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Canon file dimensions.
Henry Hsu, Student/Intern, Photographer
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Los Angeles | CA | USA | Posted: 10:10 PM on 11.02.05 |
->> Hi.
I use Nikon cameras, but when I help the paper edit photos I get Canon files that seems a bit strange to me.
The resolutions are at 72px/inch, where as my nikon ones are 300px/inch or 200px/inch.
I have to reduce the file size down to 10 inches at its longest or widest for placement, that way they won't have to struggle to shrink things down.
So if I take a canon file of 48.667 inch wide and 32.444 high at 72 px/inch and make it 10 inch at its widest, I only get 720 pixels. Does this not degrade the quality of the image? Especially for print?
Sorry if this is a bit confusing. |
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David Wanner, Photographer
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North Ridgeville | OH | USA | Posted: 10:23 PM on 11.02.05 |
->> Henry,
I process for 7 different stringers at or papers, some use Nikon, others Canon as I do, and I think others use camera phones but that's for another thread.
If proportions are constrained, adjust resolution first-we use 200, then adjust to the width that you need. If you adjust to width first it does what you describe.
I hope this helps, if I'm wrong hopefully you'll get one of the PS gurus to chime in. We're still using PS 5.5. |
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Henry Hsu, Student/Intern, Photographer
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Los Angeles | CA | USA | Posted: 10:37 PM on 11.02.05 |
| ->> Doesn't increasing the resolution from 72 to 200 soften the image a bit? Or is it just with really low quality photos? |
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Mark Buffalo, Photographer
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Lonoke | AR | USA | Posted: 10:43 PM on 11.02.05 |
->> Henry
It is all about keeping the file in proportion.
For example, my Canon 10D with the software loaded on my computer, files come in at 12x18 at 180...which is the equivalent to 20x30 at 72 or somewhere in that vicinity. It's all about the pixel numbers such as 2100x3200 pixels, which is what gives you your camera's resolution.
With what you are saying, the file size is just keeping its proportion.
Mark |
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Vern Verna, Photographer
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Greenville | SC | United States | Posted: 10:59 PM on 11.02.05 |
| ->> i can make my Canon file 48.667 at 72 dpi or 11.68 @ 300 dpi by changing preferences. either way it is the same size file. If you size the image down to 10 inches at 72 dpi and then try to take that smaller file at 72 dpi and make it 200 then it does look like crap. But if you take the 48 inch file at 72 dpi and size it to 10 at 300 without sizing it down first then you get a nice usuable file. You actually throw info away to size it to 10" at 300dpi cause a canon mark ii image off the camera is 11.68in @ 300dpi. if you take a 72 dpi photo at 10" and blow it up to 10" at 200dpi then you blow each pixel up about 3 times and while you are not softening it you are pixelating it. It is all about how you have the constrain proportions set in the ps image size box. |
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Henry Hsu, Student/Intern, Photographer
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Los Angeles | CA | USA | Posted: 11:04 PM on 11.02.05 |
| ->> I understand now. I had a false impression that increasing px/inch makes the images degrade. Thanks alot for your help, David and Mark. |
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Greg Ferguson, Photographer
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Scottsdale | Az | USA | Posted: 2:02 AM on 11.03.05 |
->> This is one of those smoke and mirrors things that comes up periodically.
The numbers you're seeing are really just the software's way of trying to be helpful - it's trying to present the dimensions of the image to you based on some given DPI.
That DPI could be set to 72 or 240 or 1024 or 3000. The number is only important as a way of helping you understand how large the image will appear when presented on a device using that DPI. A 72dpi monitor would have a huge image. A super high resolution printer, say something like a slide printer, would have a tiny image given the same number of horizontal and vertical pixels.
You can fiddle around in Photoshop to see how it'll change the representation without it actually changing any pixels by opening the "Image/Image Size..." dialog, clearing the "Resample Image" checkbox, then start entering different values for "Resolution". Photoshop won't do anything to resize the image or fiddle with pixels as long as the "Resample Image" checkbox is cleared. For example, a 2400x1920 pixel image is an 8"x10" at 240 dpi. At 72 dpi it's over 33"x26" though the pixels haven't changed. A device that needs 1024 dpi would output a 1.8"x2.3".
An initial DPI value can be embedded in an image file to tell Photoshop (or other apps) what to use for the subsequent DPI dimension calculations. Photo Mechanic can set it during ingest so those bogus/default 72dpi values will be more useful from the start of the workflow. |
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Henry Hsu, Student/Intern, Photographer
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Los Angeles | CA | USA | Posted: 3:33 AM on 11.03.05 |
->> So, lets say an image is created at 72dpi gets increased to 300dpi and then printed with a large format printer, will the image be as sharp as when it is viewed on the monitor?
(Sorry, I'm slowly understanding this more) |
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Greg Ferguson, Photographer
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Scottsdale | Az | USA | Posted: 4:30 AM on 11.03.05 |
->> It doesn't matter what DPI it was created at or how much the DPI setting is increased or decreased. If the "Resample Image" checkbox is cleared the image will not be modified.
If the image is created at 72DPI and has 2400 pixels horizontally and 3000 pixels across, it will display as a 33.3"x41.6" image (if you could find a monitor that big).
Without making any changes, you could print the same image to a 300DPI printer, and it would come out as an 8"x10" print. It would appear sharper than how it appeared on the 72dpi monitor because the monitor is a low-resolution device, especially when displaying images at 100%. Tell the monitor to display at 50%, and the image would take up 16.5"x20.5" and appear sharper (one of the reasons we don't try to inspect digital images at 100%).
Say you created a new image using 72DPI and relied on the 8"x10" dimensions displayed in the "New" image dialog, you'd only have 576x720 pixels, which would output as 1.92"x2.4" on the printer. If you told Photoshop to resize the image, it'd have to make up the difference between those 576x720 and 2400x3000... and "make up" is a key phrase, because it'd be creating a huge number of very bogus color and tone filler pixels that would result in an image that was horribly blurry and pixelated. That sort of scaling would result in miserable results. On the other hand, if you'd started with a setting of 300dpi, that same 8"x10" image would have a very usable image size.
Set your DPI setting to what your output device wants and all your displays and readouts in Photoshop will reflect either the actual pixel dimensions, or the measurements relative to that 300 DPI. Once you've set it to 300 (or whatever you output at) leave it alone and only revisit that particular setting when you need to fix te displaying of the dimensions for an image missing the correct setting or to get an idea what the image size will be when output to a different resolution device. |
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Henry Hsu, Student/Intern, Photographer
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Los Angeles | CA | USA | Posted: 5:16 AM on 11.03.05 |
| ->> Thanks alot, Greg, for this detailed explaination! |
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