changing DPI

[Jolne]

Chaning DPI
Ok, Here is my problem. I have a Canon 10D.
When I take a picture with the highest quality it sets it at this:

Pixel Dimensions:
Width: 2048 pixels
Heigth: 3072 Pixels

Document Size:
Width: 11.378 Inches
Height: 17.067 inches
Resolution: 180 pixels/inch
My question is: Do I need to change the pixels on the Resolution to get a better quality picture? And if so, how do I do this without wrecking it? I want to be able to print large sizes...over 11x14. Like 16x20. Can anyone help me?
Thanks Alot!

[etaf]

the pixels are the important thing here - if that the biggest on the camera than thats the quality.
Now printing - you probably have a default of 180 PPI so thats why it states that - now to print for top quality prints around 300 PPI is the setting
However, somepeople say you can set to as low as 150 - I use 300 and i think epson printers like 240

does that help

to get bigger prints you will need to enlarge - there are some photoshop techniques to do this and a lot of people seem to think to resize by 10% is OK - otherwise use something like genuine fractuals program

[wolf]

Changing the DPI will not make a difference in the picture quality. You can up size your 2048 x 3072 image with software such as Genuine Fractals to produce a larger print of good quality.

Edit: I type to slow. http://photography-on-the.net/forum/images/icons/icon7.gif

[PacAce]

As long as you are shooting your JPG using Large/Fine, you will have the highest resolution image possible with the 10D (short of shooting in RAW). Don't mind the 180 pixels/inch resolution. If you've read any of the other DPI or resolution related threads here, you'll find that the resolution stored with the image is practically meaningless.

Actually, you should count your blessings because those with the newer cameras have their JPG image file resolution set to 72 ppi and that really has some people in an uproar. :mrgreen:

[tim]

http://photography-on-the.net/forum/showthread.php?t=83445

[Debian Dog]

Yep same with video!
http://www.scantips.com/no72dpi.html

[SkipD]

Yep same with video!Please don't confuse that article with video images (motion pictures). It is merely talking about computer video displays.

The thing that folks need to understand is that the resolution (PPI/DPI) number only relates to PRINTING. It is pretty simple. However, so many uninformed people look at specifications and get upset without understanding them.

[Debian Dog]

It is exactly the same. DPI and video have NOTHING to do with each other. I am in no way "confused". ;)

If you would like to read more about it, I run the iMovie FAQ and you can read more about scanning pictures and using it in video here (http://danslagle.com/mac/iMovie/video/2003.shtml) and also here (http://danslagle.com/mac/iMovie/video/2002.shtml)

numbers only relate to PRINTING Exactly.

[Jolne]

I am not interested in what it looks like on screen. I am only interested in printing.
So if I want to print a picture say like a 16x20 size (hanging on my wall)...do I need to change that 180 to a higher resolution?? Or leave it? Is it better to shoot in raw?

[etaf]

for top quality usually a rule of thumb is cahnge to 300 ish i heard some epson printers like 240
but if you want a 16x20 on the wall then you need the pixels to start with
so to get 16" at 300PPI pixels per inch - then 16 x 300 = 4800 pixels
20 " at 300PPI 20x300 = 6000
so you need an image 6000x4800 pixels to start with
its better to shot in raw as that is like a negative and does not have any camera software applied - so you can do anything you like after the shot

what the max size pixels you can get out of your camera

theres loads of posts here about printing out and resolutions - but as a new member I can point you there

[Jolne]

OK, so if I shoot in raw..then it does not matter if I change the resolution...but if it is already set, it will not be good right?
Also...if I change the 180 to 300...won't that affect my image quality? I just do not get this...grrrrr

[pcasciola]

Set it to any number you like. It's doesn't affect image quality at all. If you tell your software or lab to print at any given size, the number is meaningless.

[Jolne]

Will a print size 16x20 or larger be poor quality if I keep the settings just as they are? (Look at 1st post for what is set)

[etaf]

No
The PPI just tells the printer how many pixels per inch it will need to print out at
so if you have an image 100x100 pixels taken in raw or jpg off the camera
the size is 100 x 100
if in the image editor it defaults to say 10PPI that means nothing just a default setting and if you use it TO PRINT ONLY then it will use 10 of your pixels for every inch therefor the you will be able to print out 10" x 10" BUT image how the image print will lookk with only 10ppixels perinch - pretty rubbish very blocky
now you can change that setting to 100PPI
nothing will happen to the image on the screen or nothing has happened to the image quality but WHEN YOU PRINT IT the printer will know to use 100 of your pixels for each inch - so it will print 1" x 1" and you will get a better quality print.....

so the rule of thump is that for top quality PRINTS you need to use 300 PPI
now on our example this will print out at a size of 100pixels /300PPI = 1/3" x 1/3" very small
so the more pixels you have in the original image the better the PRINT quality will be possible

does that help

[Jolne]

OK yes that helps..but....how do I change it to do that when I take the pic? The 10D I have sets it at that automaticly...so Can I change it before I take the picture? IF not...will shooting in raw help?

[etaf]

Ok try again with your example
Pixel Dimensions:
Width: 2048 pixels
Heigth: 3072 Pixels

Thats all that matters - thats the quality on screen and stored.
Now you want to print the image
SO as a rule of thumb you will need to have 300 pixels for every inch of paper
so you have 3072 pixles and have to divid that by 300 to see how many inchs you can print
3072/300 = 10.24"
2048/300 = 6.8"

so thats the biggest print you will get at high quality printing.
NOW some people say you dont need as much as 300 PPI to get a good quality print and these varies from person to person - some epson printers will provide a good quality print at 240PPI so with less of YOUR pixles per inch you can get away printing larger

can you print 20x16
so you have 3072 and want a size of 20"
Pixels / PPI = inches
so Pixels/iches = PPI
3072/20 = 153PPI
can you get a good quality print with only 153 pixels for each inch - i dont think so - but other may disagree and lots of threads here - final test print it out and see

i'll wait for your response before answering the question re 10D raw and setting - if you still dont understand as we are crossing

[Jolne]

Ok . I understand that now. Thank you for making it easier for me to get. You are very patient. Now...shooting in raw...does that just mean I can set things however I want? And the pixels to whatever I want? Should I just shoot in raw and it will fix the problem?

[SkipD]

I am not interested in what it looks like on screen. I am only interested in printing. So if I want to print a picture say like a 16x20 size (hanging on my wall)...do I need to change that 180 to a higher resolution?? Or leave it? Is it better to shoot in raw?Jolne, what you need to know is fairly simple. Break the process down into steps....

First - what are the horizontal and vertical pixel count numbers of your image? For your camera, those numbers are 3072 and 2048 pixels.

Second - how large do you want to print? Let's use your example of 16x20 inches. First, the 16x20 format is not the same aspect ratio (width-to-height or height-to-width, how ever you want to consider it) as the camera's image. The camera's image has a 2:3 height-to-width ratio (assuming the height is the short distance, like your computer monitor). Thus, you will have to crop at least the long distance (width if in landscape mode like the computer monitor). Let's assume that works for you. The pixel count of the resulting photo image would be approximately 2560x2048 pixels.

Third - take the larger pixel count number (the 2560) and divide it by the inches across the long dimension of the print (20 inches). You will have 128 pixels per inch making up your print. Do the same math for the other dimension (2048 pixels vs 16 inches), and you get exactly the same pixels-per-inch value.

Fourth - you have to determine if the resolution of the resulting print will be acceptable to you. 128 pixels per inch is a little coarse for a lot of folks who might examine the print up close. Viewed from a couple of feet away, it might be quite acceptable. I think you will find that most printing is done at a minimum of 240 PPI, and some folks (like me) usually print at least at 300 PPI for maximum resolution of the print.

The actual "setting" of the PPI count is a process done when you tell your photo software what size to print to. This is the ONLY time that PPI means a thing to you. I hope the four-step thinking process above makes this thing with PPI count a little more understandable.

There is software available that will let you increase the image's pixel count so that you can make larger high-resolution prints. It isn't cheap, however. The latest version of Genuine Fractals - designed to run with Photoshop CS2 - has to run on an XP platform (for the PC) and costs about $200. You should also have LOTS of RAM memory in the computer to use that sort of software, adding to the costs.

[cecilc]

Pixel Dimensions:
Width: 2048 pixels
Heigth: 3072 Pixels

This is nothing more than a math problem, folks ....

You already know just how many pixels you've got in your image file (above). And you're trying to find out how many pixels per inch will be in a 16x20 image from that image size.

2048 divided by 16 = 128 pixels per inch
3072 divided by 20 = 153 pixels per inch

So, if you set the DPI setting to 153, you'll get an image that prints at 20x13.25 (approximately). Most labs that I deal with insist that the image be 300 pixels per inch to print the best quality print.

Now, if you need to "enlarge" that print to 300 DPI AND print at 16x20, you'll have to "interpolate" that image "up" to handle the 300 DPI so that your image is 4800 pixels by 6000 pixels (300x16 and 300x20). You can do that in PS or you can invest in Genuine Fractals or you can just have the printer driver do that for you in the print process.

It's all in the math - multiplication and division .....

[cecilc]

Should I just shoot in raw and it will fix the problem?

No ....

As I said, you're dealing with a math problem, not a shooting problem ....

RAW will enable you to change a lot of variables in your image, but it won't create pixels for you ....

[SkipD]

Ok . I understand that now. Thank you for making it easier for me to get. You are very patient. Now...shooting in raw...does that just mean I can set things however I want? And the pixels to whatever I want? Should I just shoot in raw and it will fix the problem?ETAF and I were typing at the same time, it seems.....

RAW mode has no settings for the PPI value. Again, it makes absolutely no difference what number is chosen by Canon for the camera's image data. It's only when printing that you would even care about the PPI value, and it's when you spread the pixels in the image file across paper that it is determined.

RAW images allow you to have MUCH more control over the image than shooting in JPG mode, for example. When converting RAW images to other file types (which must be done - you don't work directly in RAW), you can choose the color balance that you need - you may have chosen the wrong color balance setting in the camera, for example. You can also make other changes when converting from RAW, but for most people the main advantage is the simple color balance conversion.

[etaf]

Ok . I understand that now. Thank you for making it easier for me to get. You are very patient. Now...shooting in raw...does that just mean I can set things however I want? And the pixels to whatever I want? Should I just shoot in raw and it will fix the problem?
RAW is like a negative it has not been touched by the camera software and will be how the sensor saw the image so you will get maximum size pixels and then you can make adjustments to the image like sharpening and colourspace - which the camera may set for you otherwise.
so you get more choice to change the image after the shot.
some people always shoot in RAW myself included and others prefer to shot in jpg - theres a lot of post on raw and jpg so have a search for RAW

skipD :) and again

[Jolne]

Well I will work on it. Thanks for your help everyone. I just am worried that the photos I have taken, that need to get blown up, will look like crap.

[twalker294]

Well I will work on it. Thanks for your help everyone. I just am worried that the photos I have taken, that need to get blown up, will look like crap.

No they won't. I have printed many 16x20 canvases from my 10D and they are beautiful. I resample to 200 dpi before sending the TIFF to the printer because the nature of canvas prints makes them a bit more forgiving of resolution so 200 is just fine. Actually even for traditional prints at that size 200 dpi would probably be fine unless you got right up next to the picture and then you would see a bit of fuzziness. But keep in mind the larger the print, the farther away it is intended to be viewed from. You can easily do 20x24 with a 20D and it will look great.

[etaf]

yep maybe, but thats because of the max pixels you have and thats why people spend extra money and instead of getting a 2MB camera get a 6MB camera because it has more pixels and prints larger as a result of more pixels.
but if you have used the maximum pixels available from your camera than that the biggest print you will get - now getting to 20x16" may need some manipulation in photoshop or GF - but until you print it you wont know if its acceptable to you.

what size printer A4/A3 and make model do you have

SEE
twalker294
as I said different people have different views on what is acceptable and possible with PPI thats why its so difficult - I know someone who prints 20" off a 4MB camera - I think the prints look blotchy He loves them ......
give it a go.

hence printer question

[AJSJones]

Jolne, Have you ever had (or seen) film developed and prints made? You may well have asked for "4x6" - putting that label on doesn't mean it can only be printed at 4x6. It doesn't do anything to the negatives. It's just an instruction to the printer. You can take the same negatives later and say "16x24 please". Still the negatives don't change. If you want 16x20, you'll have to tell the printer which part of the negative not to print...

Same way, putting a "label" (or "tag") on the file in software saying "72ppi" or "300ppi" doesn't change anything about the pixels in the file, it's just an instruction that some printers need and you can change that at any time.
What you change it to will depend on how big you want to print. Then it becomes an arithmetic problem and a choice of how far away you want them to be viewed. If you print them too big, and look at them too closely, of course they'll look like cr*p. Same was true of film :D

Andy