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03-21-2011, 07:19 PM   #1
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Image Resolution Issue - Can't shoot at 300 DPI

I have the settings at 12MP, and 3 stars for JPEG quality (highest), but all my images still come out at 72 DPI. I've tried switching to RAW, but same thing happens.

All my pics are coming out at 72 DPI, regardless of the setting I change, and the image size never goes above 4MB. How do I change the settings so my pics are taken at 300 DPI and not at 72 DPI?

03-21-2011, 07:23 PM   #2
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Which camera?????
03-21-2011, 07:30 PM   #3
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Are you using Aperture?
03-21-2011, 07:30 PM   #4
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Pentax K-X

03-21-2011, 07:46 PM - 1 Like   #5
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Here some answer
Why are my images only 72 dpi?
03-21-2011, 07:50 PM - 2 Likes   #6
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The actual DPI of the picture depends on the image size in pixels divided by the image size in inches that you are viewing it or printing it at.
I'm willing to bet that value of 72 DPI is just written to the EXIF at some stage and really doesn't mean anything. You set your image editor to write a different value, eg. Adobe Lightroom.
I set my Lightroom to output images with "300 dpi", but the reality is that value of 300 is only written to the EXIF properties. As I said, the actual DPI is completely related to the resultant size of the image and how many pixels you started with.

So... don't worry about it If you change that setting in the file properties your images will look exactly the same. You're not losing any quality.

EDIT: to be more correct, "PPI" indicates pixels per inch, which is more relevant when you are talking about images displayed electronically. DPI is of course dots per inch, which indicates that the image is printed.

The value of 72 DPI in the file will not mean that your image will be printed at 72 DPI. It will be printed at whatever the pixels/print size in inches works out to be.

Last edited by goddo31; 03-21-2011 at 08:48 PM.
03-21-2011, 07:55 PM   #7
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Hi Andy,

Nothing's wrong. The 72 DPI is, I believe just the screen resolution for display. It has nothing to do with actual resolution of the image. To see this look at the pixel dimensions. I seem to remember that 72 DPI was a standard for computer screen display, and it really has nothing to do with anything AFAIK.

My K-10 shooting 10 MP *** jpegs usually created files that seem to average around 3 MP for an image with a decent amount of content, so 4 MP doesn't sound out of bounds for a 12 MP at the same compression. I currently get 6-7 MP with my 16 MP K-5 at jpeg ***.

If the images look ok and the pixel dimensions are 4288 x 2848, everything's normal.

Scott
03-21-2011, 08:25 PM   #8
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As others have essentially said, "DPI" is a meaningless term when it comes to digital photography. The term you're looking for is "PPI" (pixels per inch), which only applies when printing. A digital image has a set number of pixels, but you can set the PPI to whatever you want during the printing process. A higher PPI will result in a smaller print, and vice versa.

03-21-2011, 08:50 PM   #9
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I hope that 72 DPI is just a setting, but it doesn't seem to match up with the rest of my settings...but I get the DPI vs PPI, so thank you.

When I look at the info of my photos, it says DPI height and width of 72 DPI, but the image size is 4288 x 2848 pixels, and it's only 3.4MB.

Given I have the camera set at the highest resolution, and the camera can take 12.4MP photos, shouldn't the file sizes also be larger than 3.4MB?

I'm new at this, so bear with me, but it's just not making sense to me why the camera would be resorting to a default of 72 DPI, if it's not actually taking photos at that resolution.
03-21-2011, 08:53 PM   #10
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DPI is a print setting- change it in photoshop if you'd like it higher.

Adam
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03-21-2011, 09:08 PM   #11
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Here's a formula

pixels/DPI (PPI is the same thing, for our purposes) = print size.

You can't change from 72DPI at the time of taking the picture, that is the number that is embedded in the file, you can, however, change it to whatever you like in post processing.
Note that the above formula or a variation of it, will always apply.
03-21-2011, 11:19 PM   #12
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QuoteOriginally posted by Andy6140 Quote
When I look at the info of my photos, it says DPI height and width of 72 DPI, but the image size is 4288 x 2848 pixels, and it's only 3.4MB.

Given I have the camera set at the highest resolution, and the camera can take 12.4MP photos, shouldn't the file sizes also be larger than 3.4MB?
First of all, compression makes files smaller. Next DPI has to do with printing. A program like Irfanview allows you to print based on DPI (amongst other settings); the size of the print with 72 DPI will be 4288/72 = 59.5 inch.

QuoteOriginally posted by Andy6140 Quote
I'm new at this, so bear with me, but it's just not making sense to me why the camera would be resorting to a default of 72 DPI, if it's not actually taking photos at that resolution.
It's just a number that is not used by the camera. Some cameras put 300DPI in the EXIF, others 72DPI. It's the print resolution, not the camera/sensor resolution that DPI refers to.
Your sensor is approx. 24mm wide, so rounded this is approx. 1". The sensor resolution is 4288 approx. pixels per inch.

And to add to the confusion: I'm viewing this on a monitor that is approx 17" wide. The monitor has a native resolution of 1680x1050. So the screen resolution is about 100 pixels per inch (1680/17).
03-21-2011, 11:19 PM   #13
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QuoteOriginally posted by Andy6140 Quote
<snip>
When I look at the info of my photos, it says DPI height and width of 72 DPI, but the image size is 4288 x 2848 pixels, and it's only 3.4MB.

Given I have the camera set at the highest resolution, and the camera can take 12.4MP photos, shouldn't the file sizes also be larger than 3.4MB?
<snip>
The DPI is nothing at all to do with the size of the file in MB. As others have said it's just a value in the EXIF and means nothing until you start doing something with the images that takes notice of it - printing them, putting them into word for example. Web browsers ignore it.

4288 x 2848 = 11 MB (approx) but the JPG image is compressed.
03-21-2011, 11:31 PM - 1 Like   #14
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QuoteOriginally posted by Andy6140 Quote
When I look at the info of my photos, it says DPI height and width of 72 DPI, but the image size is 4288 x 2848 pixels, and it's only 3.4MB.

Given I have the camera set at the highest resolution, and the camera can take 12.4MP photos, shouldn't the file sizes also be larger than 3.4MB?

I'm new at this, so bear with me, but it's just not making sense to me why the camera would be resorting to a default of 72 DPI, if it's not actually taking photos at that resolution.
Hi Andy,

The reason the file size is 3.4 MB is that you are shooting Jpegs. Jpeg is a digital image format that compresses the digital image file automatically when it's saved, and expands it automatically when it's opened. It's the most universally recognized digital image format for computers and their programs. I really can't describe the process here. Google it if you're curious.

Pentax DSLR shooters also have the option of shooting either PEF or DNG RAW. RAW is a generic term for the camera maker's interpretation of the raw data that is collected by the sensor. PEF is Pentax's proprietary format, and although it's named the same across models, it's different for each model of body, and DNG is an open source format developed by Adobe, the software mfg. PEF is a losslessly compressed RAW, and DNG is not compressed, so will create larger files. I also won't go into the explaining RAW.

Either of these RAW formats will give you larger files (in fact larger than the 12 MB you might expect), and some benefits and disadvantages. RAW is not an image format, so won't be recognized by computers without the proper codec installed. Some image viewers won't be able to recognize them unless a plugin is installed. There has been an ongoing controversy as to whether it's better to shoot RAW or Jpeg, and there really is no answer, except that either can be best in some circumstances -- there's already a current thread, and many more historically discussing this, and I don't think you want to start another one here.

The bottom line is go ahead and continue to shoot jpegs. If you want more flexibillity in Post Processing, look into RAW, and what you'll need to do this. I don't want to sound condescending, but if you don't know what it is, and are new to your camera, it's probably best to learn the camera first, then decide if you want to delve into RAW once you've got a good handle on the camera.

Scott
03-22-2011, 01:12 AM   #15
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QuoteOriginally posted by Andy6140 Quote
I'm new at this, so bear with me, but it's just not making sense to me why the camera would be resorting to a default of 72 DPI, if it's not actually taking photos at that resolution.
The DPI setting really means nothing in my opinion. And DPI in general really means nothing until you are going to print...

Here's an example with the formula that some of the guys have provided.

If your image size (pixels) are 4288 x 2848.
And you want to print at 8x12.

DPI(K-x on 8x12)
= pixels length / print length in inches = 4288 / 12 = 357DPI
= pixels wide / print width in inches = 2848 / 8 = 356DPI

(BTW, If both dimensions are not the same then you probably need to crop the image to a different aspect ratio.)

And then if you want to print at 16x24:

DPI (K-x on 16x24)
= pixels length / print length in inches = 4288 / 24 = 178DPI
= pixels wide / print width in inches = 2848 / 16 = 178DPI

----
In regards to displaying your image on a computer, I think the value in PPI will change depending on what size the image is resampled to. Meaning, the image will be 4288x2848 but it will be resampled to resemble whatever size you view it at and the PPI will change. In theory, of course the monitor will only have a limited resolution too. Permanently resizing the image will be different, I'm pretty sure..
Even so, I don't see how it matters. What does matter in terms of resolution is how many pixels you have but most importantly how sharp the photo is. You might be able to improve your "resultant IQ" by better technique/tripod and sometimes by a different lens.

Good luck, and try not to worry about DPI too much
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