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Old Jul 13, 2006, 10:50 AM   #11
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How big? It mostly depends on the image. For example, a detailed landscape with foliage, grass, mountains, clouds, animals, trees, etc would require alot of detail and require a lot of dpi or ppi. A less detailed image such as a flower close up and be blown up much larger before the apparent lose of detail becomes obvious.

Processing also has alot to do with percieved image quality too.

As a general rule of thumb though the limits you could push an average (agian this is subjective) photograph would be about 150-180ppi. I would not suggest going below 150.

Here is a calculator tool that will give you many popular print sizes and the PPI number that correclates to them for a given camera: http://www.mattspinelli.com/ppicalc.html

For you camera here is the 150ppi limit I would suggest:

12 x 16 = 162 ppi
12 x 18 = 144 ppi

So 12x18 would probalby be pushing it too much. Thus, 12x16 may be the largest you could go.

At 162ppi, the minimum viewing distance is about 2 feet.

I don't know where I did research on this but the numbers are similar to the3500/inches figues Sintares quoted, but here I thefigures forminimum viewing distance:

100 ppi = 34 inches
150 ppi = 23 inches
200 ppi = 17 inches
250 ppi = 14 inches
300 ppi =11.5 inches

I would say these are guidelines and are for average viewing. For critical viewing I would double these PPI values to:


100 ppi = 68 inches
150 pp = 45 inches
200 ppi = 34 inches
250 ppi = 28 inches
300ppi = 23 inches


Again these viewing distance charts are subjective. If ever someone wants to look at the image up close youWILL haveproblems if it is printed below 150 ppi IMO.

My advice isto see how the image looks at arms length. If it looks blury or pixelated then it's not good enough.











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Old Jul 13, 2006, 3:53 PM   #12
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nelmr wrote:
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How big? It mostly depends on the image. For example, a detailed landscape with foliage, grass, mountains, clouds, animals, trees, etc would require alot of detail and require a lot of dpi or ppi.
Your post completely leaves out the question of interpolation and its effects on an image. Glancing at one of my 16x20 images, aquired from a five meg camera, I see that I have a PPI of 300. This of course was from interpolating (up-sampling) it up to get this ppi.

Is interpolation as good as having captured the image originally at such a ppi? No. But I doubt if the viewer, staring at a foot away could tell the difference.

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Old Jul 13, 2006, 3:56 PM   #13
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So this interpolating thing you're all talking about, could I do that with Photoshop Elements 4? I have a trial version of that and can purchase the real version if necessary. Photoshop CS2 is out of the question however.
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Old Jul 13, 2006, 4:44 PM   #14
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Yes, don't have PSE, but I think it would be

Image - resize - image size ?

There should be a Resample Image box you can select , then choose Bicubic for the interpolation method.

Tick the constrain proportions box (to keep the same proportions) then enter new values for width or height and ok.

When ok is clicked the photo will be up or down sampled depending on if you entered a larger or smaller size when changing the width/height.

The ticked resample box, forces the software to add or subtract pixels using the preselected bicubic method which I think is the best method PSE has.

Some people say the best results are done by resampling 10% at a time eg if you wanted to double the size of your 2592 x 1944 image , they say don't just do the resample to 5184 x 3888 in one go, but resample to 2851 x 2138 (10%) then again another 10% etc till you reach the desired size.

Whether that produces a better image or is just a waste of time ... umm don't know.
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Old Jul 14, 2006, 12:11 AM   #15
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So if I upsize my image until I reach the desired size at 300ppi, it will theoretically look better than if I just used a lower number of pixels per inch?
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Old Jul 14, 2006, 12:35 AM   #16
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I use both Genuine Fractals and stepped interpolation (SI) with 5% increments. For most images the SI upsample is slightly better than GF. Both methods are better than any straight upsample I have found. 10% increments are almost as good and a better choice for computers without gobs of RAM. I have seen sites where people recommended 2% increments, but I tried it and couldn't see any improvement over 5%. And it takes forever.

Some people like Bicubic Smoother in Photoshop but I find it a little soft. Luminous Landscape had a recommendation for making it 120% of what you need with Bicubic Smoother and reducing back the 20% with Bicubic Sharper. That doesn't do anything for me either.

The freeware Irfanview with its Lanczos resample filter is as good as any straight resample in Photoshop IMO.

No upsample regardless of sophistication really does much. If the detail isn't there it will show in the print. If the resolution is really low it makes the print look a little smoother.

I don't think there is a formula that will tell you exactly how large a print you can make from 5Mp. I have 13 X 17 prints on my wall from 5Mp images that look quite good. But different subject matter seems to require different resolutions. The picture I think requires the best resolution is a group shot of people. Viewers seem to put their noses almost against the print to see the individual faces and low resolution is very apparent. A landscape or sunset can look very good at lower resolution.

I think this would probably be the cheapest way to get a top notch image editor: http://cgi.ebay.com/Corel-Paint-Shop...QQcmdZViewItem It is the full version of Paint Shop Pro X that can be registered and has no restrictions. Corel released this version to be sold with new equipment, so they send you a useless piece of junk to make the transaction legal. It is an overall more competent program than Elements IMO.

The resample in Photoshop is accessed with Image > Image Size. I think Elements is the same.


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Old Jul 14, 2006, 8:03 AM   #17
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DBB wrote:
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nelmr wrote:
Quote:
How big? It mostly depends on the image. For example, a detailed landscape with foliage, grass, mountains, clouds, animals, trees, etc would require alot of detail and require a lot of dpi or ppi.
Your post completely leaves out the question of interpolation and its effects on an image. Glancing at one of my 16x20 images, aquired from a five meg camera, I see that I have a PPI of 300. This of course was from interpolating (up-sampling) it up to get this ppi.

Is interpolation as good as having captured the image originally at such a ppi? No. But I doubt if the viewer, staring at a foot away could tell the difference.

Dave
DBB,

When I talk about neede PPI I am refering to the native PPI of the camera for a given print size. When It comes to interpolated PPI that depends on the printer (240 vs. 300 vs ??? PPI).

Interpolation is only going to do so much. IF you have an image of a landscape with foliage that is quite a ways a way there won't be detail in it if the camera doesn't resolve it. No amount of interpolating will retrive it. Thus the only real alternative we have for sharp prints at arms length is to make sure the PPI value is high enough that we don't see the area of non-detail (blotchy, bluring, inconclusive look).

It does depend on the image. If the majority of the subject is in the DOF and is detailed and sharp then it may blow up big. However, with landscapes that normally have the goal of hyperfocal focus to have as big a DOF as possible, blowing it up to the point the PPI drops below 150 in most cases will produce an unstatisfactory print in my opinon due to the lack of microdetail. I am not saying that every image needs at least 150, what I am saying is that the most demanding images would make 150 pushing it. Some images need to be up'd to 180 for arms length prints.

I generally interpolate all my images before printing to smoth out jaggies. GF, SI, and other interpolation won't do a lot to help out here. BTW, I've tried SI at 5% and 10% and have not been able to produce results better than single step bicubic. To me SI doesn't improve. GF will help if the image has a lot of hard lines but it doesn't add detail. That is what my point is. Without detail to begin with interpolating won't do much.

Now, my standards may not be the same as everyone else. I know a friend that printed a 96dpi 24x36 print from an 8 mp camera and is quite happy with it. To me it looks blury and non-detailed. It's everyone's opinion I suppose.



"Is interpolation as good as having captured the image originally at such a ppi? No. But I doubt if the viewer, staring at a foot away could tell the difference."


The viewer, if unaware of what a 300 native ppi print looks like at 16x20 could be fooled. But if you had a 300 native ppi 16x20 print (29 megapixel camera) of the same subject next to the 121 native ppi 16x20 print (5 megapixel camera) I am sure that he could tell a difference at 1 foot. The resolution difference is 2.5x. Thats as big a difference as an 8x10 printed from an canon 350d verses a 1.3 megapixel camera.
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Old Jul 14, 2006, 10:55 AM   #18
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I have a question about resizing that may or may not have already been answered and I just did not understand. I use Elements 3 and a Canon D20.

When I crop out a picture to 8x10 and then check the PPi in the resize picture tab it was showing me only 139 ppi. According to what has been said in this forum, that would be to little ppi to print. So do I just goto the ppi and punch in 300 ppi and OK?

Will that make the print look right? Have I just cropped it out too small to make a good 8x10. What would I need to do to make this print work or will it. I have some that someday I want to blow up to poster size but I want to learn how to do this at a smaller cheaper size first.
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Old Jul 14, 2006, 12:24 PM   #19
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Quote:
"Is interpolation as good as having captured the image originally at such a ppi? No. But I doubt if the viewer, staring at a foot away could tell the difference."

The viewer, if unaware of what a 300 native ppi print looks like at 16x20 could be fooled. But if you had a 300 native ppi 16x20 print (29 megapixel camera) of the same subject next to the 121 native ppi 16x20 print (5 megapixel camera) I am sure that he could tell a difference at 1 foot. The resolution difference is 2.5x. Thats as big a difference as an 8x10 printed from an canon 350d verses a 1.3 megapixel camera.
Well first, didn't mean to scream at you...My bad!

If you wish to greatly enlarge an image, you have to have a SHARP image to begin with. I have 20,000 3x5's and they all look pretty good at that size. But a good proportion would look terrible blown up. These are film and not digital that I'm referring to here.

But a sharp image while it certainly doesn't gain by interpolation, doesn't degrade anywhere near as much as people think. And has been pointed out there are different approaches to interopolation.

These algorhytems essentially examine not just neighboring pixels (PS calls this method - "Nearest Neighbor"), but entire groups and areas of pixels and makes intelligent decisions about what to put inbetween these pixels in the process. So when we interpolate an image to four times it's original size we are not merely making one pixel and dividing it into four identical pixels, rather these intelligent algorhtyms "decide" that this pixel relates to twenty or thirty more, and that intermediate pixels of different colors have to be added.

Since I make a living printing out 16x20's I can glance at an image and tell if it will work or not.

So for example, THIS image is NOT suitable for 16 x 20



I like this image, but there is no detail. Blowing it up would look very soft. It would only work if the viewer was at a distance.

However - THIS image I could make 5 foot by 4 foot:



Note that even closer up even MORE detail becomes apparent.




There is a large amount off detail and the better interpolators, while they cannot add detail, can certainly keep the detail that is there. Certainly at 16x20 you would not be able to distinguish it from a photograph...

Dave
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Old Jul 14, 2006, 2:39 PM   #20
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DBB,

I think we are saying the same thing just in different ways. I am saying as a general rule 150ppi is the cutoff but yes, there may be some images that can be enlarged quite well. It's all about the detail and if there is enough of it to begin with.

I do however, still think a side by side comparision of a 150ppi or less print next to a 300 ppi print at 16x20 inches of t he same subject would have a noticable difference.

BTW, no hard feelings.
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