Photo purchased from … www.depositphotos.com
The Problem with Photos
There is a truism, somewhat unflattering in its wording: “garbage in, garbage out.” In commercial printing, whatever you start with in the way of photographic imagery, once you have digitized it (if it starts as a printed photo), opened it in your image editing software, placed the resulting TIFF photo into InDesign, and then handed off the file to the printer for imaging to the press plate, the image has degraded–at least a bit. Printing it on a paper substrate will degrade the image a bit further. Because of this, it is essential that you start with the very best image possible.
What do I mean by degrade? Two things for starters. The range from the darkest tone to the lightest tone in the image will narrow a bit in the journey from camera to offset commercial printing. This is called “tone compression,” the squeezing of the initial range from highlight to shadow.
In addition, the nuances of the visible transitions from highlights to midtones to shadows will be less evident than they were in real life, and less distinct to the eye than they were on the original image (film or digital) once you have printed the photos.
Another way of saying this is that the range and the detail in the subtle transitions from the lightest light to the darkest dark in the image will be minimized as you transition from the camera to the digital file to the custom printing plate to the final job on paper.
How Can You Improve the Quality of Your Printed Photos?
First of all, start with transparencies if at all possible. These have the greatest range from the lightest light to the darkest dark when compared to digital photos or printed photographs. (This is in the process of changing as digital technology improves. So you may want to do some research online for confirmation.)
Transparencies are essentially slides. They come in different sizes depending on the camera you’re using. Most commercial grade cameras bought for regular use are 35mm cameras. (Again, most cameras these days are digital rather than film-based, but back when I was an art director in the 1990s we used 35mm cameras almost exclusively.) Larger film formats were always better in that they captured more detail with less evident film grain (the silver halide crystals that made up the image on cellulose film for analog cameras). Some were 2 1/4” x 2 1/4” square-format cameras. Some cameras supported on tripods for extremely detailed work were 8” x 10” in format, yielding photos with both more and sharper detail in the transitions from one tone to another. Why is this? Because these large-format negatives or transparencies did not need to be enlarged as much as 35mm images for printing. (Even an 8” x 10” print made from a 35mm slide needs to be enlarged approximately 700 percent. A 2 1/4” image requires far less enlargement than a 35mm image, so minor flaws are less visible, but an 8” x 10” original is even better.)
So how does this translate to the digital images to which we have grown accustomed? If more image data affords a broader tonal range and more detail in the various levels from shadows to highlights, then a digital camera that captures more data—with a higher megapixel count—will translate into a better image in your camera and therefore a better image in prepress and final commercial printing.
You may even want to research image formats for digital cameras. From my reading on Camera Raw images, which are sometimes referred to as “digital negatives,” this format seems to be ideal (although it does create very large image files). Camera Raw captures the most picture information digitally, making it similar to working from not only a transparency but a large-format transparency at that.
However, if you do use a film-based camera, and you do choose to work from transparencies, be aware that if you examine transparencies on a light box, they will appear lighter than they will look when printed because they are back-lit. You have the same consideration when you’re evaluating images on a computer screen.
Resolution, Focus, and Depth of Field
One thing I have seen at various commercial printing plants is that if you start with a high enough megapixel image produced with a quality digital SLR (single lens reflex) camera, you can capture enough picture detail to be able to print the image on even grand-format inkjet equipment, large enough to create a mural. If you start with this good an original digital image, clearly you can produce large, crisp-focus images for your books and even posters.
Back in the ‘90s I learned all of this the hard way. I stated with a 35mm transparency and enlarged it for a poster. It was a promotional piece for a nonprofit educational foundation, and I hadn’t yet learned all of what I have noted above. I enlarged the image from 35mm to 18” x 24” poster size, and the film grain in the transparency became acutely visible. It looked like a pointillist painting (dot painting) or perhaps a mezzotint. Ouch.
A comparable flaw these days would be to start with a digital photo with too low an initial resolution and enlarge it (let’s say a 2” x 3” 72dpi image for the internet enlarged to a 4” x 5” format). You wouldn’t see film grain, as you would with a transparency, but you would definitely see pixellation (visible squares of color side by side making up the photo). This is one reason to always select a high-resolution image (300 dpi at the final size you intend to print it).
Flaws are always magnified, particularly if you enlarge the image. So the importance of choosing the highest quality photo pertains to image focus as well. If you start with either a film-based or digital image that is out of focus (or if your depth of field–the area of sharpest focus within a photo–is other than on your primary subject matter), the final printed product will be even more visibly blurred.
So What Can You Do?
Choose the image with the most picture data (digital or film). Make sure it is in crisp focus and the depth of field enhances the subject of the photo. Look at the image on a computer screen, but remember that the photos will appear lighter and the colors more saturated than they will once your commercial printing supplier has offset printed the job on paper.
Another thing you can do is check the images in Photoshop, analyzing their “histograms.” Histograms are vertical bar charts that show the number of pixels at a particular tone level from the darkest dark to the lightest light. You want a smooth curve with no gaps. You also don’t want either the shadow or highlight to be excessive (i.e., you don’t want the histogram chart to spike up at either end of the spectrum with too many completely white or completely black pixels).
Also, look for color casts, but don’t completely trust the accuracy of your (presumably uncalibrated) monitor in an uncontrolled (ambient lighting) environment (perhaps with a window, allowing the sun to change the colors on the screen throughout the day). Do a little research online to determine the proper histogram balance for the color channels (keep the Photoshop file in RGB–red, green, blue–format until you hand off the final, adjusted image to the printer in CMYK format). In this case you’re trying to avoid color imbalances: color casts. These show up on the online color densitometer readings, and on the internet you can find the proper Photoshop (RGB) amounts/percentages to keep all color channels in balance).
The Short Answer
So the best approach to avoid GIGO (garbage in, garbage out) is to give your printer the highest quality images (either film-based transparencies or high-megapixel digital images).
If there are any questions, I would encourage you to hand off the images to the printer for evaluation separately from the final art file submission (and with lots of lead time). A good prepress operator can look for all of the potential pitfalls I have enumerated and give you suggestions before you commit to final job files.
And then always ask for a physical color proof of any critical color work (like a poster or print book cover). If any of the flaws I have mentioned have slipped by, these will appear on a contract-quality color proof, and you can resolve the issues before offset printing your job.
This entry was posted
on Sunday, February 21st, 2021 at 12:53 pm and is filed under Photos.
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