Print and Image Sizing Guidelines

Print and Image Sizing Guidelines
Alan Ranger Photography(44) 781-7017994info@alanranger.com

Why print?

 Having spent countless hours capturing images, editing images and probably re-editing and selecting images your now at the stage of getting a set of prints ready.

 You may think that the job is done already but the print is the final part of the workflow (share) and is as every bit important as the previous four stages:

 

see | design | shoot | enhance | share

 

 This is especially a truism when it comes to the RPS.  I often joke about the judges smelling the ink on the paper and waxing lyrical about paper choices more than the photograph itself.   Joking aside, the assessment for any panel quite rightly relies on evidence that the photographer (applicant) also understands, and presents, the images to a professional and competent standard.  

 The printing part (sharing) of the panel has equal importance to the design (creative/framing), shoot (technical execution), enhance (editing and presentation) as the first stage of showing what the photographer sees and interprets.

 Nowadays, few people choose to print images as it’s so much easier to share electronically through social media and photo websites.  As such, many photographers don’t have the knowledge and understanding of print resolution, aspect ratios, mounting, paper choice and the plethora of challenges that come with making the print.  In fairness, even as professional from the digital age, I must work things out each time I go to print too, though I have done enough exhibitions and other print required tasks to have a reasonable understanding.

 “The negative is comparable to the composer's score and the print to its performance. Each performance differs in subtle ways.” Ansel Adams

 My digital photography interpretation of Ansel's quote is “the digital file is the score, and the print is the performance.”

 Given that I have many clients, on various courses, and other events wishing to create prints, I felt a guide to the considerations and technicalities would be helpful.


Image aspect ratios:

 So, what about aspect ratios? In its simplest form, a print aspect ratio is simply a measurement of its width compared to its height, in the form of a ratio. For example, a full frame image taken from a SLR camera, without any cropping, is in the ratio 3:2. Or expressed another way, the width of the image is 1.5 times the height of the image.

 How does aspect ratios relate to cropping?  The image below is a full frame 3:2 image.  If we printed this as a 6×4” print, it would not need cropping but what if we wanted this image in another common print format – a 10×8”? 

 This would unfortunately mean cropping part of the image –possibly an important part of the composition.  The reason is that, although the 10×8” print is significantly larger than a 6×4”, its aspect ratio is 5:4.  In another words, the larger 10×8” print’s aspect ratio is squarer. 

Image Aspect Ratio

What about other common small print formats – the 7×5?  It’s are more elongated than the 10×8” but squarer than the 6×4”.  If this seems more confusing, think of in terms of the width as a multiple of the height (or just refer to this table below!).  

Remember the aspect ratio has nothing to do with the quality and size of the photo it is just the shape of the rectangle – viewing area.

Image Size Ratio

Paper sizes:

 We are all familiar with standard paper sizes when it comes to office and home printers.  However, the camera doesn’t naturally conform to those standard dimensions when we are printing a photo (uncropped) from a digital SLR camera. 

 The camera photo dimensions (aspect ratio) are based on the sensor or film size, so do not fit the page size easily or equally (the same amount of white space around the photo)

 Therefore, we have to convert image size to fit standard paper sizes to fill as much of the paper area without cropping the image.  Here you can see that the paper aspect ratios do not align perfectly to image aspect ratios.  Nearly all the paper sizes in the table below have an aspect ratio of 1.41 which is the closet match to 7 x 5 image aspect ratio (1.4)

Paper sizes and ratio

Viewing distance and print resolution:

 If the calculation of paper size and image sizes was not already complicated enough, we also need to consider image resolution. Meaning acceptably sharp at “normal viewing distances”.

 Acceptably sharp is determined by the viewing distance and medium the image is presented on.  Assuming you are printing images for viewing rather than seeing on as a projected image (or Mobile device and computer) then a viewing distance of 1-3 feet (within arm’s length) is considered the normal range for determining sharpness and details of the print. 

 How do you calculate minimum viewing distance?

 A generally accepted rule of thumb is that an appropriate minimum print viewing distance is simply the diagonal length of an image multiplied by 1.5

 For example, a 36" x 54" image would have a diagonal length of about 64.9". Multiplying 64.9" by 1.5 results in a viewing distance of about 97.3" or 8.1 feet

Viewing distance for photographs

Viewing Distances

In addition to this the PPI needs to be sufficient to render the image sharp at that viewing distance and size of image

 PPI stands for “pixels per inch.” The more pixels per inch, the higher the image resolution. You can see from the chart, below, that PPI, or resolution, is inversely related to the output size and viewing distance. The larger your output AND greater your viewing distance, the fewer pixels per inch that are needed in order to ensure sharp appearance.

 Therefore, the image resolution must be sufficient in megapixels to ensure you can produce a high-quality print at 200 PPI for minimal, and 300 PPI for high quality as close viewing distance and less than 200 PPI when viewing from greater distances.

Print resolution and PPI

The maths involved to come up with that size print is to first divide the number of pixels in the width of the file by the 200 DPI. (2,000/200=10).

 Next, divide the number of pixels in the height of the file by 200. (1600/200=8). So, there you have it. A file size of 2,000 pixels X 1600 pixels can be printed to make a good quality 10 X 8 photo when printed at 200 DPI.

 If you decide to make a print at 300DPI from the same image file, you will have a print with better resolution. However, the maximum size for a quality print will be smaller.

 The maths would be.... 2,000/300=6.8. Next, 1,600/300=5.3. So, if you round the numbers out, the maximum standard size for that print will be about 7 X 5.

 The key connection to viewing distance here is that due to the optics of the human eye, a print that is 3x farther away requires exactly 3x less resolution to maintain the same visible quality!

So, in the case of the 36" x 54" image, having 1/3 of the resolution at 100 PPI is equally compensated for by the 3x longer viewing distance.

Though printing a fine art photograph at 100 PPI is considered completely unacceptable to some, if a photographer intends for a large print to only be viewed from 8 feet away or more, this is reasonable.

Viewing distance and resolution of photograph

Takeaway - 300 PPI for a 10" x 14" is the largest print size generally felt as comfortably sharp when viewing at arm's length, at which point 300 PPI is just beyond the capabilities of the human eye.  Smaller than this then 300 PPI is ideally required, larger than this then 200 PPI or less is acceptable at the appropriate viewing distance.

Image aspect ratios and photo paper sizes:

The table below shows the ideal resolution of the image required at 300 PPI to be printed at a size of approximately A4 (8.3 x 11.7 in).  This is the expected minimum size for RPS panels.

 The mount sizes shown is 16 x 12 in.  Approx. A3 size

Picture A3 paper with an A4 Cut-out/Window centred on the A3 to get an idea of image space and mount space.

A3 Mount with A4 Cut-out/Window

 

To calculate the size of the image space for any given aspect ratio, (thus avoiding any cropping) and leave 4 inches between the image border and mount border,

 1.      specify the target longest edge size of the image

2.     divided by the aspect ratio longest side

3.     to give you a scaling factor of nn

4.     then multiple the smaller sides aspect ratio by nn to calculate the short dimension.

 Example when wanting a print size of around 12 inches on the longest side with an image in 2:3 aspect ratio

 1.      12 inches

2.     Divided by 3 (longest edge aspect ratio) = 4

3.     4 is the scaling factor (nn)

4.     2 x 4 (2 is the shortest side aspect ratio, 4 is nn factor) = 8

 Result is 8 x 12 inches

 To calculate the image resolution and megapixels for the image dimensions.

 1.                Longest edge multiplied by 300 (300 being PPI)

2.               Shortest edge multiplied by 300

 Result: Pixel Dimensions

Next multiple the x & y dimensions to calculate the Megapixels needed for 300 PPI.

 Example:

 2:3 aspect ratio printed at 8 x 12 inches.

 1.      12 x 300 = 3,600

2.     8 x 300 = 2,400

 Result pixel dimensions 2,400 x 3,600

 Megapixels = 2,400 x 3,600 = 8.64 million

 I recommend a 16 x 12 inches mount (Approx. A3) with Max photo width of 12 inches (Approx. A4 image size) as below:

Image size calculation for mount size

Creating test prints and choosing paper

 There is a large choice of papers when it comes to fine art prints.  The choice of paper is largely a personal one and it does depend on what paper suits a particular image.

 For example, portraits print well on Permajet Matt Plus and landscapes print well on Hahnemuhle – Bamboo.  Just my opinion but it is worth getting some test prints on various papers before committing to a final choice.   Remember if you are putting a body of work/panel together its strongly advised to stick to one paper for all the images in that panel/exhibition/body of work to keep the coherence.

One Vision Imaging Print Lab Paper Choices for fine art prints

Rather than ordering individual prints on various papers, I create a combined image file with all the images on one sheet as shown below:

test print with multiple images on one pape

This can be done simply in Lightroom using the print module as follows:

  • Set page size to A3 in Page Set-up. 

  • Then create a custom contact sheet with the following dimensions:

contact sheet layout for 10 panel images

Print to JPG file rather than printer in Lightroom:  

 This will produce and A3 Size sheet as a single jpg file at high resolution enough for getting your panel/body of work printed on various papers to compare.  You can also do this via Photoshop too if you are comfortable with placing images onto a new A3 white canvas.

Print to JPG file

This will produce and A3 Size sheet as a single jpg file at high resolution enough for getting your panel/body of work printed on various papers to compare.  You can also do this via Photoshop too if you are comfortable with placing images onto a new A3 white canvas.

 To view the video on how to do this and upload and order test prints

How to create a single page with multiple images on and order test prints with One Vision Imaging Ltd on different fine art papers

Ordering and sizing final image printing

 Checklist:

  1.  All images are at sufficient resolution/Megapixels to meet the requirements of 300 PPI for the size of print.

  2.  You have uploaded full resolution JPGs or Tiff Files to the print lab with a standard colour profile – Adobe RGB or SRGB

  3.  All images have been cropped to standard aspect ratios OR you have calculated the dimensions for each image size and mount size with cut-out/window.

  4.  You have chosen a fine art paper that works for the whole collection/panel.

 I recommend (without any commission or prejudice) One Vision Imaging Limited for all my fine art prints.  The print quality and production are always first class and they have excellent customer service so will be more than happy to help you through the process if my guide is beyond what you can process easily.

 You first need to register on their site and create a profile so that you can upload your images into a collection and then order prints, framed, unframed or mounted accordingly.  Create a profile with One Vision Imaging.

 To see how to order your prints with a custom size and mount only watch this video.


I would really welcome your comments, questions, debates or any engagement on this post, so please feel more than welcome to post in the comments box below. Many thanks