# Need help setting DPI on Canon 350D



## sothardw (Jan 31, 2007)

Hey all, I just got a Canon Rebel XT.  I have looked through the manual many times, but I am not sure how to change the DPI.  I am taking photos at 
3456 x 2304 and only getting 72 DPI.  So there is no clarity when I zoom in on  a photo.

Can anyone lead me in the right direction?

Thanks all!


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## shingfan (Jan 31, 2007)

the definition of DPI is dots per inch....so depending on how much you are zooming...you get different DPI.....you change DPI when you zoom into different depth......you wont expect a clear image when you zoom all the way in....is very obvious because the DPI is less........if you want higher DPI....you just zoom out....

zoom in = lower DPI
zoom out = higher DPI

but honestly...DPI is something that you use on printer........on your camera....you are limited by the resolution of the LCD display...and it is fixed all the time...but you can understand DPI in a similar manner and it does work on the LCD screen in a similar manner even though it is not exactly the same


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## auer1816 (Jan 31, 2007)

He's right, DPI has nothing to do with your digital picture or the quality on screen or on the camera's LCD, just the print.  72 DPI is just what cameras output -- can't change that.


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## c_mac (Jan 31, 2007)

i think he means the PPI (pixels per inch). a standard JPEG at least on most DSLR's is 72. now i know that some are 180, but obviously your's is 72. your best option is to either shoot in raw or change the resolution thus bumping up your PPI. if doing this in photoshop make sure that the resample image box in un-checked. change the PPI and the resolution will change accordingly


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## Big Mike (Jan 31, 2007)

That's right...DPI is a printer setting and really has nothing to do with the camera and little to do with the digital file.

PPI (pixels per inch) is the display size on the computer screen.  72 is used because that's plenty for viewing an image on the screen.  You can change your PPI to 10,000 or change it to 3....it won't necessarily change the image at all...it will just change it's 'size on the screen'. (unless you resample the image at the same time).

The important part is the actual size of the image in pixels (3456 x 2304)...that's all you should concern yourself with for now.

Pixels per inch becomes important when you are deciding what size you want to print the image.  Most labs will want 300 pixels per inch of print size.  So if you want to print a 4x6, then you will need at least 1200x1800.  If you want an 8x10, then you will want to and image that is 2400x3000.


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## sothardw (Feb 1, 2007)

Thanks all! That cleared it up for me.  I was confused on the terminology there and the representation of the terminology.  I need to start reading some books.  I just got my first non-point and shoot camera, so I am new to being able to adjust everything.

Talking about the zoom makes sense, I was using a Macro lens.

Also, I was looking at my manual for my camera, and it shows lots of options that I do not have in my menus.  I don't have the ability to shoot and RAW format.  Any ideas there?

Thanks again all!


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## Big Mike (Feb 1, 2007)

> I don't have the ability to shoot and RAW format. Any ideas there?


With that camera, I don't think that you can set it to record RAW files...while you are in full auto mode.  Switch it to one of the 'creative zone' modes P, Av, Tv or M.  This is not laid out in the manual very well...you are certainly not the first person to ask about this.

Many people, with their first DSLR also ask about the DPI/PPI etc. as well...so you are not alone.


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## markc (Feb 1, 2007)

Big Mike said:


> You can change your PPI to 10,000 or change it to 3....it won't necessarily change the image at all...it will just change it's 'size on the screen'. (unless you resample the image at the same time)


It won't even do that. Screen resolution determines how much room those pixels will take up. A screen that is 17" wide at 1280 pixels is 75 PPI. A screen that is 17" wide at 800 pixels is 47 PPI. The pixels of the image are forced into that resolution.

The embedded PPI or DPI doesn't do anything as far as I can tell. It's just there as a handy piece of info. The number of pixels is the determining factor for how it's viewed on the screen (combined with screen resolution), and print size is the determining factor for making a print. DPI is just a handy guide to tell you what the quality will be like for a print of that given size.


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## sothardw (Feb 1, 2007)

My main reason for asking about DPI/PPI was for when I do photoshop work.  I am able to have more defined effects when I use an image with higher level of DPI/PPI.  I will just try taking a HUGE photo and then go into photo shop with a re-size to shrink the image.  That probably doesn't sound right, I just am not that great at typing out what I mean to explain.


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## Big Mike (Feb 1, 2007)

> It won't even do that


I though it sounded weird when I typed it... 



> My main reason for asking about DPI/PPI was for when I do photoshop work. I am able to have more defined effects when I use an image with higher level of DPI/PPI. I will just try taking a HUGE photo and then go into photo shop with a re-size to shrink the image. That probably doesn't sound right, I just am not that great at typing out what I mean to explain.


Just always use your camera's maximum resolution setting.  I also suggest shooting RAW...but that's a slightly different issue.  Do your Photoshop work with the image at that size...and then, if you need/want to...change the size for whatever specific purpose you want to.  

When I'm done with an image...I often end up with several different copies of it.  One is the original, another is the Photoshop working copy (with layers etc.)...then I might make a copies for certain print sizes and aspect ratios...then I might shrink and downsize the image and save a copy for uploading to the web.


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## markc (Feb 1, 2007)

No really. DPI/PPI has no meaning when you are dealing with a digital file, only the number of pixels. PPI/DPI only deals with display or printing, not the file data itself.
http://www.rideau-info.com/genealogy/digital/dpi.html
There are some printing labs that require 300 DPI because of the equipment they use, but if you are using an inkjet, that can be ignored.


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## Digital Disasta (Feb 1, 2007)

Ok, well DPI and PPI are related in the fact that when you are working in a imaging program it is considered PPI, when you are printing it is DPI.  If you plan on printing these images, 300 should be the min. resolution, when I work with print for work, it's 600 DPI.  Now, when you are taking images with your camera, and it has a setting for DPI/PPI, exporting the image might be a problem (im not sure), but, if you import to an imaging program at 72 PPI, and try to make it 300 for print, it's going to be extremly distorted.  So if you have a setting on your camera for resolution put it to at least 300 (if you plan to print), you wont see the difference on the screen (because screen resoultion is 72 PPI), but it will ensure the picture to be a quality one.

The website markc posted is wrong, don't listen to it.  I will prove it now.

Goto google, click on images.  (the reason for this is because most of the images found on the website are web images (72 dpi)

Search for anything get the full image, and copy the image to the clipboard.

Next open up Photoshop, hit apple+N, (cntl+N windows)

Now since the image is in the clipboard the image size is already set for photoshop, hit ok.

When the .psd is open paste the image apple+V (cntl+V windows)

next goto Image>Image size.

Change the DPI setting to 10.

Look at the image...

Now go back to Image>Image size, and make it 300.

look at the image at 100% and tell me that doesn't look like sh!t.

Then, try to print it, lol, looks like colored mud all over the page.

PPI/DPI matters A LOT.


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## markc (Feb 1, 2007)

You are probably resampling. Try it with with resample off. If you have it on, you are changing the actual number of pixels. That's what determines what you are seeing. If you have resampling off, you leave the number of pixels alone and only change print size and DPI. You can change the DPI all you want and it won't change the image, only the size the print will be.


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## Big Mike (Feb 1, 2007)

I believe Mark is correct.  What Mr. Disasta is doing is trying to re-sample a small image into a bigger image...basically trying to create pixels...which will cause a loss in quality.

The most important thing is the actual size (in pixels) of the image....not the DPI or PPI.

Try this...open any image in photoshop and open the image size box.  Deselect the 'resample' box and change the PPI.  Change it to 10,000...or change it to 10...it won't change the image.


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## Digital Disasta (Feb 1, 2007)

Big Mike said:


> I believe Mark is correct. What Mr. Disasta is doing is trying to re-sample a small image into a bigger image...basically trying to create pixels...which will cause a loss in quality.
> 
> The most important thing is the actual size (in pixels) of the image....not the DPI or PPI.
> 
> Try this...open any image in photoshop and open the image size box. Deselect the 'resample' box and change the PPI. Change it to 10,000...or change it to 10...it won't change the image.



Turning resampling off and changing the DPI will change the image size when printing, just look at the dementions in the boxes, or turn the rulers on and change it is 72, or 300, the size changes...now I'm kind of confused on what the topic was originally about...haha


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## Big Mike (Feb 1, 2007)

Yes...when you change the PPI...it does change the 'size in inches'...but that's a different issue (at least I think it is...I forget what we were talking about too).  If you want to know the print size...then change the PPI to 300...and it will divide the image size (in pixels) by the PPI and give you the print size.

It's up to you to know that for good quality prints...300 pixels per inch is what you want to shoot for...but it all comes back to the size of the image.


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## markc (Feb 1, 2007)

The point I was getting at is that size of image in pixels, size of image output (either screen or print), and DPI/PPI are tied together in a similar manner as ISO, aperture, and shutter speed. DPI/PPI alone tells you nothing about the quality of an image without knowing the rest of the story, just like knowing just the aperture doesn't tell you what an image's exposure is.

Actually, it's even less important than one of the exposure elements. DPI/PPI is made up of the other two image elements: Dot/pixels and inches. It's just telling you how many dots/pixels there are in an inch.

When a image is in a digital file format, the only element that has bearing is number of pixels. There are no inches, so the other two elements mean nothing. When it's put on a screen, they now have bearing, but the number of inches changes depending on what system the image is being displayed on (size of monitor and it's current resolution), so they don't mean much. When you make a print, you finally have a solid "inch" measurement that isn't going to change on you. Now you can use the PPI to see if you are likely to get a quality image. If it's 300 PPI or more, you are likely to be happy with it. If it's 125-300 DPI, it's going to depend on your tolerance for such things. Under 125 DPI and some people are likely to have issues with the quality. That's just a rule of thumb, though. It all depends on what you are printing on, the image, your eye, and other factors.


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## Digital Matt (Feb 1, 2007)

I think the original poster was confused in thinking that the  72 DPI in the jpg from the XT meant that it was a low res file.

Dpi is meaningless, until you want to print your file, in which case you should be resampling the image to the desired image size, and setting the DPI to 300 DPI at this time.  This all should take place in software.


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## Big Mike (Feb 1, 2007)

> I think the original poster was confused in thinking that the 72 DPI in the jpg from the XT meant that it was a low res file.


We see this often...a lot of people are confused by it.


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## markc (Feb 1, 2007)

Digital Matt said:


> in which case you should be resampling the image to the desired image size, and setting the DPI to 300 DPI at this time.



I usually disagree with this approach, as it either bloats the file size without adding detail (if you are enlarging), or you are deleting detail (if you are shrinking). The only time I think it's warranted is if the printer being used actually requires a 300 DPI file to print correctly.

I've seen people talk about staged enlarging, but I remain unconvinced, as I haven't seen any good examples yet.


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## shingfan (Feb 1, 2007)

markc said:


> I usually disagree with this approach, as it either bloats the file size without adding detail (if you are enlarging), or you are deleting detail (if you are shrinking). The only time I think it's warranted is if the printer being used actually requires a 300 DPI file to print correctly.
> 
> I've seen people talk about staged enlarging, but I remain unconvinced, as I haven't seen any good examples yet.


 
i'm not sure if you alwys need exact 300 DPI image...but for sure with walmart.....if your image is 10MP and you want to print 4x6...better size it down before taking it for print.....they dotn come out nice fi you give them full size 10MP pictures...done it 3 times with full size and got poor quality...... next time i'll resize (regretting)


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## RacePhoto (Feb 3, 2007)

shingfan said:


> i'm not sure if you alwys need exact 300 DPI image...but for sure with walmart.....if your image is 10MP and you want to print 4x6...better size it down before taking it for print.....they dotn come out nice fi you give them full size 10MP pictures...done it 3 times with full size and got poor quality...... next time i'll resize (regretting)



This sounds like an interesting experiment in the making. 

You are saying that I'll get better prints by reducing the size of the image, before I take it in? Sounds counter intuitive? Why would I want to degrade an image, to make it better?

Type slow, I may have to read it more than once...


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## markc (Feb 3, 2007)

Some printing hardware requires it. Some of them, like dye-subs, print one dot per pixels. For them, DPI and PPI are the same. If you send something bigger, it has to be shrunk to match, and their software may not do as good a job as you can do at home with Photoshop. Some require it for other reasons. It's good to find out exactly what the "native" resolution of these printers are, because for some it's 360 DPI or something other than 300 DPI. You can pick up finer detail if you get it just right.

Printers like inkjets and lasers use many dots to make up a single pixel. This is why you will see things like 2400 DPI and up. That may seem like a waste if your image is only 300 PPI, but it allows that one pixel to have its own dither pattern. You don't have to rely on just having the printer pick the closest color. Many colors can be blended in that small space. Dye-sub printers use a transparent dye, so they don't need to use a half-tone.

Basically, sending a print out has different requirements from printing at home (though they may be the same if the lab uses a large inkjet). It's good to find out what equipment is being used so you can adjust for it.

Here's a couple of links you might find interesting:
http://www.shortcourses.com/how/printers/photoprinters.htm
http://www.alpenglowimaging.com/resolution.htm


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## MACollum (Feb 4, 2007)

shingfan said:


> i'm not sure if you alwys need exact 300 DPI image...but for sure with walmart.....if your image is 10MP and you want to print 4x6...better size it down before taking it for print.....they dotn come out nice fi you give them full size 10MP pictures...done it 3 times with full size and got poor quality...... next time i'll resize (regretting)


Maybe Walmart is doing their own resizing and screwing up the quality? I don't know how they do it but I know they will crop for you if the ratio is off, and their cropping software (or whatever they use to do it) will crop indiscriminately. My old Nikon Coolpix took pictures at 4.5 x 6 and I always had to crop before printing if I didn't want them messing up my pictures. This is another reason why I always crop my big picture files down to 1800 x 1200 (for a 4 x 6). I don't want them messing it up so I make sure they don't have to do any work other than printing (and they've screwed that up enough times anyway :x )


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