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File Size For A6 Print? (1 Viewer)
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RAH
Well-known member
Yes, there is a formula - 200 dots per inch (also called pixels per inch). I don't agree with the earlier posting which says 300. You do need 300 dpi for publication media (like for magazines), but for inkjet printing, 200 dpi is all you need.tracker said:
What this means in terms of file size is very simple. It's the dimensions of the image that are important, not the filesize in bytes. So, for example, if you take an image with a digital camera that is 2036 pixels x 1536 pixels, you just divide each number by 200 (pixels per inch), to find out the largest print you can make and get good quality. In this example 2048/200 = approx 10; 1536/200 = approx 8; so the largest print you can make from a 2048x1536 image is 10 x 8.
For an A6 print (about 4 inches x 6 inches), you need an image size at least about 800 (4 x 200) x 1200 (6x200). This is a pretty low res picture, about what you get out of a 2MP camera.
You set the dpi of an image in your image editor, usually in the resize tool, but make sure to NOT use resample. Resample will alter the dimensions. What you want is to alter the dots per inch that it will print at WITHOUT affecting the dimensions. This is a resize WITHOUT resample.
tracker
Tom
Thanks for the info, Rob and RAH, much appreciated. 
Not sure what it is, but Ive just not managed to get my head around digital printing, and the various combinations of file size and final print quality.
RAH, during (i think its called) interpolation, is this a reliable way to get a good quality print, or is there a lowering of the final print quality?
For example, I have an image that is 350kb at its maximum size (700x500) at 72dpi.
If I change the dpi to 300 the pixel dimensions change from 700x500 to 2917x2083.
Can I get a good quality A6 print from an image that is 350kb? Do I need to interpolate to achieve this?
Apologies if Im taking a while to grasp this :stuck:
Not sure what it is, but Ive just not managed to get my head around digital printing, and the various combinations of file size and final print quality.
RAH, during (i think its called) interpolation, is this a reliable way to get a good quality print, or is there a lowering of the final print quality?
For example, I have an image that is 350kb at its maximum size (700x500) at 72dpi.
If I change the dpi to 300 the pixel dimensions change from 700x500 to 2917x2083.
Can I get a good quality A6 print from an image that is 350kb? Do I need to interpolate to achieve this?
Apologies if Im taking a while to grasp this :stuck:
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RAH
Well-known member
"Interpolation" usually means enlarging a picture (i.e. increasing its height and width - its dimensions). Such an operation degrades the quality of the image because it manufactures pixels out of thin air and adds them to the image. There are some specialized plugin tools that purport to do a good job, and some folks say if you do it in little increments you get better results. However, you can only do it up to a point.tracker said:
Changing an image from 700x500 to 2917x2083 is a HUGE increase in size. Your starting image is awfully small. But I don't understand why you want to increase it so much. As I said in my earlier note, to get an image that will print nicely on A6, you need an image that is 1200 x 800.
Soooo, just increase its size from 700x500 to 1200x800, which will probably work OK. In such an operation, it is much clearer if you use the pixel count, not the dpi, to determine the settings in the image program. In other words, you know you want 1200, so in the dialog box, put 1200 into it (have it set to maintain the image's height/width ratio), make sure that resample is checked, and that's it.
Finally, saying that an image is 350kb is kind of meaningless. It depends on whether it is jpg or a tif, how much compression was used, etc, etc. It tells you nothing about how big the image is and how it will print. Again, it the height and width in pixels that matter. And that is all that matters.
tracker said:
For a print that looks good you need between 7 and 10 dots per mm which gives you a max of 1050x1485 for an A6 print. This is about 1.5megapixels. If your camera is giving you a jpeg that is 350kb then it is likely that your camera is of a higher definition than 1.5mp, my 1.3 mp Olympus gives me Jpegs of abot 250k, though my 6.1mp canon gives me jpegs that are 2.5mb. With the 1.3 mp camera I was quite happy to print at up to A5 ( with small margins ) and anyone would have been hard pushed to grumble at the quality of the pictures, mind you if you get a magnifying glass on them you might see small problems. I even printed on A4 from the 1.3mp and was reasonably happy with the results.Printing on 6x4 you are unlikely to have any problems with any reasonably modern digital camera. My 1.3mp camera is an Olympus 920z which I have had since 2001, anything more modern is unlikely to have any less megapixels.
robski
Well-known member
Tom
Your 500 x 700 will be 1Mb uncompressed. I was assuming you were going to get a photo print done as opposed to doing an inkjet. I don't know why people bother with inkjet prints when 6 x 4 photo prints can be as cheap as 7 pence each if you get a batch done.
Inkjet is so expensive by the time you have add up all the costs. Then there is no gaurantee you will get a good print because the head needs cleaning.
Your 500 x 700 will be 1Mb uncompressed. I was assuming you were going to get a photo print done as opposed to doing an inkjet. I don't know why people bother with inkjet prints when 6 x 4 photo prints can be as cheap as 7 pence each if you get a batch done.
Inkjet is so expensive by the time you have add up all the costs. Then there is no gaurantee you will get a good print because the head needs cleaning.
RAH
Well-known member
I believe that the "200 rule of thumb" also applies for getting photo prints made. It's only if you are going to have an image printed in a magazine or other type of publication that you need 300, as I understand it.robski said:
I agree that you do have to mess around a lot making your own prints, with trial and error, head cleaning, etc. But after awhile you get used to it, I find.
tracker
Tom
Hi,
Once again thanks for all the advice.
The file that is 350kb is as a result of me shooting at a very low setting on my coolpix 4500 ( if i remember correctly - that was about 18 months ago ) Ive learned a big lesson since then.
My intention is to use a shop to print my pics, but I do have a decent printer and would like to understand the principles discussed above much more clearly.
I mainly shoot with a canon 20d and know I can get decent sized images with that; and from the info you guys have supplied, I now see the importance of starting off with an image with the correct dimensions ie 2048x1536 etc, as opposed to trying to stretch a smaller sized pic.
Thanks again
Once again thanks for all the advice.
The file that is 350kb is as a result of me shooting at a very low setting on my coolpix 4500 ( if i remember correctly - that was about 18 months ago ) Ive learned a big lesson since then.
My intention is to use a shop to print my pics, but I do have a decent printer and would like to understand the principles discussed above much more clearly.
I mainly shoot with a canon 20d and know I can get decent sized images with that; and from the info you guys have supplied, I now see the importance of starting off with an image with the correct dimensions ie 2048x1536 etc, as opposed to trying to stretch a smaller sized pic.
Thanks again
robski
Well-known member
As Bill has pointed out (maybe without realising it ) the limits of the human vision system is around 7 to 10 lines per mm. Which is in the range of 180 to 260 pixels per inch. I would err on the mid 200's at least. For magazines they use halftone screening and print photos in range of 150 to 200 lpi dependent on how good the printing press is. When using halftone screening the photo pixel per inch should be atleast double the halftone setting.
i.e 300 pixels per inch for a 150 lines per inch halftone.
i.e 300 pixels per inch for a 150 lines per inch halftone.
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robski said:
It's called instant gratification. I rarely have 100 pictures that I want to print out at any time, but frequently have 10 or a dozen and the hassle of finding a tesco's ( or similar ) open with a machine in working order is just not worth it. We also spend quite a bit of time away in our caravan and to be able to get the picture mate out each evening and look at the pictures we have taken is part of the holiday.
As to head cleaning, if the printer has not been used for some time then we print a test sheet out and if necessary use the cleaning cycle before we try any picture printing, it's never a problem.
Prints
Forgive me for jumping in but as a newbie to all this perhaps some one could put me straight on a couple of things.....
Can you get Tiffs printed instead of jpegs?
If you print at home Iv'e heard you have to have your monitor and printer profiled correctly with extra software ?
Thanks
__________
Steveps
Forgive me for jumping in but as a newbie to all this perhaps some one could put me straight on a couple of things.....
Can you get Tiffs printed instead of jpegs?
If you print at home Iv'e heard you have to have your monitor and printer profiled correctly with extra software ?
Thanks
__________
Steveps
robski
Well-known member
tracker said:
Ok Tom I know where your coming from. I've only had one batch of 6 x 4 printed as photos by Jessops. I did these at 300 pixels per inch and they were spot on. How much lower than 200 pixels per inch you can get away with I am not sure.
I went to a lot of trouble sizing them and putting on crop marks to fit a photo frame for a gift ( the 6 x 4 needed 5mm trimmed off each edge to fit) to find out they over scanned them by 2%.
I used to have an inkjet printer, I never used it enough to justify the cost ( once every 4 or 5 months ) I think the last time I used it it cost me about £5 per A4 print with all the wastage. So I chucked it in the bin. The odd time I print something I use the colour laser printer at work. It's mainly people who want a hard copy of one of my desktops so they can hang on their wall.
If I recall the machine in Jessops would take a tiff aswell as jpegs.
steveps said:
Printer will do either tiff or jpg or whatever the software you are using will allow. Mind you I've never had a problem matching monitor to printer, though for the actual printing I either use the epson photoquicker that came with the printer and does a good job of colour matching the prints, or I use the software that came with the camera which also makes a good job of sorting out the colour of the picture.
tracker
Tom
robski said:
Rob, exactly.....I too have a decent printer, but it just sits there, and believe it or not, Ive been shooting digital for 2 years now, and had my first pics done at a local chemist about 2 months ago, and I loved the quality. Seems to be the way to go. Sadly, on one pic, they cropped a little too much and messed up, but it was a learning curve for me (and them, hopefully lol) Think I was only charged 40p a print (got 10@ 8x6)
Having said all that, earlier tonight I applied the formula mentioned above, and printed out a Fox pic I have, and was pretty pleased. So things lookin up. Thanks again everyone :t:
Btw Steve, no worries at all about jumping in, feel free
Keith Reeder
Watch the birdie...
steveps said:
Not necessarily, Steve.
I've recently bought a litle Epson R220 photo printer, and - without any fiddling and faffing on my part to profile/calibrate the printer and PC, the prints are coming off absolutely perfectly - couldn't be better.
