Discussion
reposted from me last year,
"resolution is a very misunderstood subject indeed. To quote a pixel size (e.g. 600x400) in relation to a resolution (e.g. 72DPI) has absolutely no meaning when the image is being displayed on a computer screen. A 600x400 picture is EXACTLY the same whether it is 1 DPI or 1000 DPI - it is always 600x400 pixels.
This is not the same if you are quoting the picture size in physical dimensions, i.e. inches/centimetres/whatever. For example, a 6"x4" print at 10 DPI is made from a 60x40 pixels photo, whereas the same print at 300 DPI is made from an 1800x1200 pixel image. Obviously the higher DPI image is a better quality in this instance.
The difference is due to the fact that a pixel is not a set size, whereas an inch obviously is."
in other words, don't worry for a minute about what resolution your camera stores pictures at
"resolution is a very misunderstood subject indeed. To quote a pixel size (e.g. 600x400) in relation to a resolution (e.g. 72DPI) has absolutely no meaning when the image is being displayed on a computer screen. A 600x400 picture is EXACTLY the same whether it is 1 DPI or 1000 DPI - it is always 600x400 pixels.
This is not the same if you are quoting the picture size in physical dimensions, i.e. inches/centimetres/whatever. For example, a 6"x4" print at 10 DPI is made from a 60x40 pixels photo, whereas the same print at 300 DPI is made from an 1800x1200 pixel image. Obviously the higher DPI image is a better quality in this instance.
The difference is due to the fact that a pixel is not a set size, whereas an inch obviously is."
in other words, don't worry for a minute about what resolution your camera stores pictures at
dcw@pr said:
reposted from me last year,
"resolution is a very misunderstood subject indeed. To quote a pixel size (e.g. 600x400) in relation to a resolution (e.g. 72DPI) has absolutely no meaning when the image is being displayed on a computer screen. A 600x400 picture is EXACTLY the same whether it is 1 DPI or 1000 DPI - it is always 600x400 pixels.
This is not the same if you are quoting the picture size in physical dimensions, i.e. inches/centimetres/whatever. For example, a 6"x4" print at 10 DPI is made from a 60x40 pixels photo, whereas the same print at 300 DPI is made from an 1800x1200 pixel image. Obviously the higher DPI image is a better quality in this instance.
The difference is due to the fact that a pixel is not a set size, whereas an inch obviously is."
in other words, don't worry for a minute about what resolution your camera stores pictures at
...and to proove it
two pics (taken today) stored at 360 and 72 (from one raw)
72
360
Just don't ask why I was taking pics of an Audi
- hey... at least IT WAS CLEAN 
...I'll get me coat.
GetCarter said:Not quite true - this figure of 72dpi comes from the early ages of Macs with their A4 screens.
72 is the maximum that monitors reproduce. As Simpo says, it's if you print that you need 'em.
The actual res of a monitor varies depending on it's size, and the screen resolution, e.g., your average 17" CRT set to 1280 x 1024 will display approx 100dpi, and a 15" laptop screen running at 1600x1200 will be higher still.
Ex-biker said:
So do all Dslr's store files at 72ppi?
No, my D70 files say '300dpi'.
Ex-biker said:
So if you are submitting a pic for print you need to resample it to 300ppi in Photoshop?
All you'll get is a much smaller image...
Think of this: Each of your images will be (rounded down for ease of maths) 3000 x 2000 pixels. If you make a print that's 10" wide, it will be 3000/10 = 300ppi. If you make it 20" wide it will be 150ppi; if you make it 5" wide it will be 600ppi. (Not that the eye can resolve even 300dpi).
Ex-biker said:
So do all Dslr's store files at 72ppi?
just forget about what comes out of your DSLR, it's 100% irrelevant. I don't know which camera you have, but if it produces a picture which is 3000x2000 pixels, it does not matter whether it is saved at 1DPI or 999,999,999,999,999DPI. They will both be 3000x2000 pixels, and will both be identical.
Ex-biker said:
So if you are submitting a pic for print you need to resample it to 300ppi in Photoshop?
there is no point in changing the nominal resolution of a picture in photoshop by itself. Like I said above, your 3000x2000 picture will be no different no matter what resolution you say it is.
where this becomes important is when you are using the crop tool set to a particular size, for example 18"x12". You will see next to where you input the dimensions for your crop at the top there is also a box for "resolution". Because you are specifying a physical size, the final picture will come out differently if you set it to 100DPI (1800x1200 pixels) than it will if you set it to 300DPI (5400x3600)
HTH
PS. Where I say DPI it is interchangeable with PPI
At 3456x2304 (best resolution out of camera) the image is sized at 121x81cm (big), but 72ppi
I can resize it without changing the ppi by unticking the 'resample image' box in Photoshop resize image.
This gives me 29x19cm at 300ppi (still 3456x2304)
Isn't this small for an 8mp camera? (Canon 350D)
I can resize it without changing the ppi by unticking the 'resample image' box in Photoshop resize image.
This gives me 29x19cm at 300ppi (still 3456x2304)
Isn't this small for an 8mp camera? (Canon 350D)
Ex-biker said:
At 3456x2304 (best resolution out of camera) the image is sized at 121x81cm (big), but 72ppi
I can resize it without changing the ppi by unticking the 'resample image' box in Photoshop resize image.
This gives me 29x19cm at 300ppi (still 3456x2304)
you said it right there - it's still 3456x2304 pixels, i.e. by changing the "size" of the image you have not actually altered the picture at all. It has made *ZERO* difference, so there's not a lot of point in doing this.
Ex-biker said:
Isn't this small for an 8mp camera? (Canon 350D)
not sure what you mean by this - all 8mp cameras (assuming the same aspect ratios) will produce pictures of the same pixel dimensions, and so will produce 300PPI prints at 29x19cm
>> Edited by dcw@pr on Wednesday 20th April 18:54
simpo two said:
All you'll get is a much smaller image...
Ex-biker said:
At 3456x2304 (best resolution out of camera) the image is sized at 121x81cm (big), but 72ppi...This gives me 29x19cm at 300ppi (still 3456x2304)
Told ya
So as you've discovered, until you print the fecker onto paper, ppi means sod all. Because files aren't measured in inches. You have X x Y pixels making Z Mb. That's it.
Looks like we could do with an FAQ on this one, as it does appear to come up quite a lot.
Funny, no one has said I have a 35mm film camera, does anybody know what size the prints will come out of it?. It really is the same thing.
dpi is the same as the height of the negative on the projector when printing traditionally. The negative doesn't change in any way. It can't!
Funny, no one has said I have a 35mm film camera, does anybody know what size the prints will come out of it?
. It really is the same thing. dpi is the same as the height of the negative on the projector when printing traditionally. The negative doesn't change in any way. It can't!
daydreamer said:
Looks like we could do with an FAQ on this one, as it does appear to come up quite a lot.
Funny, no one has said I have a 35mm film camera, does anybody know what size the prints will come out of it?
dpi is the same as the height of the negative on the projector when printing traditionally. The negative doesn't change in any way. It can't!
Best explanation I have ever heard !!!
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