Paul_R
Pooh-Bah
Reged: 16/06/2006
Posts: 1968
Loc: Middlesbrough, England.
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Hi All
I wonder if someone could advise on the following, please?
I have only really been printing images to send off to my tutor (I'm doing the AP Diploma in Photography course) and usually just print the image I want to A4 paper using my Epson Photo RX620. I will carry out various adjustments in PS etc, add a border, then just print straight to A4. However, doing some reading at home and on the web I'm now wondering if I should be resizing my images before printing?
My digital camera images (Canon 400D) are around 4MB in size, 36in x 54in (according to PS) and 72ppi. Now, when I carry out various adjustments in PS I have noticed the image dimensions and resolution change to 16in x 11in and 240ppi. I then add a border using an action in PS (the action was downloaded off the web) and it changes to 13.95in x 10.12in and 300ppi. I realise the ppi will increase as the image dimensions are reduced.
My question is, should I be resizing the image myself to a size that I want to print to before carrying out any adjustments, which would at the same time increase the ppi to around 300 (although I understand that a ppi of around 240 would be sufficient, apparently) or doesn't it matter? Also, why does the image size and ppi change after I have made adjustmenst in PS?
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Regards, Paul CRIPN
http://www.pbase.com/exposethelight
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Malcolm_Stewart
Carpal \'Tunnel
Reged: 11/07/2005
Posts: 2583
Loc: Milton Keynes, UK
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Quote:
...
My digital camera images (Canon 400D) are around 4MB in size, 36in x 54in (according to PS) and 72ppi. Now, when I carry out various adjustments in PS I have noticed the image dimensions and resolution change to 16in x 11in and 240ppi. I then add a border using an action in PS (the action was downloaded off the web) and it changes to 13.95in x 10.12in and 300ppi. I realise the ppi will increase as the image dimensions are reduced.
...
Also, why does the image size and ppi change after I have made adjustment in PS?
The 72ppi is screen resolution, and this is why your images seem so large. In PS you have a choice in the Image Size dialog box. If you have the "Resample Image" box ticked, any changes you make will result in a change to the file, whereas if it's unticked, your file size will not change. The ppi figures are of little relevance, providing you don't resample.
I use PS6 and print my images on an Epson R220, or 1270 if I want A3 or A3+. I normally do any small adjustments in PS6, apply USM, and then select the printer and paper size using the Print Setup in PS6, followed by Print Options, where I size and decentre the image to get the effect I'm looking for. Print Preview is turned on in the R220 Printer Driver, and after hitting the print button, I get a preview which occasionally indicates that the cropping isn't quite what I wanted, so I can either Print or Cancel and adjust.
I'm sure others here will have different routes to their final print, but this works for me.
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Malcolm Stewart
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Paul_R
Pooh-Bah
Reged: 16/06/2006
Posts: 1968
Loc: Middlesbrough, England.
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Hi Malcolm,
Thanks for your reply. OK on the 72ppi being the screen resolution but don't I need to increase this to around 300ppi if I want to print the image out? This is what is confusing me!
In the book I am reading it states that a resolution of 72 ppi is considered 'low resolution' and is ideal for photos that will only be viewed on screen such as websites etc, but is too low to get high-quality prints. A resolution of 200-300 ppi is required for good-quality prints. Apparently you can't just type in the resolution so need to turn off 'Resample Image' first and then either change the physical size of the image (reduce from 36x54 inches to increase the resolution) or enter the resolution to somewhere between 200-300 ready for printing.
I have access to CS2 and Elements 6 so I can use either 
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Regards, Paul CRIPN
http://www.pbase.com/exposethelight
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Malcolm_Stewart
Carpal \'Tunnel
Reged: 11/07/2005
Posts: 2583
Loc: Milton Keynes, UK
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Quote:
Hi Malcolm,
Thanks for your reply. OK on the 72ppi being the screen resolution but don't I need to increase this to around 300ppi if I want to print the image out? This is what is confusing me!
In the book I am reading it states that a resolution of 72 ppi is considered 'low resolution' and is ideal for photos that will only be viewed on screen such as websites etc, but is too low to get high-quality prints. A resolution of 200-300 ppi is required for good-quality prints...
Which is all true. (I think the 300ppi is based on magazine printing using high quality photogravure screens. Inkjets are much more accommodating, and can produce good quality prints from lower apparent resolutions.)
I can't remember when I last instructed PS to resize an image for printing. What I think happens, is that the printer driver/PS does resizing behind the scenes, and without altering your original file. (It doesn't resample and you are limited to how large a print you can make, without pixellation showing.)
You could always try two routes and see if you can spot any differences between the prints. If you want to make really large prints, there are uprezzing applications which may help, but I'd suggest a web search before spending any money.
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Malcolm Stewart
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john_g
Pooh-bah Hoo-ha
Reged: 09/05/2007
Posts: 2536
Loc: Surrey
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I don't know the answer, but I've never resized a photo for printing at home - I've always assumed that the printing process uses all the available resolution and either squashes or stretches the image to fit the chosen print size. On the other hand I recently had a print done by a specialist print studio and they wanted my image resized to my chosen print dimensions at 300 ppi.
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John
Who could suppose that angels move the stars, or be so superstitious as to suppose that because one cannot see one's soul at the end of a microscope, it does not exist?
R.D.Laing The Politics Of Experience
http://www.flickr.com/photos/john_gass
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Malcolm_Stewart
Carpal \'Tunnel
Reged: 11/07/2005
Posts: 2583
Loc: Milton Keynes, UK
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I guess that's probably because their printer is expecting a "spooled print" file. Commercially, it's probably advantageous for them as it puts the technical and artistic burden on the photographer.
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Malcolm Stewart
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Paul_R
Pooh-Bah
Reged: 16/06/2006
Posts: 1968
Loc: Middlesbrough, England.
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Thanks again guys for your feedback. So, maybe, it looks like it really isn't necessary to resize images prior to printing. PS seems to incresae the ppi anyway to around 240.
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Regards, Paul CRIPN
http://www.pbase.com/exposethelight
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LargeFormat
old hand
Reged: 24/10/2006
Posts: 1184
Loc: Buckinghamshire and Cumbria
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Quote:
Thanks again guys for your feedback. So, maybe, it looks like it really isn't necessary to resize images prior to printing. PS seems to incresae the ppi anyway to around 240.
I don't quite agree with this. If you are printing at 300dpi from the file as produced by the camera you can print without worrying about resizing. For example an unsized 8MP file will print an 8 x 6 with pixels to spare at 300dpi. If you wanted to print the same file to, say, A3 it might pay to upscale to avoid jaggies on the finished print. Of course you will get no more detail as the extra pixels are merely interpolated from those produced by the camera.
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Malcolm_Stewart
Carpal \'Tunnel
Reged: 11/07/2005
Posts: 2583
Loc: Milton Keynes, UK
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Quote:
... If you wanted to print the same file to, say, A3 it might pay to upscale to avoid jaggies on the finished print. Of course you will get no more detail as the extra pixels are merely interpolated from those produced by the camera.
Printed as described above, I've never seen jaggies on my A3+ prints on Premium Gloss Paper (Epson) or highly glazed glossy film (Pictorico). I've printed to A3+ from 6MP EOS 10D and 12.8MP EOS 5D files.
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Malcolm Stewart
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sofinetti
journeyman
Reged: 06/03/2006
Posts: 57
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Maybe I'm a bit offtopic but I've noticed something similar, if I print 10x15 cm to 15x21cm the genuine file size out from the camera -Canon 30D- to my local minilab the pictures look softer than downsized around 1500 pix on the longest side.(accidentaly noticed).
I wonder why.
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LargeFormat
old hand
Reged: 24/10/2006
Posts: 1184
Loc: Buckinghamshire and Cumbria
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Quote:
Printed as described above, I've never seen jaggies on my A3+ prints on Premium Gloss Paper (Epson) or highly glazed glossy film (Pictorico). I've printed to A3+ from 6MP EOS 10D and 12.8MP EOS 5D files.
I did say MIGHT. I have seen jaggies.
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Monobod
'Phantom' of the forum!
Reged: 03/04/2003
Posts: 5992
Loc: Just West of Norwich, Norfolk
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I turn off 'Resample' to prevent interpolation and change the image dimension to fit the paper. The 'dots per inch' changes automatically. Providing this is not less than about 240 dpi I can get a high quality print. As most printers can deal with 1440 dpi, there is no problem with higher numbers such as 360 dpi for example.
It has been said that using a multiple of the printer resolution gives maximum quality. 1440/2 = 720 720/2 = 360dpi giving 4 droplets per pixel. Then the printer driver does not have to make adjustments of its own to the pixel map. Printers that claim to use 'variable droplet size' often only actually have two sizes, so the printer cannot always adjust the droplets to exactly match 240 or 300 dpi. Depending on the viewing distance of the print by the observer, this hardly matters in reality. You can view a print at 360 dpi closer than one at 180 dpi, but at the correct distance for the resolution there will be little observable difference. Think of a newspaper image built from dots. Seen close it is just that, but at normal distance it is a photo. 
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David.
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Photos hosted by Flickr.
www.flickr.com/photos/monobod/
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I see the world thro' a viewfinder, but the world watches me via CCTV!
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beejaybee
Marvin
Reged: 18/07/2007
Posts: 4980
Loc: Really Here In Name Only
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Quote:
I turn off 'Resample' to prevent interpolation
Why? I would have thought preventing resampling would be a good way of ensuring that the image quality was degraded.
Only when reducing to an integral fraction of the original size (1/2, 1/3, 1/4 etc) is resampling not worth while, even then it does no harm apart from consuming a few CPU cycles.
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LargeFormat
old hand
Reged: 24/10/2006
Posts: 1184
Loc: Buckinghamshire and Cumbria
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You can argue that 240dpi is enough or 300dpi is too much if you like but the printer output has nothing to do with it. Try clipping out a small piece of a photograph and printing, say, an 8x6 at 2800dpi printer resolution. The resolution of the print will be that of the original file not that of the printer although the printer will tend to blur the individual pixels.
Resolution is also nothing to do with the viewing distance. The adage is that one is comfortable viewing a large print at a greater distance than a smaller print. People view, say, 8x6 prints at the same distance whatever the resolution.
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Monobod
'Phantom' of the forum!
Reged: 03/04/2003
Posts: 5992
Loc: Just West of Norwich, Norfolk
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Quote:
Resolution is also nothing to do with the viewing distance. The adage is that one is comfortable viewing a large print at a greater distance than a smaller print. People view, say, 8x6 prints at the same distance whatever the resolution.
This is simply not the case. If I constructed an image out of pixels one inch (25mm) square (ie 1 ppi) and you looked at it from 3 feet away, it would look like a collection of coloured squares, but seen from 100 metres away, it would look like a photograph....obvious surely?
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David.
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Photos hosted by Flickr.
www.flickr.com/photos/monobod/
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I see the world thro' a viewfinder, but the world watches me via CCTV!
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LargeFormat
old hand
Reged: 24/10/2006
Posts: 1184
Loc: Buckinghamshire and Cumbria
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If I had a 6 x 4 made up of one inch squares (ie 24 squares in total) and I had a 6 x 4 made up of, say, 2.4MP (ie 1/1,000 inch square) I would look at them both from about two feet. I would not look at the first one from 100 metres away as you suggest. Indeed, I doubt that I could make anything out at that distance.
If the picture with the one inch square pixels had the same number of pixels as the 2.4MP picture the size would be something like 500 feet by 333 feet and the corresponding viewing distance would be about a kilometre.
What you are actually saying is that the picture made from larger pixels needs to be much larger than one made from smaller pixels to have the same resolution and for the pixels to look the same it needs to be viewed from further away. This is the basis for the standard advice that one can drop below 300dpi on larger prints because they will be viewed from further away.
Ergo it is the size of the picture that determines the comfortable viewing distance.
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Monobod
'Phantom' of the forum!
Reged: 03/04/2003
Posts: 5992
Loc: Just West of Norwich, Norfolk
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Exactly. But resolution must have a part to play if the detail is to be preserved in a print of the same size. My distances and pixel sizes were not meant to be accurate samples, just an illustration, you understand.
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David.
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Photos hosted by Flickr.
www.flickr.com/photos/monobod/
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I see the world thro' a viewfinder, but the world watches me via CCTV!
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