SuperFly48 Loc: NE ILLINOIS

I have read numerous thoughts/postings/articles on how large a print you can get from a particular size digital image file, this as it relates specifically to image sharpness and resolution. I was concerned a while back with determining how large a file I needed for a quality reproduction and this is how I have worked things out for myself. Please note, I spent over 25 years as a tech rep in the graphic arts, a lot of that time in prepress, the pressroom and the finishing departments. Part of what I learned was to determine what the viewing distance will be for a print. I bring this up because I had customers who specialized in printing outdoor billboards using the offset four color process. When you check dot quality and color registration on those images, you do not need a loop because of the size of the dots...they are that large. On the other hand, dot quality and registration on a full color image for a coffee table book definitely requires a loop. For my prints I have been given a simple rule to apply, take the diagonal of the print, double it and that is the normal viewing distance for that size image. Practical application, go to any fine art museum and while you can at times practically get your nose up to a painting, it's better viewed from a distance. I shoot a Nikon D7100; I shoot large fine JPEG and back it up in RAW. To check any image, I display it on a HD monitor which allows me to view any image I shoot as a measured 10" X 15" on screen. I have the ability to hit one button below the image displayed and that image then can be enlarged to poster size, calculated to be around 40" X 60". This is where I check that image for actual sharpness and detail. IF it looks to be sharp at that magnification, I will import the RAW file into Lightroom, do what post processing I want, then export for printing as a JPEG or TIFF. For my purposes I prefer either a 12" X 18" or a 16" X 24" sized print although I have done a few for friends up to 24" X 36". I will proof certain images as 8" X 12"s before committing to the larger sizes. I do proofs when I convert to monochrome and/or want to see an image on metallic stock vs. luster stock. I want to see it on paper! Most D7100 RAW files, exported from Lightroom, are JPEGs for me, have file sizes well over 10MB depending upon any cropping I may have done. This is how I do it for myself. One note, IF you are wanting a print done on canvas, know that the image will lose some sharpness just because of the texture of the canvas surface. This is also where viewing distance comes into the equation...how large is the print, how will it be displayed and how will it be lit.

Rongnongno Loc: FL

Regardless of your experience, to print or not to print depends on you alone (or anyone else who face the same question for that matter).

GalaxyCat Loc: Boston, MA

"I shoot large fine JPEG and back it up in RAW." Does that mean that you shoot 2 pictures and alternate JPEG and RAW?
Please tell me this. Also, what about "stock" photos? I understand that they have to be a minimum of 6.3 MP - do you know anything about that?

Thanks

lamiaceae Loc: San Luis Obispo County, CA

Wow, the discussion of resolution and print size can get crazy on the UHH. Myself and a couple others usually find ourselves at odds with many others. We will point out or talk about viewing distances, noting slide projectors, movie theaters, highway ad posters, and of course traditional art such as oil and other paintings in museums, and various rules as you point out with the diagonal of the print or format. But there are so many people on the UHH used to pixel peeking to judge everything that we get nearly flamed.

Personally I work in Photoshop via Raw and only go to JPEGs for printing or Web publishing. My PSD and TIFF files are often well over 100MB at 300ppi and 16-bit. And sometimes I'll even print from smaller TIF files. I recently got a 24MP APS-C camera and I just starting to deal with the huge Raw files I get. Seem to be around 25MB, as my older 16MP camera produced 18MB Raw files.

cthahn

"I shoot large fine JPEG and back it up in RAW." Would explain more what you mean.

jerryc41 Loc: Catskill Mts of NY

Good to know, especially if the image isn't very sharp to begin with.

Thanks for the info.

Rongnongno Loc: FL

Nevermind....

jerryc41 Loc: Catskill Mts of NY

I never do.

Jerry G Loc: Waterford, Michigan and Florida

Most DSLRs will record either a jpeg format file or a raw file or both of the same picture. Jpeg file can be saved at different resolutions (pixel count).

SonyBug

Haha, yes.

petercbrandt Loc: New York City, Manhattan

He's the thing: Beauty is in the Eye of the Beholder !
I shot an abstract of a buildings' design as an assignment for a major architectural firm in NYC. The image was blown up to 40"x60" as a print behind the doorman's desk. This image was shot with a Fuji S2 Pro (6mp).....years ago mind you!
The image was interpolated by Duggal Labs in NYC and the print was great, printed on Ultra matte paper at my request because I hate reflections in my prints.
What is the purpose of the print; display or examination of details (counting the red bricks?)
peterbrandt.com

burkphoto Loc: High Point, NC

I have a pro portrait lab background. Our lab standard *file* resolution was 250 PPI. That means, for an 8x10 print, you would need 2000x2500 pixels from the camera. This is based on Kodak's testing of perceivable resolution. They found that if you have 240 PPI in an 8x10 print, and you view that print at its diagonal dimension (12.8 inches), you cannot resolve (see) the dots. Make a 16x20 of the same image, without interpolation, and you would have 120 PPI before resizing to print. BUT, viewing the print at 25.6 inches, you would have exactly the same perception of the image. BUT, get closer, and you start to see individual pixels, stair-stepping, jaggies, etc.

So the "correct" file size for a given print depends on several factors. Are you going to have people pixel-peeping your work? Are you making a billboard? Will the print be viewed from AT LEAST its diagonal dimension, or closer?

Generally, we found through testing that SMALLER prints require more resolution than larger prints, because they are viewed more closely. A 4x6 or 5x7 inch print MIGHT need 300-400 PPI input to the print driver for optimal resolution. But 180 PPI input from the camera is usually enough for a 36x24... UNLESS the client will have pixel peepers viewing it from a foot away.

All these pixels-per-inch requirements are based upon original, UN-interpolated pixels coming from the camera... Files do get interpolated to resize them for printing. Our printers ranged in output resolution from 400 or 600 dpi on our mini-labs, to 2880x1440 dpi on large format inkjet printers. But we never required more than 250 PPI for any image.

PPI means the number of original, un-interpolated, from-the-camera pixels that will be spread over each linear inch of output, using whatever means necessary. dpi is a measure of printer or scanner resolution — i.e.; How many dots per inch am I printing, or how many samples per inch am I taking from a scanned surface? They are not the same, in most cases.

petercbrandt Loc: New York City, Manhattan

Still, after all those numbers, do you like the image ?...the feeling, the subject, or are you only looking at specs ?

SuperFly48 Loc: NE ILLINOIS

Once I get past the X's and O's (ISO and aperture and shutter speed and focal length and f stops and whatever else) and start shooting, then it all gets personal and subjective. That's what photography is to me...a time machine, a particular moment in time captured forever and I get to choose how that moment gets rendered after the fact. I do not copy cat Ansel Adams; I study his work and get ideas especially on subject composition and lighting.

As for hard copies of what I shoot, the source I use for my prints recommends I supply files of 300dpi, so that's the minimum I give them. In the end I am the final judge of the prints and subjects I have taken shots of. Do I like the final product? IF I get one shot per day that I am personally excited about, then I am happy. I went to Arizona last November. I took over 1800 plus shots. I printed 4 of them.

Not every shot is meant to be a wall hanger. Some shots might have historical significance; others something I liked and wanted to remember; still others might be taken for a "show & tell" session with family/friends because they were not there to see the subject in person; still others are test shots because I am experimenting.

petercbrandt Loc: New York City, Manhattan

I agree absolutely !!