Best DPI for printing to A4 (1 Viewer)

mike from ebbw · May 8, 2007

Hi guys.Anyone know what is the best DPI for printing to A4?Also would I be able to take some of the pics from my gallery and upsize them without them looking "blocky" after printing?I erased the originals doh!Thanks,Mike.

Roy C · May 8, 2007

mike from ebbw said:
Hi guys.Anyone know what is the best DPI for printing to A4?Also would I be able to take some of the pics from my gallery and upsize them without them looking "blocky" after printing?I erased the originals doh!Thanks,Mike.

Hi Mike, Between 200 and 300 dpi is reckoned to be best which means that a 800 pixel image on the longest side would give a print of 4" at 200 dpi. Even if you printed at 150dpi you are still only going to get a 5-6" print. Upsizing would not give you good quality IMO.
To get a decent A4 print you should be looking at the longest side being aroung 2300 pixels minimum.

mike from ebbw · May 9, 2007

Thanks Roy.

pe'rigin · May 9, 2007

Mike,

Depending on your printer (the better the printer the higher image file size you'll need), on average if you can get a file size of about 5-10Mbs, you'll get a good inkjet print @ A4. Try to get the image to print at its same size, ie 100%. You can crop and reposition for composition to achieve this, as long as you maintain enough Mbs.

Also worth checking in your instructions whether to convert to CMYK.

Roy C · May 9, 2007

pe'rigin said:
Mike,

Depending on your printer (the better the printer the higher image file size you'll need), on average if you can get a file size of about 5-10Mbs, you'll get a good inkjet print @ A4. Try to get the image to print at its same size, ie 100%. You can crop and reposition for composition to achieve this, as long as you maintain enough Mbs.

Also worth checking in your instructions whether to convert to CMYK.

Mike is asking if he can get a A4 print from images his images in the BF gallery which will probably be between 100-200 kb (he has deleted the originals by mistake) which is why I explained that 800 x 533 pixels images will only give him a 5 or 6 " print even if he prints at 150 dpi.

RAH · May 9, 2007

Don't really understand why the size of the file is meaningful, pe'rigin. As Roy says very clearly, it is the DIMENSIONS of the image (width and height in pixels) that is the critical factor. I agree with Roy's guidelines (200 dpi, etc). You just do the math and you know how large you can successfully print.

normjackson · May 9, 2007

mike from ebbw said:
I erased the originals doh!

Dunno about "doh" I would (and do) feel more like:'D

You can get software to upsize pictures without them looking "blocky". However there will likely be introduced some other issue such as bluriness, some sort of artifacting or maybe the result looking a bit like a painting. Depending on how much you magnify and from how far you view the print you may or may not get acceptable results. Sharp detailed starting material (such as your great tit picture) is also a help.
Was thinking of trying out a few upsizing software demos haven't tried before (including Size Fixer and Alien Skin Blowup) but feel almost reluctant to ask which pictures have been deleted...

pe'rigin · May 9, 2007

It's to do with the file information and resolution.

I could have a 200dpi @ 600 x800p (1.37Mb file) which will give me a half decent 5 x 4” and a useless A4 print.

As with any printing process, initially forget dpi, and dimensions and look at the file size, because that figure will give you the indication of the extent of your printing in terms of enlargement and reproduction. Then select your dpi to suit your intended process; this gives you your enlargement factor.

By choosing 5-10Mbs-file size at 100%, I was averaging out a number, which would give an acceptable result on many inkjet printers.

Roy’s right about the dimensions, but what we can’t do is up the dpi and expect the quality to improve. You can only print from the data within that file.

Mike, sorry, but you’re not going to get a good result with your file size for A4.

mike from ebbw · May 9, 2007

Thanks for the input guys.I dont normally print my pics but have been asked to do a gallery for a local woodland festival.It looks like I will have to take some more pics and print from the originals, before deleting them this time!Never mind,it is just another reason to get out with the camera.I tried printing out two of my pics (incl my great tit) at 8"x6" and have to say they look pretty good.I doubt if I could go much bigger though.Thanks again guys,Mike.

RAH · May 10, 2007

pe'rigin said:
I could have a 200dpi @ 600 x800p (1.37Mb file) which will give me a half decent 5 x 4” and a useless A4 print.

As with any printing process, initially forget dpi, and dimensions and look at the file size, because that figure will give you the indication of the extent of your printing in terms of enlargement and reproduction. Then select your dpi to suit your intended process; this gives you your enlargement factor.

Well, I have to agree and disagree. I agree that the number of pixels in the image is what counts and that you cannot get a good large print just by lowering the dpi.

But surely the best and easiest way to determine how many pixels are in the image is by looking at the pixel count - i.e. the dimensions - width x height in pixels. Yes, the number of pixels will be secondarily reflected in the filesize in bytes, but factors such as file format (jpg vs tif) and compression can affect the filesize and make it less meaningful. And what could be more meaningful than the actual number of pixels??

Once you know the number of pixels then you'll know whether that number will support what you want to do -e.g. print at a certain size. As you say, a 600x800 image will give a lousy A4 print, but I know that because I divide the dimensions 600 and 800 pixels by a good printing dpi (not too much less than 200) - i.e. 600/200 = 3; 800/200 = 4 - not by somehow indirectly looking at the filesize 1.37MB.

pe'rigin · May 10, 2007

RAH,

I think we will have to agree to disagree on terminology.

I base everything on file size, the first thing I do on any file image is apple_i to see the size. This immediately gives me an instant indication of what I can achieve with the image, I am looking for the final resolution capabilities from that file, pixel dimensions I have no use for at this stage, because it could be anything from 72dpi, 100dpi or 400dpi. But, what does not change is the file size.

From the size I can judge whether the file will reproduce successfully at A4 size or only enlarge to a postage stamp size.

As I have written before, you only have to open any magazine and view the bad images to see that the enlargement has exceeded the resolution capacity of the file.

Macswede · May 10, 2007

per'rigin, generally speaking I totally agree but file size depends on the amount of information in the image so a flight shot against a clear blue sky is going to have a much smaller file size than say a bird perched in a leafy tree assuming both are of the same quality. That's down to the amount of information contained in the background.

RAH · May 11, 2007

pe'rigin, yup, I agree, the filesize can be handy to quickly determine whether an image will work or not, without even bothering to open it. Good idea!

pe'rigin · May 11, 2007

Macswede,

Yep, agree, both the skyshot and treeshot is about recording information.

My point to RAH was that from looking at the file size you could get a good indication on how good it would print whatever process. From then on you decide what enlargement factor that image can take in terms of composition and final printing resolution. After that dpi is irrelevant, because it then your ability as a designer to understand just what is achievable with that file, a good designer will get the file within the correct resolution, too many don’t understand this process, and that’s why we see so much shocking work produced

The difference with digital over film is your file size against enlargement factor. With film you don’t have this because you’re set your enlargement factor to suit your design with the correct resolution and colour profile for the printing process. So, everything was produced at 100%. When these rules are followed using the digital process the quality is infinitely better than pre-computers. But, looking at certain books produced in the 70s and 80s, we have yet to match the quality with all our modern equipment and that is purely down to a lack of knowledge.

mjmw · May 11, 2007

pe'rigin said:
RAH,

I think we will have to agree to disagree on terminology.

I base everything on file size, the first thing I do on any file image is apple_i to see the size. This immediately gives me an instant indication of what I can achieve with the image, I am looking for the final resolution capabilities from that file, pixel dimensions I have no use for at this stage, because it could be anything from 72dpi, 100dpi or 400dpi. But, what does not change is the file size.

From the size I can judge whether the file will reproduce successfully at A4 size or only enlarge to a postage stamp size.

As I have written before, you only have to open any magazine and view the bad images to see that the enlargement has exceeded the resolution capacity of the file.

I think I hear what you are saying but the filesize has nothing to do with what resolutions are possible...as RAH points out it is to do with pixel dimensions. Take the following example:

The attached image has an average mix detail, is 720x480 pixels and as an uncompressed TIFF is about 1mb in file size.

Add 5 or 6 adjustment layers and resave as uncompressed TIFF and the file is now twice the size...but it is still only 720x480 pixels.

This difference is even further exagerated by full-size images in PSD format.

If we all used the same file format, with the same OS, same versions of software and EXACTLY the same post processing techniques then file size may be a useful general indicator of resolution. However, even in my own files using the same workflow, same software etc, each image I process may have a slightly different set of post-processing steps applied and therefore the file-sizes of identical resolution images could be vastly different.

mjmw · May 11, 2007

pe'rigin said:
The difference with digital over film is your file size against enlargement factor. With film you don’t have this because you’re set your enlargement factor to suit your design with the correct resolution and colour profile for the printing process. So, everything was produced at 100%. When these rules are followed using the digital process the quality is infinitely better than pre-computers. But, looking at certain books produced in the 70s and 80s, we have yet to match the quality with all our modern equipment and that is purely down to a lack of knowledge.

Not sure I follow this - why is it any different today between digital and film? Surely the resolution of the image is and was limited by the processes available to resize and print?

pe'rigin · May 11, 2007

Mark,

The increase in size for a PSD_file is through the adding of layers.

I can have an A4 file, at 60Mb at 300dpi, add 40 layers and my file size will go through the roof, but it still tells me it’s a PSD, when I flatten that file I still have an A4 file at 60Mbs at 300dpi. I have not gained a 1Gb sized file.

The difference between digital and film is:-

Once you fire the shutter on a digital, that's it, all your data, enlargement factor is locked within the file.

Think of it as an elastic band, if you stretch (enlarge) the band it degrades the rubber, same with digital files. If you scrunch up (reduce) the band you loose nothing.

Film you choose what you want to do, enlarge 400%, 600% at whatever resolution you want, etc.

Quality wise digital is going to get better and better, but, I used to shoot 10x8” colour trannies and nothing in the digital world comes remotely near that quality.

hollis_f · May 11, 2007

I'd never try using file size to try to determine how large a picture could be printed. I have here two images, both are 3520x2346 pixel jpegs. I'd happily print either of them at A4. However, one is 140kB and the other is 8,706kB. That's a 62-fold difference in file size. Even the resampled images show a 50-fold difference.

Yes, they are extreme examples. But it does show how a change in the amount of detail in an image combined with different compressions can have huge effects on file size,

mjmw · May 11, 2007

pe'rigin said:
Mark,

The increase in size for a PSD_file is through the adding of layers.

I can have an A4 file, at 60Mb at 300dpi, add 40 layers and my file size will go through the roof, but it still tells me it’s a PSD, when I flatten that file I still have an A4 file at 60Mbs at 300dpi. I have not gained a 1Gb sized file.

You have got a 1 gb file - the file size is 1 gb - but I agree that the image resolution has not changed, which was my point. You can not know how many layers there are in the PSD, TIFF or whatever format from the size, so the file size tells you nothing about resolution and therefore the size you can print.

pe'rigin said:
The difference between digital and film is:-

Once you fire the shutter on a digital, that's it, all your data, enlargement factor is locked within the file.

Think of it as an elastic band, if you stretch (enlarge) the band it degrades the rubber, same with digital files. If you scrunch up (reduce) the band you loose nothing.

Film you choose what you want to do, enlarge 400%, 600% at whatever resolution you want, etc.

Quality wise digital is going to get better and better, but, I used to shoot 10x8” colour trannies and nothing in the digital world comes remotely near that quality.

Still not following what you are saying - you are still limited by the resolution of the starting point. Yes, if you want to compare apples and oranges, you can enlarge a 10x8" to a greater size than a 'normal' digital image...but you can also enlarge it more than say 5x4" or 35mm transparencies.

A transparency has a maximum enlargement size which depends on the output media, whereas you can think of a digital file as already being at that largest size - you just vary the DPI to maintain the physical dimensions (not pixels) to match the output media. If you enlarge the transparency beyond that 'best maximum' point, it will degrade, just like enlarging a digital file does.

mike from ebbw · May 11, 2007

Thanks for all your time and input guys but I am completely lost now!I tried upsizing and printing one of my gallery images to A4 and it was rubbish(unsurprisingly).I have kept a few of my decent shots full size and printed them to A4 and I am very pleased with them.I think I have learned my lesson.If there are any shots worth keeping put them on a disk at full size.Thanks again,Mike.

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