Resolution

[jackstraw]

hey All -

hope this doesn't get confusing, I'm pretty new at digital photography, but I want to know if there is a way to change the resolution of my camera.

I have a Canon A620, a nice p/s camera. It's 7.1 MP - but that's not the resolution I'm talking about. What I mean is, all my images come out as 180 ppi. Whatever quality I shoot at (Superfine, Fine, etc.), they all come out at 180 ppi.

Is there any way to change this? Or is this a function of all p/s cameras?

Do the SLRs let you change the resolution you shoot at?

Thanks for any thoughts you have and share - I hope I asked the question correctly, and didn't confuse anyone. This whole "resolution" problem is a bit complicated to me right now...

[ben7337]

I do not know if it is possible I think I understand what you are saying but I am not sure if it makes sense. isn't that resolution like how a tv screen has 480pp or 1080pp? so you are saying all of your pics have the same number of lines or something no mater what size or quality? thats very odd. I probably do not understand.

[MindBender]

No, he's saying that no matter how he shoots that his pictures always have the same resolution... not the same dimensions.

Resolution is only important when you output to a media that can have variable resolution vs. size... eg... printing.

If you're printing you need to worry about resolution, if you're viewing on screen you only need to worry about the pixel dimensions.

Why is 180PPI causing you problems? It won't affect how things are displayed, only how they print... and if you're printing you should be using an application that has control over changing resolution settings for output so it's irrelevant. Is there some other reason you need your photos to be in a specific resolution?

Generally, I don't know that cameras often have control over resolution... depending on how you import the pictures, they will sometimes even give variable results.

The good news is that you can change resolution all you want without any problems... assuming you don't change the pixel dimensions.

Maybe if you give some more insight into what you're trying to do and why you need to change the resolution default we could offer a better answer.

Welcome to the forum, hope that helps.

[coldrain]

the 180 pixels per inch is just a setting that some software that goes on automatic pilot would use when printing. You should not be affected by that value in any sense, just do whatever you want to do with your photos and ignore the ppi setting.

[jackstraw]

thanks guys, for getting back to me so quickly with your answers. I really appreciate your help.

As you point out, an output program is able to change ppi resolution, so changing it isn't the problem. But here's where I think the problem is, and maybe I'm just worrying over nothing, but here's an example:

I shoot a 3072 x 2304 image (the highest quality on my camera). By default, its resolution is 180 ppi. This means that, without resampling, the largest I can print this image will be 12.8" x 17.06".

Now, from all I read, images should be 300 ppi when sent to a commercial printer. I'm not talking about fine art, or museum quality prints, just standard commercial printing.

So the problem is the limitations that 180 ppi puts on output size. How do I get a (let's say) 18" x 24" print from a 3072 x 2304 image?

The camera has 7.1MP, which I think is on the high side of p/s cameras, right? Would more megapixels solve the size issue? Or does it all come down to resampling the image in Photoshop?

If so, then do you just resign yourself to the fact that you're going to lose some quality when you upsample?

Thanks again for any thoughts you can share. I know this is a fairly complicated subject (at leat for me) - hope I'm not straining your brain cells too much!

[cwphoto]

thanks guys, for getting back to me so quickly with your answers. I really appreciate your help.

As you point out, an output program is able to change ppi resolution, so changing it isn't the problem. But here's where I think the problem is, and maybe I'm just worrying over nothing, but here's an example:

I shoot a 3072 x 2304 image (the highest quality on my camera). By default, its resolution is 180 ppi. This means that, without resampling, the largest I can print this image will be 12.8" x 17.06".

Now, from all I read, images should be 300 ppi when sent to a commercial printer. I'm not talking about fine art, or museum quality prints, just standard commercial printing.

So the problem is the limitations that 180 ppi puts on output size. How do I get a (let's say) 18" x 24" print from a 3072 x 2304 image?

The camera has 7.1MP, which I think is on the high side of p/s cameras, right? Would more megapixels solve the size issue? Or does it all come down to resampling the image in Photoshop?

If so, then do you just resign yourself to the fact that you're going to lose some quality when you upsample?

Thanks again for any thoughts you can share. I know this is a fairly complicated subject (at leat for me) - hope I'm not straining your brain cells too much!

Interpolation/upsampling - it's no big deal.

[jackstraw]

"Interpolation/upsampling - it's no big deal."

meaning you don't notice the compromise in quality? Or that there isn't any?

when you want to make an image bigger, do you change the pixel dimensions, and just let the resolution fall where it may? or do you change the resolution to something specific, and THEN change the pixel dimensions?

(I'm not looking for a Photoshop tutorial here, even though it may sound that way. I understand HOW to do it in PS. What I'm hoping for is some real world experience in enlarging digital images - specifically how "resolution for CMYK printing" figures into the process - and learn how you do it, what programs you use, etc.)

The reason I'm diving into this whole issue is because my work is more and more geared toward outputting to a commercial printer, and I've never had to supply CMYK separations in the past.

Maybe not too many folks use commercial printers for their work?

I realize if you're outputting to a deskjet, or even a laser printer, resolution is a non-issue; they'll both give you good results with resolutions of 150 ppi, sometimes even less, depending upon the image.

Do you ever send files as CMYK separations to a printer?

Thanks for bearing with me here...

[coldrain]

Just ignore the ppi value. You can print the picture as small and as big as you want, without ever thinking about pixels per inch. You do not even have to upsample a photo to print it very big, the software will just print the photo pixels very big. The 300 you refer to comes originally from DOTS per inch, DPI.
That was referring to the dots a printer sets. And a PIXEL from your photo when printed consists of mnay many dots from the printer.

So again... just totally forget about ppi, you do not need and and do not need to understand it.

[cdifoto]

"Interpolation/upsampling - it's no big deal."

meaning you don't notice the compromise in quality? Or that there isn't any?

when you want to make an image bigger, do you change the pixel dimensions, and just let the resolution fall where it may? or do you change the resolution to something specific, and THEN change the pixel dimensions?

(I'm not looking for a Photoshop tutorial here, even though it may sound that way. I understand HOW to do it in PS. What I'm hoping for is some real world experience in enlarging digital images - specifically how "resolution for CMYK printing" figures into the process - and learn how you do it, what programs you use, etc.)

The reason I'm diving into this whole issue is because my work is more and more geared toward outputting to a commercial printer, and I've never had to supply CMYK separations in the past.

Maybe not too many folks use commercial printers for their work?

I realize if you're outputting to a deskjet, or even a laser printer, resolution is a non-issue; they'll both give you good results with resolutions of 150 ppi, sometimes even less, depending upon the image.

Do you ever send files as CMYK separations to a printer?

Thanks for bearing with me here...

How's this for real world experience:

I printed and sold 20x30 inch poster size prints to clients using my Rebel XT and they were thrilled with the results. And I didn't charge just a few dollars over cost either. ;)

[Ray Schnoor]

Does your printer request that you send files at 300 ppi at the size you are printing, or is this something that you have just been told? All of the commercial printers that I have tried (Shutterfly, Ofoto, etc...) will print the photo you send them at the size you request. They will also tell you whether or not they recommend printing that photo(resolution) at the size you request. They will also recommend sizes where the resolution falls well below the 300 ppi you say. Prints I have received back from these companies have always been very good quality.

As to upsampling/interpolation, I have never seen a "noticeable" change in quality from a file resampled to 300 ppi from the original file if printing at a large size. Therefore, I now just print the original file without any resampling.

As I said before, most commercial printers will tell you whether or not the file you want to print is suitable for printing at the size you are requesting. All of the printers I have used have also given excellent results at ppi as low as ~150.

Ray.

Ray.

[cwphoto]

"Interpolation/upsampling - it's no big deal."

meaning you don't notice the compromise in quality? Or that there isn't any?


Well there is always a compromise in quality, but it's unavoidable and needs to be considered within context.

If you choose a particular resolution (ppi) that you need then there is always a finite size to the print. Eg; if I use 300ppi on my camera it gives an image size of just under 8x12".

To go bigger you can just drop the ppi or use interpolation (I think) to give you the right image size you want.

Remember that a larger image is supposed to be viewed at a proprtionally greater distance nullifying the effects of a drop in ppi. Obviously one also needs to take into account any cropping.

[jackstraw]

Excellent! Thank you guys - I'm glad I found this forum; I've learned all I need to know right now.

Between the advice to "just ignore ppi" and "your printer will tell you if your image will suffer" is the answer I need. I got the "you must have 300ppi for commercial work" from a digial imagemaking tutorial, and from reading some books on digital image editing.

Interesting, the consensus here seems to be: forget resampling, quality is perfectly acceptable at levels as low as 150. I think I've listened a little too closely to the "experts" who write the books.

I highly recommend these books and the movie tutorial also, especially if you already know as much as you guys do. As a true beginner in digital imagemaking, I had nothing to compare to. You'll prob get more out of them than I did, since you already have a base of experience to draw on.

Books: Katrin Eismann's "Restoration and Retouching" and "Masking and Compositing"; Blatner/Fraser's "Real World Photoshop CS2"

Movie Tutorial: Taz Tally's "Introduction to Digital Photography" (lynda.com)

Thanks very much for the help folks. I really appreciate you taking the time to share your thoughts.