different arbitary* number in the EXIF data.

*It may not be arbitary on the camera manufacters part as 72 is the standard but as far as I can tell there is no reason why that is the standard as it means absolutely didly squat.

PPI maths is very simple.

Number of pixels / size dispalyed (in inches) = Pixels per inch