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02-20-2015, 04:31 PM   #1
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Resolution question RAW vs. jpg

When I take pictures in jpeg on the K30, the resolution is 300
When I take pictures in RAX with the K30, the resolution is 300
When I take ANY pictures with the K30, the resolution is 300
The size of the file is larger in RAW and there is a difference in the way the photo looks, especially with colors.
A teacher recently told me that this cannot be, the resolution in jpeg should be 72, not 300.
So, my question is this:
Is my camera malfunctioning or is the teacher wrong, because all of my pictures end up with resolution of 300.

02-20-2015, 04:39 PM - 1 Like   #2
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The dpi resolution is a print setting. Your camera's resolution is measured in pixels. It should be 4928 x 3264 for both JPEG and RAW.

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02-20-2015, 04:55 PM - 1 Like   #3
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I think the teacher is wrong. That has nothing to do with it. A 4936 x 3264 pixel image at 300 ppi is 16.4 x 10.9 inches (rounded), at 72 ppi it is 68.4 x 45.3 inches. Pppi on screen or dpi printed. jpg or raw formats have nothing to do with it. I may not have explained this well, but I would think there are some pretty good explanations on the web.
02-20-2015, 06:11 PM   #4
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QuoteOriginally posted by NancyK Quote
A teacher recently told me that this cannot be, the resolution in jpeg should be 72, not 300.
Either you misunderstood what the teacher was saying or they have no idea what they are talking about are confused.

An image is measured in pixels, however the resolution in dpi or ppi determines the actual size in physical inches. As noted above the same image @ 72 dpi will print far larger than if it was printed at 300 dpi, but the image remains the same. Screen images are usually exported at 72dpi as that is all the resolution needed for most screens. High quality printers will need to be fed at 240 to 300 dpi in order to produce a good looking print depending on the media. Canvas prints for example are often done 150 to 180 dpi because the canvas texture allows lower resolution images to still look fine.

Get used to thinking in pixels x pixels for image files, dpi or ppi are only relevant when associated with a particular output device or finished product.

02-20-2015, 06:35 PM   #5
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Yep, the computer video display system does not use dpi, it uses pixels.
For a more thorough explanation see ;
Say No to 72 dpi
and
The Myth of DPI | Webdesigner Depot
02-20-2015, 07:04 PM   #6
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QuoteOriginally posted by NancyK Quote
When I take pictures in jpeg on the K30, the resolution is 300
When I take pictures in RAX with the K30, the resolution is 300
When I take ANY pictures with the K30, the resolution is 300
The size of the file is larger in RAW and there is a difference in the way the photo looks, especially with colors.
A teacher recently told me that this cannot be, the resolution in jpeg should be 72, not 300.
So, my question is this:
Is my camera malfunctioning or is the teacher wrong, because all of my pictures end up with resolution of 300.
As others have already said, your teacher is wrong.

Raw files are larger than JPG because JPG compresses the data, losing some details in the process. The camera also boosts colors, sharpness, and some other elements of the file before saving JPG; that's why JPG colors look more vibrant than raw. Raw is considering a starting point that holds all the data captured by your camera but then you need to develop the raw using Pentax's software, or Lightroom, Photoshop, etc. Raw is more work for you but allows more latitude for you to finesse the final result. (there are many threads about raw vs jpg)

Last edited by DeadJohn; 02-20-2015 at 07:25 PM.
02-20-2015, 07:10 PM   #7
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QuoteOriginally posted by NancyK Quote
When I take pictures in jpeg on the K30, the resolution is 300
When I take pictures in RAX with the K30, the resolution is 300
When I take ANY pictures with the K30, the resolution is 300
The size of the file is larger in RAW and there is a difference in the way the photo looks, especially with colors.
A teacher recently told me that this cannot be, the resolution in jpeg should be 72, not 300.
So, my question is this:
Is my camera malfunctioning or is the teacher wrong, because all of my pictures end up with resolution of 300.
You can't view RAW files. What you see is a bitmap rendition of the RAW data which when in Lightroom is updated live as you tweak the development parameters.
02-20-2015, 08:37 PM   #8
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The JPEG is the same regardless of the dpi setting. It exists solely as instructions (hint actually) to the printer indicating intended final dimensions. The printer will up/down sample as is appropriate to make that dpi.


Steve

02-20-2015, 08:53 PM   #9
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Thank you all for your help....it sure can get confusing in a hurry!
02-20-2015, 09:18 PM   #10
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QuoteOriginally posted by stevebrot Quote
The JPEG is the same regardless of the dpi setting. It exists solely as instructions (hint actually) to the printer indicating intended final dimensions. The printer will up/down sample as is appropriate to make that dpi.


Steve
I suppose it would be good to expand a little. The confusion is mostly the fault of Adobe Photoshop. A generation of graphics professionals were trained to think of image size in terms of dpi. This is great for printing, where dpi is an indication of resolution and there is a direct proportional relationship between that and size, but for digital captures the total number of pixels is the best indicator of resolution.

More pixels = more data = higher resolution

There is a rather complete and (unfortunately) sarcastic discussion at the page linked below.

Dpi, misunderstandings and explanation, what is dpi

What does this mean in practice? It all depends on if and how you print. If you aren't printing, it makes no difference. If you are printing on your home computer, it probably still makes no difference, particularly if you are printing directly from Elements, Lightroom, Photoshop, Paintshop Pro, The Gimp or whatever. Those programs typically work directly with the printer driver to give you whatever dimensions you specify and will up/down sample the image as needed. With most modern cameras and consumer printers you will have enough pixels to print to up to the maximum paper size with reasonable quality.

Where it gets complicated is when you having larger prints done by a print shop or service bureau. The industry standard is 300 dpi on the paper meaning that if you want 9"x6" inch print from APS-C you will have to have 2700 pixels on the long side of the image. That would be about 5 Megapixels with a little cropped off to make it fit. 10"x8" requires 2400px on the short side and a cropped 7 Mpx APS-C image and so on.



Steve
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