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F200exr: why 72 dpi?
- Thread starter jobocam
- Start date
72dpi is a typical screen resolution. The camera (any camera) takes the number of pixels it does according to the sensor size and the settings in the camera menus. If I view one of my S200EXR on screen in Irfanview it reports 72dpi but that is a screen thing.
TDR1
Leading Member
I wouldn't worry about it. For printing you sometimes want to try and achieve 300dpi, but you do this by making sure that you print your image at the right physical size on paper to match the resolution of your image. For example if it's only a 300x300 pixel image, to get 300dpi you would print it at 1inch by 1 inch.
The DPI value embedded in the image doesn't really affect this and is only sometimes used as a pointer to the DTP package to tell it what size to initially display it at.
The important thing to remember is the dimensions of the image. Simply divide the height and width by 300 and that tells you what the maximum size you can print at to achieve 300dpi.
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TDR1
http://gallery.net11.co.uk/
http://www.flickr.com/photos/tdr1/
The DPI value embedded in the image doesn't really affect this and is only sometimes used as a pointer to the DTP package to tell it what size to initially display it at.
The important thing to remember is the dimensions of the image. Simply divide the height and width by 300 and that tells you what the maximum size you can print at to achieve 300dpi.
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TDR1
http://gallery.net11.co.uk/
http://www.flickr.com/photos/tdr1/
So, if I want to print one of my shoots (72dpi from F200EXR) not in A4 format (max size format for a 6Mp), is it not usufull to convert in 300dpi ??
If you up-sample your image, you won't improve quality - you'll just make it bigger. Think of this - if you camera produces 72 dpi then in one inch horizontally you have 72 dots. These dots are originals from the image. If you ask software to up-sample the image to, say, 144 dpi then you need twice as many dots in an inch. The algorithm that up-samples the image will make assumptions about what to do. If your original image has the following pixel colours in a row:
RGBBGR
then the software has to decide how to double the six pixels to twelve. Maybe it will do this
RRGGBBBBGGRR - or maybe it will do this
RGGBBBGGGRRR
there are many different sampling algorithms and they will all do something different. They all make assumptions but none of them is necessarily a true reflection of the original image - because what you really want (in this example) are 144 dots from the original image rather than 72 from the original and 72 made-up dots. If you take this to an extreme and up-sample an image by a long way, you get what is termed a blocky image - one where the smoothness of the original is lost and the rectangular oversized pixels can be seen. So, it is best to avoid up-sampling if at all possible.
When you send an image with 72dpi to a printer which is set to print at 300dpi and ask it to print at the original size (that last bit is the vital bit) then the printer will make assumptions on how to fill in the missing dots. If you send your image at 72 dpi and ask it to print it at a quarter the original size (again, the last bit is important) then the printer will have an image that is not at 72 dpi but at four times that: 288 dpi (which is very nearly 300 which is a typical printer resolution) and it will have to make very few assumptions.
But this may all be academic. My Fuji produces 96 dpi and if printed at original size, will produce an image 37 inches by 25.3 inches. If I print this image on an A4 sheet of paper (approx 12" by 8") then the image is reduced by a factor of three so the dpi is increased by a factor of 3 and I end up with an effective resolution of very nearly 300 dpi. If I print this on an 8x5" then the dpi goes up further.
The question is ... what size do you want to print out your images?
Thanks for your time 
What size? ok... let me do a chart...from my 72 dpi (F200exr at 6Mp) I want for example these common format :
1) 10x15cm
2) 13x18cm
Do I have to transform up to 300dpi? this kind of transformation (at 300dpi) is good only if I print an A4 (max size for 6Mp)?
Thanks again.
What size? ok... let me do a chart...from my 72 dpi (F200exr at 6Mp) I want for example these common format :
1) 10x15cm
2) 13x18cm
Do I have to transform up to 300dpi? this kind of transformation (at 300dpi) is good only if I print an A4 (max size for 6Mp)?
Thanks again.
I assume that you are shooting in M 4:3 and this has a resolution of 2,816 x 2,112.Thanks for your time
What size? ok... let me do a chart...from my 72 dpi (F200exr at 6Mp) I want for example these common format :
1) 10x15cm
2) 13x18cm
Do I have to transform up to 300dpi? this kind of transformation (at 300dpi) is good only if I print an A4 (max size for 6Mp)?
Thanks again.
If you want to print at 300dpi then 2,816 divide 300 equals 9.3" and 2,112 dpi equals 7.04" so the largest photo you can print is roughly 9" x 7".
1) You want to print at 10x15cm (which is 3.9" x 5.9") and this is smaller than 9" x 7" so you will get more than 300dpi resolution going to the printer.
2) You want to print at 13x18cm (which is 5.1" x 7") which is also smaller than 9" x 7" so again, you will get more than 300dpi resolution going to the printer.
Try it out ... if you are happy with the results then all is well.
joseph costa
Leading Member
you can print whatever size and whatever dpi level you like. the more dpi typically, the better it may look especially at larger sizes....however, because of viewing distances, you're just wasting ink at that point. when i get my 30 x 40 inch prints done, they're usually at about 170dpi to 200dpi. i don't require any more than that.
Happy Shooting!
-J. Costa
Happy Shooting!
-J. Costa
So, if I have understood, for my print format at 10x15cm or 13x18cm I can let 72dpi cause increasing at 300dpi is not a quality improvement, right?
Thanks again and sorry for my "slow mind" ;-)
Hi, I don't bother with any of this calculating or converting. Have a look at Qimage - http://www.ddisoftware.com/qimage/
It does what it says on the packet. Works with any printer. You can download a trial before you pay for it. I would not use anything else.
It does what it says on the packet. Works with any printer. You can download a trial before you pay for it. I would not use anything else.
Just ignore the 72 dpi value added to pictures by the camera, it has absolutely no meaning for print. Before printing only crop the picture (without resampling) to the required aspect ratio, if needed. 12 megapixels is more than enough resolution for 10x15 and 13x18. Most digital minilabs print at 300 dpi, so you can print a 33,8cm x 25,4cm photo in "1:1" quality from a 12 MPix image.
Billx08
Forum Pro
You're making way too much of 72 dpi. It's not a real value that has much significance. As has been written earlier, it's a hint from Fuji to the image display software that you use on your computer telling it how large to initially display your camera's images on the screen. The camera could have defaulted to 0 dpi or 240 dpi without changing the image in any other way. You'd be much better off forgetting about the camera's 72 dpi default entirely.
If you want to print at a particular dpi just go by the number of horizontal and vertical pixels and the height and width you want to print at. That determines the dpi that will be used for your prints. If you want to print at 300 dpi, just divide the image's pixel dimensions by 300, which will show you the actual print size. If this is slightly smaller than the print size you want to achieve, either choose a smaller dpi (such as 240 dpi) or keep it simpler by having the software make the print the size you want, and it will adjust the dpi for you.
You should probably also understand that 300 dpi isn't the gold standard . Many people can't see any difference between prints made at 240 dpi and 300 dpi. Some have better eyes and claim to prefer prints made at 400 dpi. Irregardless of the dpi used, differences won't be seen beyond a certain viewing distance, so for critical use, that should also be taken into consideration. As an experiment, prepare a 100% crop (to keep from wasting paper on large prints) and make several prints using 120, 150, 200, 240, 300 and 400 dpi. See which is best for your purposes and the point of diminishing returns.
John Carson
Senior Member
The dpi reported is completely irrelevant for printing and should be ignored.
Your photos are simply a rectangular array or "grid" of pixels. There is no such thing as a 72 dpi array of pixels or a 300 dpi array of pixels. A rectangular array of pixels is a rectangular array of pixels is a rectangular array of pixels. That is all there is.
The 72 dpi value is simply an entry in a "header" that is attached to the pixel array. In principle, that dpi value could be changed to anything you like with no change whatsoever to the actual image that is stored. The purpose of the dpi value in the header is to act as some sort of "recommended" dpi to be used for display purposes (for a given image, different dpi values lead to a different size of the displayed image --- doubling the dpi halves the height and width of the displayed image). In practice, almost all software ignores the recommendation and your printing software certainly will.
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john carson
Kim Letkeman
Forum Pro
Every camera seems to choose s different value in that field. It is almost completely meaningless for people who never print, or who print at home.
Your printer driver will allow you to click on boxes like "fit to media" and that kind of thing. You can also select enlargement amounts etc.
If you print outside, you might want to set the correct value in there. 300ppi is the the native resolution for the Fuji Frontier printers that are used in places like WalMart and Costco.
360ppi is the native resolution of most Epson printers, 300ppi of most others. You can figure that out by reading your printer manual.
If you want to be really precise about sharpening (and you should), you will want to size a copy of your image specifically for printing (e.g. the right ppi for the specific target media for this one copy), then set the ppi in the photoshop resize dialog and allow it to interpolate to create the final number of pixels. Then you sharpen specifically for that size and type of output.
For a really good treatment of these issues, read "real world image sharpening" by the late Bruce Fraser. I think Jeff Schew updated it since his death.
Here is a link into an article series on Adobe Press that are taken from the book:
http://www.adobepress.com/articles/article.asp?p=608637
--
http://kimletkeman.blogspot.com
http://letkeman.net/Photos
Your printer driver will allow you to click on boxes like "fit to media" and that kind of thing. You can also select enlargement amounts etc.
If you print outside, you might want to set the correct value in there. 300ppi is the the native resolution for the Fuji Frontier printers that are used in places like WalMart and Costco.
360ppi is the native resolution of most Epson printers, 300ppi of most others. You can figure that out by reading your printer manual.
If you want to be really precise about sharpening (and you should), you will want to size a copy of your image specifically for printing (e.g. the right ppi for the specific target media for this one copy), then set the ppi in the photoshop resize dialog and allow it to interpolate to create the final number of pixels. Then you sharpen specifically for that size and type of output.
For a really good treatment of these issues, read "real world image sharpening" by the late Bruce Fraser. I think Jeff Schew updated it since his death.
Here is a link into an article series on Adobe Press that are taken from the book:
http://www.adobepress.com/articles/article.asp?p=608637
--
http://kimletkeman.blogspot.com
http://letkeman.net/Photos
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