Megapixel and print size

Started May 10, 2012 | Discussions
Vipergfx
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Megapixel and print size
May 10, 2012

Hi All,
Im Just looking for a litle clarification.

Can I do any large format (24"+) with my 18mp camera or will it all come out like crap?

Im not looking to blow up portraits but more like landscapes and buildings.

Any advice is welcome on how that all works.

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Canon 60D, Can 50mm 1.4, Can 17-55 2.8, Can 10-22mm 3.5-4.5, 430 speedlite flash.

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rpenmanparker
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Re: Megapixel and print size
In reply to Vipergfx, May 10, 2012

I don't have the personal experience yet, but folks claim very high blow ups when using Qimage and possibly other popular editing software like PS and PSP. There are two choices: 1) You can print the large photo with the image pixel count as is coming out of the camera with any cropping you need to do, even if that means the linear ppi (pixels per inch) will drop below the preferred 300 at the size you want. Much below 200 ppi you would expect to see significant image degradation. Or 2) you can resize the image to the size you want, specifying 300 ppi or so and let the softwae (PS, PPS, Qimage, etc.) use a complicated algorithm to create the missing pixels by interpolation assuiming we are talking about a size large enough that your 18 original megapixels doesn't cover your desired size at the 300 ppi X 300 ppi density. Of course, the software can't fabricate pixels ad infinitum. There is a practical limit which you can discover for yourself when you examine your prints for the quality attributes you want. The latter approach is by far the preferred way. There has been plenty written about this here.

So if you keep all 18 mega pixels your image starts with the square root of (18,000,000/1.5) on the short side assuming 1 X 1.5 aspect ratio sensor. 1.5 times that for the long side. That is 3,464 pixels on the short side and 5,196 pixel on the long side. With no cropping, let's divide each of these by 300 per inch to give 11.5 X 17.3. Thatis how big your print could be at the preferred pixel density using all the natural pixels. If you want bigger, you will have to create new pixels using the software. The process is called resizing. Based on published recommendations, 17 X 26 inches should be no sweat. Based on what folks say in this forum, you can go significantly larger.

I hope this helps.

Robert

Lots of folks will chime in to this discussion and I'm sure give you a lot more help. This is just the overview.

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Phil Hill
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Re: Megapixel and print size
In reply to Vipergfx, May 10, 2012

Vipergfx wrote:

Can I do any large format (24"+) with my 18mp camera or will it all come out like crap?

In terms of MP, 18 MP is plenty for a 24-inch print. However, the quality of the image and how you prepare it for printing are just as important.

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Hugowolf
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Re: Megapixel and print size
In reply to Vipergfx, May 10, 2012

Vipergfx wrote:

Can I do any large format (24"+) with my 18mp camera or will it all come out like crap?

It really depends not only one the pixel dimensions, but also the quality of the image and expected viewing distance from the image.

Higher ISO will not work, any camera shake will be exaggerated, misfocusing will be obvious, etc.

I have plenty of prints from a 5D (12.something Mp) that worked fine at 24 x 36 inches. I have a few images from the original Canon 300D that are fine at 17 x 25.5 inches, and I have 21 Mp images that would be better on 4 x 6 inch paper.

One of the things about uprezing in Photoshop is that it allows you to view the image at 100% so that you have some idea if it will work at that rez. Programs like Lightroom don’t do that, but generally with experience you have a good idea what will work and what will not. With a high quality fine art paper, you could be looking at $15 worth of paper and ink at 24 x 36 inches – misprints and full sized proofs are worth avoiding.

Brain A

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Petruska
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This works very well
In reply to Vipergfx, May 10, 2012
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rpenmanparker
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Re: Megapixel and print size
In reply to Hugowolf, May 10, 2012

Yes, the cost of experimenting could be quite high, but even if you want to hard proof, it is not necessary to print the whole image to see whether a certain level of enlargement will work. Once a person really gets to understand the math (sorry guys, I know lots of you don't like to think about that) or you have good working relationship with your printing software (Qimage, for example) there is no reason you can't just crop out a 4 X 6 section of a really large image and print that at the same pixel size and density. That way you are only risking maybe $0.50 worth of fine art paper and ink. If the cropped section (say the eyes and a little hair in a portrait) look good, then printing the entire image on the full size paper is a much lower risk exercise.

Robert

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Hugowolf
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Re: Megapixel and print size
In reply to rpenmanparker, May 10, 2012

rpenmanparker wrote:

Yes, the cost of experimenting could be quite high, but even if you want to hard proof, it is not necessary to print the whole image to see whether a certain level of enlargement will work.

It is sometimes necessary, but not based solely on resolution. You might want to look at Keith Cooper’s recent thread on his 14 m pano – when you get big, it can be difficult to imagine how the results will play.

Once a person really gets to understand the math (sorry guys, I know lots of you don't like to think about that) or you have good working relationship with your printing software (Qimage, for example) there is no reason you can't just crop out a 4 X 6 section of a really large image and print that at the same pixel size and density.

I don’t know of many 24 inch or larger printers that will print as small as 4 x 6 inches, 8 inch rolls are usually a minimum (often actually 10 inch rolls) and 8.5 x 11 or A4 for sheets.

Robert, have you a good working relationship with QImage?

Brian A

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GMack
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Re: Megapixel and print size
In reply to rpenmanparker, May 10, 2012

Robert has it right.

Here's a site that shows you the "Megapixels and Print Size" chart:

http://www.design215.com/toolbox/megapixels.php

You'll see it more in fine detail areas like grass, leaves, branches etc. when you push the limits and they get "blocky" or jagged. Large items are of less consequence and can be up-rezzed or toss in some generated pixels in software.

Depends on your tolerance level too.

Mack

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rpenmanparker
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Re: Megapixel and print size
In reply to Hugowolf, May 10, 2012

Hugowolf wrote:

rpenmanparker wrote:

Yes, the cost of experimenting could be quite high, but even if you want to hard proof, it is not necessary to print the whole image to see whether a certain level of enlargement will work.

It is sometimes necessary, but not based solely on resolution. You might want to look at Keith Cooper’s recent thread on his 14 m pano – when you get big, it can be difficult to imagine how the results will play.

Once a person really gets to understand the math (sorry guys, I know lots of you don't like to think about that) or you have good working relationship with your printing software (Qimage, for example) there is no reason you can't just crop out a 4 X 6 section of a really large image and print that at the same pixel size and density.

I don’t know of many 24 inch or larger printers that will print as small as 4 x 6 inches, 8 inch rolls are usually a minimum (often actually 10 inch rolls) and 8.5 x 11 or A4 for sheets.

Robert, have you a good working relationship with QImage?

Brian A

Thanks for the comments, Brian. I wasn't really thinking about the large format printers so I likely was off base regarding 4X6. But even an 8X10 which I suppose could be created from an 8" paper roll would represent a big savings over a 24X36, less than 1/10th in fact. So there is merit to the idea of hard proofing with a much smaller size to conserve materials.

On the QImage question, there you've got me. I just bought it and installed it, but my first look is not encouraging. So far everything I want to do (limited I admit) looks more easiily and intuitively done in my Paint Shop Pro X4. So the answer is no, I really don't have a good relationship (yet) with QImage. My mention of it was a tip of the cap to its many avid users who say such good things about it on this forum. With my background I am really more of the hands on math type. My message was that whichever approach you take the one I prefer or the one so loved by many others, there is a way to creat a cropped section of the full image to print on smaller media. Different strokes for different folks.

Robert

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Hugowolf
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Re: Megapixel and print size
In reply to rpenmanparker, May 10, 2012

rpenmanparker wrote:

Hugowolf wrote:

rpenmanparker wrote:

Thanks for the comments, Brian. I wasn't really thinking about the large format printers so I likely was off base regarding 4X6. But even an 8X10 which I suppose could be created from an 8" paper roll would represent a big savings over a 24X36, less than 1/10th in fact. So there is merit to the idea of hard proofing with a much smaller size to conserve materials.

My MO, when I wasn’t certain of how an image would work with a specific paper and/or resolution, was to print an A4/US letter sized sheet, one half with the whole image, the other half with a 100% crop. Nowadays I only use this to convince others that their P&S image isn’t going to work at 24 by 36 inches.

On the QImage question, there you've got me. I just bought it and installed it, but my first look is not encouraging. So far everything I want to do (limited I admit) looks more easiily and intuitively done in my Paint Shop Pro X4. So the answer is no, I really don't have a good relationship (yet) with QImage.

I have been trying to avoid using QImage since I started using Lightroom. It has a horrible UI and adds an extra step to the workflow. Every time I open up QImage, I cringe. Lightroom does almost all that I want, now that version 4 has softproofing, but still doesn’t have scaling, so 100% crops have to be approximated. It does a remarkably good job of automatically uprezing to the input screening resolution (360 ppi for Epson and 300 ppi for Canon and HP), but it is an internal operation and you don’t get to see it.

Brian A

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