digital image size to print size?

louise-knight

louise-knight

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Louise Knight
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This may have been asked a million times before, I've just done a quick search on the forums and google, but haven't found exactly what I'm looking for.

I was just wondering if anyone can link me to a chart which shows what pixel size an image has to be to be able to print at which sizes?

Thanks :)
 
I guess you could find such a chart but it is really down to what is an acceptable quality at the viewing distance. You could probably blow a 1 megapixel image up to the size of a billboard and it would look great from 100 yards away :)
 
I'm sure you divide the image pixel width/height by the resolution to get the print size.
 
On Roberts point again, just adding for interest. Apart from standard size enlargements its important to realise it is the sharpness of the original pin pricks of light that make up the sharp part of your images that will cap the limit of the images sharpness when enlarged.
(depending on viewing distance but based on a normal view)

So you should find your truly sharp images will go larger.
 
when we do printing at work, we have 2 companies and they give us:

25% of final image size

or

1/10th scale (200cmx200cm would be 20cmx20cm)

clear as mud.
 
I think the optimum recomended dpi is 300 for printing. :thumbs: Not sure if thats what your after
 
local photoshop here has a large canvas of a flower for demonstration purposes, maybe 3ftx2ft, which is off a 3MP image and looks great. Obviously one tends not to view an image of that size at 10".
 
I go with pearce jj.

I use 1 1D mkII which is 'only' 8MP but have successfully blown the pictures up to a height of 6 feet, because at that size you step back to look at it.

Is it totally perfect at 10 inches? no of course not, but check out bil boards as mentioned earlier, and neither are they
 
I've done A4 prints from a 3MP compact that look fine, even at relatively close distances and A3+ prints from a 6MP DSLR look fine too. As Forbiddenbiker said above, a good, sharp image will be happier at large enlargements than a poor one.
 
Thanks for all the replies :)

I don't generally want to blow them up to huge scales.. The reason I'm asking is that I'm putting some work up for sale in a shop, and an image I took had too much going on to one side (coastal sunset with houses on the right of the shot), so I cropped the houses out and the composition looked pretty good, but because of the crop, I'm not sure how far it'll go for print.. I only want to print at 10x15inches, and I think this shot was on the 450D, which is 12.2mp.. maybe (I should know this really..!) I think I'll give it a go at jessops first at that size, just to check out the quality.. they're prints are only £4 a pop..!

Thanks very much :)
 
louise-knight said:
Thanks for all the replies :)

I don't generally want to blow them up to huge scales.. The reason I'm asking is that I'm putting some work up for sale in a shop, and an image I took had too much going on to one side (coastal sunset with houses on the right of the shot), so I cropped the houses out and the composition looked pretty good, but because of the crop, I'm not sure how far it'll go for print.. I only want to print at 10x15inches, and I think this shot was on the 450D, which is 12.2mp.. maybe (I should know this really..!) I think I'll give it a go at jessops first at that size, just to check out the quality.. they're prints are only £4 a pop..!

Thanks very much :)
Click to expand...

Take the numebr of pixels in each axis of your image and divide by the size you want to print each axis.

Lets say you have 2000 x 3000 pixels. and you want a 10"x15" print.

2000/10 = 200
3000/15 = 200

You would be able to print the image at 200ppi. This is perfectly acceptable for a 10x15 inch print. Many advise going for 300ppi but honestly the 200ppi would be plenty.

If you find your resolution lower, you could resample the image a bit.

Can you provide more detail?
 
that's about it really
divide the size of the pic in pixels by the DPI used in the printing process

i doubt jessops print at 300dpi anyway but they should be able to tell you

UK magazines always print at 300dpi hence the need for large/sharp images and newspapers around half that

for my two penneth resampling or interpolation never works if the image is too small
 
There are a number of factors to consider. I've had images printed at fairly large sizes ( 20 x 30 inch) from a 6Mp camera. It's really how how treat the image that makes a lot of difference.

Natural image sharpness ( i.e. not one that has loads of PP sharpness added) makes a huge contribution to the final result. As does any post capture sharpening you add. If you are having the print produced commercially be careful not to over sharpen, as this can give a very grainy effect, with sharpening on top of sharpening.

If you have your own inkjet printer, make a proof image of the crop you want. If you final print is bigger than you printer can produce, simply print an area at the appropriate magnification and see how it looks
 
At 300dpi (the highest agreed standard) for a 10x15in print you need 13.5m pixels. This reduces dramatically for smaller sizes, like 6.3m for a 10x7, and a mere 2.2m for 6x4.

But there is far more to it than pixels, like viewing distance and image contrast. I doubt that any DSLR camera can ever deliver 13.5m pixels from corner to corner of a print, lenses just can't deliver that much resolution, but you will still get a sensationally sharp image from a far smaller file size.

I think a key factor will be the quality of your post processing. If you have a decent image to begin with and really know how to tweak the sharpness, contrast and other levels, you should get a very good print.
 
photobiker said:
that's about it really
divide the size of the pic in pixels by the DPI used in the printing process
Click to expand...

No - divide each axis of the image size in pixels by the resolution of the image (ppi)

The resolution of the print is totally different - I print at 2880x1440 dpi. dpi is not the same as ppi.

photobiker said:
i doubt jessops print at 300dpi anyway but they should be able to tell you
Click to expand...

If they use a modern printer they probably do use a 300dpi machine - new machines from Fuji I think use 6000dpi.

Remember it's pixels you are measuring here. Forget the dpi of the PRINTER what you need to consider is the number of pixels in your image.

If you want a 6x4 print from say a web image with 432pixels x 288pixels, you need 72ppi to get tyhat 6"x4" print (without interpolation) I can still send that image to my printer at 300dpi.

Pixels per inch will determines the size of the printed image and the size of the printed pixels. - The smaller the pixel size (at a consistent print size), the higher the resolution will be.

Dots per inch determines the resolution of the printed image. Printing a 72ppi image is still likely to look bad (unless its a very large print)

I'm not sure if magazines are printed at 300dpi? You may be right - but the resolution of images is a totally separate matter.
 
The best resolution our eyes can see looking closely is 300dpi.
If you have photoshop, open it and select:

Image - Image size

Insert 300 in the resolution field and the dimensions you want to print. Then you can see if you need do interpolate or not.

Take in account 300 dpi is the optimum resolution for close inspection. If you are printing for billboards or something like that, 72dpi or less is enough, depending on the size.
 
HoppyUK said:
At 300dpi (the highest agreed standard) for a 10x15in print you need 13.5m pixels. This reduces dramatically for smaller sizes, like 6.3m for a 10x7, and a mere 2.2m for 6x4.
Click to expand...

None really prints at 10"x15" or 10x7? These are not standard sizes - Although your numbers are correct.

Although 300ppi (pixels per inch) is a standard high res image for print, you don't need that for larger images (like a 10"x15"). 240ppi or even 200ppi will give a perfectly acceptable high res print. Which is what I think you were also getting at.
 
jimlizard said:
The best resolution our eyes can see looking closely is 300dpi.
If you have photoshop, open it and select:

Image - Image size

Insert 300 in the resolution field and the dimensions you want to print. Then you can see if you need do interpolate or not.

Take in account 300 dpi is the optimum resolution for close inspection. If you are printing for billboards or something like that, 72dpi or less is enough, depending on the size.
Click to expand...

ppi (Pixls Per Inch)

dpi is different (sorry for harping on about this)
 
EOS_JD said:
None really prints at 10"x15" or 10x7? These are not standard sizes - Although your numbers are correct.
Click to expand...

I think they are. Aspect ratio of DSLR sensors is 3x2. I had several of both 10x15in and 10x7in printed at Boots last weekend.
 
Yes that's the first time I've seen that size - These mini lab machines are nice and I saw a Noritsu machine recently that prints up to 10" x 30"! At £14k it was too expensive for me :)

The frame range for the 10x15 and 10x7 size is very limited though (cause they are not standard sizes like 6x4, 7x5, 8x6, 10x8, 16x12) :)
 
EOS_JD said:
Although 300ppi (pixels per inch) is a standard high res image for print, you don't need that for larger images (like a 10"x15"). 240ppi or even 200ppi will give a perfectly acceptable high res print. Which is what I think you were also getting at.
Click to expand...
Perhaps things are different in practice. My local print shop asked for a 300dpi image or an a3 print just yesterday....
 
Merovingian said:
Perhaps things are different in practice. My local print shop asked for a 300dpi image or an a3 print just yesterday....
Click to expand...

Yes. Because the dpi / ppi mismatch has been around for so long, many will ask for a 300dpi image instead of 300ppi. For this pupose they are interchangeable although the dpi term is technically incorrect.

I believe most ask for a 300ppi image because it is considered to be the highest res your eyes can resolve. However I prefer not to resample too much and if I have only 200ppi at the required size, I speak to the lab and normally they are fine about printing an A3 at 200ppi (or lower). There's virtually no difference that I can see. (Even at 150ppi from normal viewing distances or close up)!!
 
just for a laff i popped into Lincoln Jessops the other day and asked what resolution they printed at
"300dpi" came the answer
basically they then went onto say that any 4meg camera can produce an A3 print at that res???
when i questioned this they then said that the pixels count and the original size of the image didnt matter ???

and their process was different so pixels didnt correlate with printing process??

then said that if the pic was too small it could be easily be interpolated without any loss in quality??

at that point i lost all confidence in the knowledge i was being offered and did a 180
 
photobiker said:
just for a laff i popped into Lincoln Jessops the other day and asked what resolution they printed at
"300dpi" came the answer
basically they then went onto say that any 4meg camera can produce an A3 print at that res???
when i questioned this they then said that the pixels count and the original size of the image didnt matter ???

and their process was different so pixels didnt correlate with printing process??

then said that if the pic was too small it could be easily be interpolated without any loss in quality??

at that point i lost all confidence in the knowledge i was being offered and did a 180
Click to expand...

Well what they are saying is correct to a point. A 4MP camera could easily print to A3 and be printed at 300dpi. The image you send would be just under 150ppi. I have a 30x24 print at 150ppi printed on my epson printer that hangs on my wall and looks amazing!

When they say they can interpolate without loss, this maybe isn't 100% accurate but the RIP they use when printing is likely to be a lot more accurate than Ps.

I suppose there are limits to this though......
 
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