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Old Nov 9, 2003, 6:17 PM   #1
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Default largest print size from 2304 x 1712??

What is the largest good quality print I can have done of a 2304x1712 image from my 4mp Casio QV-R40? I am having it done at the local supermarket on their photo print thing there (I think they use the same print machine as for 35mm pics). I want it as large as possible to be framed as a present for someone. Advice please?
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Old Nov 9, 2003, 7:10 PM   #2
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Ralph:

That's a "loaded question" with no simple answer.

Everyone has a different opinion on what is acceptable.

What print sizes does the supermarket offer? If you're only talking about 8"x10" prints, then you should have no problem.

If you want 20x30 inch posters, then that's another matter entirely. You probably won't like the results.

Yes, you can do it (even with a 4 Megapixel Camera). However, it will require some preparation (interpolating the image to prevent pixelation), and the images may lack detail at closer viewing ranges, and look soft to some viewers. Subject matter also makes a big difference (portraits are great for larger sizes, but photos with lots of detail like landscapes with foilage are not real good candidates for poster size prints from a 4MP camera).

As far as print sizes, many will argue that 150 pixels per inch is plenty of resolution, with anything more a waste, since the human eye won't be able to tell the difference at normal viewing distances.

Others will argue that 200, or even 300 pixels per inch is necessary for the best quality.

Here's a chart that may help. You'll probably find that the "good" column is all you need (unless you're going to examine the print at very close range).

http://www.cordcamera.com/products/d...ct_ratios.html

Here's another chart that takes popular digital camera image sizes, and shows how many pixels per inch you'll be sending to the printer driver for popular print sizes:

http://home.earthlink.net/~terryleed...tables.htm#ppi
As I mentioned, you can interpolate an image using software. This does not increase the detail captured originally, but it does add pixels (based on the value of adjacent pixels). This lets you print larger images without pixelaton.

A good free package is irfanview. It has a very sophisticated Lanczos Filter based interpolation algorithm (you'll find this option under the resize/resample menu option). You can download the software (free) from this link:

http://www.irfanview.com

Here is an article discussing interpolation:

http://www.megapixel.net/html/articl...rpolation.html

I'd suggest going to at least 150ppi for your prints with most printers. With some printer types (dye sub), 300ppi is recommended for best results. Most of the larger commercial printers are using Fuji Frontier Equipment (which works well without a lot of prep on most images). But, if your local supermarket is using something different (like a small dye sub printer), then you may want to interpolate first if you are looking for a very large print size.

Then, you'll probably want to go to 300ppi using a package like irfanview (with the Lanczos Filter Option selected under the resize/resample menu). You can compute the number of pixels needed in the image easily (or just use one of the charts in the above links, before starting the interpolation process with software).

Interpolation will not add detail, but it will allow much larger print sizes without pixelation on more printer types.

Give us a better idea of the photos content (and what print sizes you're really looking for), and perhaps we can offer some better advise.

You may also want to read through this forum thread (discussing the same topic). Pay particular attention to the advise from Lin Evans (a long time pro digicam user, and an expert in this subject area):

http://www.stevesforums.com/phpBB2/v...?p=67915#67915
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Old Nov 9, 2003, 7:18 PM   #3
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thanks JimC - sorry, I did not realise it was such a loaded question. I will be going through all that info in detail in the morning.

The supermarket offers prints up to poster size (I cant remember how big, A3 or A2) - I dont want to waste 8 getting one copy printed at that size if its going to look terrible. It is a portrait taken indoors that I want to print. Not much background. I was hoping to just put my card into the machine and request a bigger copy (I usually go for 6x4) and get a good result - so lets say I do that - what would be a safe size - I would like around A3 if possible.
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Old Nov 9, 2003, 7:40 PM   #4
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Ralph:

I keep forgetting that in the UK, you use the "A" sizes (we use different "standard" print sizes in the U.S.)

You'd think that at this late stage, we could at least agree on standard print sizes. :lol:

That's going to be cutting it pretty close, without using any interpolation (depending on the way the printer handles the image).

Note the PPI being sent to the printer for an A3 size image from 4 and 5 Megapixel Cameras (between 135 and 155 ppi).

http://home.earthlink.net/~terryleed...tables.htm#ppi

I'll have to "break out a calculator, look up A3 in inches, and convert to see the actual PPI your model (at 2304 x 1712) -- also bearing in mind that it's not an "exact fit" to the print size (some cropping will occur at your aspect ratio of 4:3 from the digital camera).

Why don't you do this. E-mail me the photo (if you are comfortable doing this), and I'll be happy to interpolate it up to 300PPI (pixels per inch) for an A3 size print. Then I can e-mail it back to you.

This will insure that it's got enough pixels to prevent pixelation, regardless of the printer technology used.

Or, if you're comfortable using software, you can download irfanview.com and do it yourself. I'll take a few minutes and compute the pixels needed.

I'll send you my e-mail address via Private Messaging, and let you decide what is the best way to go.
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Old Nov 9, 2003, 8:00 PM   #5
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Ok

I have made the necessary calculations.

An A3 size print is 29.7 x 42.0 cm

This converts to 11.69 x 16.54 inches

So, in order to be safe (no unwanted pixelation, regardless of printer technology used), we'll want to take it to 300 pixels per inch.

300 x 11.69 inches = 3507
300 x 16.54 inches = 4962

So, for the ideal A3 size print (without any unwanted cropping), we'll want to crop ahead of time, interpolating the image so that we give the printer a 4962 x 3507 pixel file.

I got your photo. I'll work on it and e-mail it back.
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Old Nov 9, 2003, 8:27 PM   #6
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thanks a lot Jim, much appreciated.
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Old Nov 9, 2003, 9:35 PM   #7
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I will throw this out there. I have a Canon G3 camera (a 4 MP camera) and an i9100 photo printer (A3+ capable). I have gotten great prints, even up close from A3+ prints on my i9100 printer from my G3.

Some online photo finishers have their own standards for large poster prints. For example, Ofoto requires a minimum of 1600x1200 pixels (2 MP) for their 16x20 and 20x30-inch prints.
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Old Nov 10, 2003, 1:58 AM   #8
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When I had my 5700 (5MP) I made 20+ 13"x19" prints on my Canon S9000. The prints look sharp and extremely accurate with no visible pixelation/noise. Makes me wonder where the 'real' limit would be if my printer could accept larger photo paper. I have yet to make a 11x14 or 13x19 print from my new DX6490, I'm sure I'll let this forum know once I make a print that large...just for info sake
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Old Nov 10, 2003, 6:34 AM   #9
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In the case of most modern photo printers, I think the printer drivers are "rezzing up" the images to prevent pixelation, as they're being converted to dots per inch output for the printer.

I've read a lot about many dye subs needing at least 300 pixels per inch being sent to the printer drivers to prevent pixelation. Yet, 150ppi (or sometimes even less) looks fine on other printer types.

I think the Fuji Frontier setup being used by most larger printers is probably designed to prevent pixelation, too. My biggest concern was the "unknown" factor (since he'll be using a local supermarket, with unknown printer technology).

So, just to be safe, I figured it would be best to interpolate to 300ppi. I sent him back a 4962 x 3508 pixel file (pre-cropped for "A" type print sizes, to make sure the printer didn't crop it in a way that would be undesirable).

It looked "sharp as a tack" to begin with, and the interpolation looks fine (I actually tried several different software packages and methods, including using bicubic, in multiple steps up).

I ended up going back to using Lanczos (in the free irfanview software). It seemed to do just as well or better to my eyes, when magnified on screen, and I've had very good results with it at home, printing cropped 8x10's from an old Coolpix 950.

When finished, I took a cropped section from the interpolated image, and printed on my printer to make sure it would work OK (fine on my HP Photosmart 1215). Unfortunately, I don't have a bigger printer to work with (so I had to use a smaller section of the final image to test the interpolation results in print).

I'm going to have to "break down" and get me a Canon i9100 at some point.

I'm curious has to how well this will work at his local supermarket. This is now a 17.4 Megapixel Image (4962 x 3508).

This is 300 pixels per inch being sent to the printer driver for an A3 size print, more than 200ppi for an A2 size print, and still just over 150ppi for an A1 size print (if he wants to try it larger than A3).

Since it's a portrait, I think it will look fine at larger sizes, at typical viewing distances.
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Old Nov 10, 2003, 9:33 AM   #10
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Default Re: largest print size from 2304 x 1712??

Quote:
Originally Posted by ralphuk100
What is the largest good quality print I can have done of a 2304x1712 image
Crop out a small but important piece of the image in your image editor, print it at the right scaled-up size using your photo-quality inkjet printer, stick it on a wall and try viewing it from various distances. That'll soon give you an idea of the quality to expect.

I am agonising over the same problem at present, but with an 8967x1443 image of the City of Edinburgh.

When in doubt, do the experiment on a small scale first! The principle holds good for everything from chemistry to global conflict.
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