Friday, January 11, 2013

Making a Monster Print

I recently had a tough challenge:  I needed to produce a panoramic image that was 7 meters wide by 2.5 meters tall.  In the American measurement system, the image would be 260 inches, or 21 feet and 8 inches long.  The height of the image would be 106 inches, or 8 feet and 10 inches tall.  I failed to make that goal with my initial attempt, which resulted in a 24x7 foot image.  However, I did produce an 11x5.5 foot image with 225 ppi (pixels per inch), and in the process learned a fair amount about producing large format prints, or monster prints.

I don’t know exactly what the lower limit of a large format, or monster print, would be.  I once produced a terrific 20x30 image from a 6 megapixel camera.  That would certainly be considered a monster print for that camera.

So let’s just say that anything over a 30x40 in size taken with a 12 megapixel sensor qualifies as a monster print.  That’s arbitrary, but you have to start somewhere.
The important things to remember is that you only have so many pixels, or film grains if you prefer, in your image file, and they must somehow be stretched to fill the monster space. One way to accomplish that is to produce a straightforward enlargement, in which the pixels get spaced further and further apart.  Imagine putting some stick-on stars on a balloon and blowing it up.  At it gets bigger, the stars get bigger, but so do the spaces between them.
 
As an extreme example, you can print a tail wrap for a jet aircraft at 25 ppi.  At a hundred yards or more in distance, no one will notice that the image is a little soft.  In fact, at that distance, it looks tack sharp.  Just for an example, an 8x10 at 300 ppi equals 120x96 at 25 ppi.

The pictures below won’t look right because of the limitations of the web.  However, you can see that the overall view at 300 ppi is sharper than the close-up view at 25 ppi. It wouldn’t be the case if the 25 ppi were 15 feet away!  You can test this by getting out of your chair and moving back a few feet.  Both images look very crisp at a bit over 7 feet.

Flowers at 300 ppi, by Eric Hatch

Flowers at 25 ppi, by Eric Hatch
Step one in making a monster print is figuring out how far away the image will be seen.  For magazines and most prints, 300 ppi is a good, tight resolution.  If you’re going to be looking at the image from one to three feet away, you definitely need a 300 ppi resolution or higher.  However, if you’re looking at the image from 20 feet away, 220 ppi is acceptable.  In some instances, even 180 ppi would be sufficient.

If you simply enlarge an image, treating all parts equally, the edges of the pixels themselves get fuzzy and the space between them gets larger. So, dealing with the distance between pixels is a major part of making monster prints. Almost all image handling programs have routines that allow the computer to generate new pixels that it thinks would look good between two current ones.  This is called “uprezzing” or “rezzing up” - increasing the effective resolution to fill in the vacant spaces between the stars.

Taking your best image and “rezzing” it up is another approach to producing monster prints.  If you start with a monster file, you can make a monster print. However, eventually this technique fails.  It fails because the more the computer has to guess and interpolate data to fill in the spaces, the fuzzier and less accurate the whole image becomes. 

Simple enlarging won’t yield monster prints at reasonably high resolution from normal file sizes.  Rezzing up reaches a limit, and may end up creating an undesirable image.  So what else can you do?

One thing you can do is take a number of overlapping shots, and stitch them together with appropriate software. Then, you can enlarge the result to the specified size.  In my opinion, stitching is the better way to go.

However, to get the best results you have to take some precautions.  First, though this is obvious, use a moderate telephoto lens to limit your field of view, thus increasing the number of exposures you can take.  I say moderate because you don’t want to induce distortion, especially where the edges will be stitched.  Also, any vibration or motion blur will be fatal to your image.  The more you magnify the image, the more any form of motion is exaggerated.   This is why super zooms are not recommended. I use a 100mm prime for this job.   A 60mm lens would work just as well.

Lens quality is another essential for making monster prints.  Any flaws or aberrations will be obvious at monster sizes where they might not even be noticeable on an 8x10 image. My advice is to use good glass.

Panoramic Image of Bridge, by Eric Hatch
As an example, the above image is what I started with.  It was originally a 24x7 inch panoramic imaged stitched from 6 shots.

Bridge Close Up, by Eric Hatch

At 160 inches wide and 225 ppi, here’s what an excerpt looks like at printing size.  Doesn’t look great, but if you back away from your computer about 5 or 6 feet it looks okay.

Here's a curve ball:  Photoshop and many other image manipulation programs have a 30,000 pixel size limit for JPEG images.  They just won't operate reliably past that size.  You'll need to work in Large Image Format or TIFF files to produce monster prints.  The downside is it will drain your computer power.

You can get around the size limit by enlarging your stitched image using something like Perfect Resize from OnOne software. In dealing with my tough challenge of producing a large panoramic image, I "cheated" the program by enlarging my image to the limit, then removing 1/2 of the resulting image and pasting it into a new blank image.  Next, I enlarged that image to the maximum.  I did the same with the other half, and then pasted both up-sized images into a new blank image. In this case it was sized to twice the limit.

The end result was a 4 gig file, so be prepared to kill some time while it's processing.  The process was complicated, but it worked.  However, even the best program run into problems at monstrous sizes.  You can't keep repeating the steps because the image gets too blurry.

With a Nikon D800 DSLR or a Mamiya Leaf medium format camera, you shouldn't encounter any problems because the native file sizes are so large.  I would shoot the image in 12 bit color, which saves you some file size, again at some cost in depth and beauty.

The D800 produces an image approximately 16x24 in size at 300ppi.  You'll need 12 images across and 8 down (allowing for overlap) to produce a 6x3 meter print without uprezzing.   Even at 300ppi, the final image will be sharp, sharp, sharp.  You can get by with proportionately fewer images if, as suggested above, you drop the ppi density to 225 or so.  Again, talk to your client and to their art production house as to how they want to use the final image.

The sample image below started life as four, 12 megapixel raw files.  They were stitched vertically to produce a 19x24 inch image.  This in turn was rezzed up in PerfectResize to yield a 50x75 inch picture.  This was well into monster print territory and nowhere near its limit.  This image isn’t perfect; there are a few soft focus areas, but overall it conveys the sense of vertical depth I was after.

Thunderbird Falls, by Eric Hatch
It’s mildly frustrating because there’s no way to display monster prints on an internet site!


Contributor Bio:
Eric K. Hatch focuses on travel and fine art photography, and is an expert in digital photo restoration. Panoramas are currently one of his favorite photographic forms. He has won numerous regional awards and a number of competitions. His work has appeared in several AAA magazines, Oxygen Magazine, Bicycling, Alaska Milepost (annual) and Wooden Boat, to name a few. He has served on the board of the Southwest Ohio Professional Photographers Association, an affiliate of the Professional Photographers of America.

Eric has also written over 70 articles, essays, speeches, features, and professional articles in the last 30 years. His work has won two national awards: a Gold Quill from the International Association of Business Communicators, and Communicator of the Year from the Aviation/Space Writers Association.

In his youth, Eric studied under Guido Organschi, and later under Skip Schiel. He is the author of Explorations in Photography, Adventures and Advice for Advanced Amateur Photographers, which was recently released.


Explorations in Photography is an entertaining and informative how-to for advanced amateur photographers. The book covers artistic issues, explains some fundamental technical issues, and provides many hints from buying equipment to editing your photos. It also covers taking people pictures outdoors, handling nasty lighting situations, and includes a bonus chapter discussing photo restoration. Find it on Amazon.

Websites:
General Portfolio: http://ekhphoto.smugmug.com
Blog: http://hatchphotoartistry.blogspot.com
Photo Restoration: http://www.hatchphotofix.com

* Readers can also get a fresh photo tip of the day several times a week at my website Explorations in Photography

2 comments:

  1. Regarding your comment: "It’s mildly frustrating because there’s no way to display monster prints on an internet site!", I've been using a great service zoom.it that lets people view huge images with super-smooth zooming ability. I'm not affiliated with them, just a happy customer. Here's a sample I created by stitching a lot of mars photos:
    http://zoom.it/f4kS

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  2. There's also the excellent gigapan.com where owners of motorized Gigapan equipment post online versions of massive gigapixel images. I recently printed a 236 megapixel image (37103 x 6362 pixels) as 36-foot-wide wall mural that completely wrapped two walls. We had enough original resolution to print at 100 dpi, but we decided to upres by 50% so we could increase the height from 60 inches up to 96 inches high. When you have that much detail, it's an incredible immersive experience.

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