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DannyH
6th July 2009, 03:39 PM
I just started printing up some of my photo's in CS3 and noticed in "Image size" that with "large fine" and "Large super fine" the dimensions are

Width 3648 pixels/11.6 inches
Height 2736 pixels/8.7 inches
Resolution = 314

In Tiff of JPG converted from RAW

Width 3643 pixels 15.2 inches
Height 2736 pixels/11.4 inches
Resolution = 240

My question: Is it normal to have a size of 8.7" x 11.6" for the standard JPG mode, and does this affect me trying to print a 13x19 size? I have a small point and shoot, and those photo's come up with 26"x35", but only 80 resolution. If printing a larger print, does it make any difference to increase the size in image size?

I'm slowly trying out RAW, and I'm wondering if thatís best if I want larger prints. It may be that I have my settings incorrect, but these are what seem to be the standard thatís coming up.

Thanks

Wreckdiver
6th July 2009, 04:43 PM
As a guide, if you are printing high quality, say for a glossy magazine, then you should aim for 240 to 300 ppi (pixels per inch). At the other end of the scale (web use for display on a monitor) you would use around 70 to 90 ppi. Other uses somewhere in between depending on quality you require.

So if you want a 11" x 9" print at top quality (300 ppi) then you need an image size of 11 x 300 by 9 x 300 which is 3300px by 2700px.

Always start with the ppi density you require (i.e. quality) then multiply by the output size (in inches) you want to get the required image size (in pixels) to start with.

Hope that helps,

Steve

DannyH
6th July 2009, 11:40 PM
Thanks for the reply Steve. That what I needed.

OlyPaul
7th July 2009, 12:54 PM
Danny digital images only have a pixel dimension and do not have a size untill you output them. So what ppi is shown does not matter and you can change it to suit the output device , of course the more ppi the smaller your outputed image will be unless you intropolate the image (make up pixals that were never captured).

As to what is normal..well there is no normal, for instance your 314ppi from camera native jpegs is because the Olympus Dye printer has a native output of 314ppi. The reason your raw converted image is 240ppi is because it is considered the standard resolution for ink jet printing by Adobe, its just a arbitary number assigned by the software manafacturer.

The reason some consider 300ppi the norm is because it was what was used for offset printing but even that has changed now.

The only printer I know of now that uses a native 300ppi is the Fuji frontier lab printer which prints up to 15x12 and the large format printer has a native res of 260ppi .

So once again there is no such thing as ppi (only pixel dimensions) untill it is outputed as a printed image. If there was then a web image of 800 x 600px at 300ppi would not display the same size as a 800 x 600px at 72ppi and they do.:)

Wreckdiver
7th July 2009, 02:53 PM
Just to clarify, a printer accepts the output from photoshop in ppi (and hence determining final print size) and outputs to paper in dpi. The printer software converts ppi to dpi. The dpi printer output numbers are much greater than the ppi values (typically 1440, 2880 etc.). The relationship between ppi and dpi lies with the printer manufacture and printer drivers.

Steve

Adagio
8th July 2009, 10:56 AM
Just to clarify, a printer accepts the output from photoshop in ppi (and hence determining final print size) and outputs to paper in dpi.

I am not sure that I fully understand this. My native dimensions RAW-->DNG-->PS gives image size of 38.61x28.96 cm 240 ppi. If I attempt to print these are the dimensions of the printed image (on A4 the width is cropped if I do not scale to fit).

Change image size to 10x7.5 cm (no resampling) 926.592 ppi it will print 10x7 cm

I believe that the printer driver will convert the input ppi to its required dpi for the defined print size.

Wreckdiver
8th July 2009, 11:29 AM
Firstly, you are mixing metric and imperial units. So let's convert everything to imperial.

38.61cm by 28.96cm is 15.2" by 11.4". The density is 240 ppi so the size of the image is 15.2 x 240 by 11.4 x 240 which is 3648 px by 2736 px (10Mp camera) so this will not fit on an A4 sheet when printed full size, hence your picture is cropped as you say.

When you reduce (without resampling) to 10 by 7.5cm (3.937" by 2.953") the density goes up to the 926.592 ppi because you need to "squeeze" the same amount of pixels into a smaller space. If we do the maths we get 3.937 x 926.592 by 2.953 x 926.592 which again is 3648 by 2736, which is what it should be. This will print at 10 by 7.5cm (3.937" by 2.953") when printed full size on an A4 sheet.

You don't need to worry too much about dpi or what the printer will do. As long as you set up PS to send your image to the printer at the required ppi density and physical size the printer and it's drivers will sort everything out.

Does this answer your questions?

Steve

Wreckdiver
8th July 2009, 11:41 AM
Just to add to the final sentence above. Whatever the print quality you set your printer to print at you will always get a 3.937" by 2.953" picture. At low quality the printer will disregard many of the pixels you send it, at high quality more of the pixels will be used. As you are printing at a huge 926 ppi the image quality will be far higher then the human eye can ever detect. The generally accepted limit of the human eye is around the 300 ppi value when viewing a 10" x 8" image at a specific distance (I can't remember exactly what this is), but suffice to say, you can reduce the ppi value when the viewing distance increases to get an apparant similar quality.


Steve

Adagio
8th July 2009, 12:01 PM
What confused me was that in this post Above you make no mention of physical dimension. I misinterpreted this to mean that you believed that the physical size setting was immaterial. Sorry for the misunderstanding. I think that in
I believe that the printer driver will convert the input ppi to its required dpi for the defined print size.
we are both saying the same thing.

Wreckdiver
8th July 2009, 12:13 PM
All you need to worry about is setting the desired output physical size at the required ppi and then send it to the printer. Set the printer's print quality to whatever quality you want (draft to photo quality), choose an appropriate paper to match the quality and you will get the size of print you wanted.

Steve