Why are photo paper sizes imperial?

A correspondent recently complained that a university quoted photographic paper sizes to him in imperial units. This reminded me of an unpleasant discovery I made some years ago.

Following an altercation with a photographic shop (over requesting sizes in cm) I once did a little research and discovered that photo paper sizes follow an international agreement which is imperial. Thus the popular 6 x 4 size actually is 153 x 102 mm (not 15 x 10 cm as I had assumed). Either way it is a stupid anomaly as it does not correspond to the A6 size, which is 148 x 105 mm. Hence, 4 prints will not fit on to an A4 sheet.

This is all presumably because of the historic dominance of the American photo industry, but you would think that Agfa, Fuji etc would have challenged it before now. Does anyone know whether the position is the same in continental Europe and elsewhere in the world?

Author: UK Metric Association

Campaigning for a single, rational system of measurement

18 thoughts on “Why are photo paper sizes imperial?”

  1. I seem to recall recently reading an article on this although I can’t currently find the link. The rationale for the article was to explain the reason why mm should be used and cm shouldn’t.

    The story was that in it’s early years, Kodak decided to be completely metric. The film department used “mm” and since then photographic film has been measured that way. The paper department on the other hand decided to use cm instead. This didn’t catch on and eventually people started using inches instead.

    I don’t know if there is any truth in this story… if I find the link I’ll pass it on.


  2. The photograph that most people buy from a university is the graduation photograph. Some people like to frame the graduation photograph and the degree certificate in matching frames. Of course, if the frames are the same size, it will look a lot better. However as described above, photographs tend to be 254 mm x 203 mm, but degree certificates are often A4 sized (297 mm x 210 mm).

    There is one ray of light – on the way home from work this evening I popped into a photographic suppliers (Jessops) and looked at the paper that was available. There were two principal sizes for the DIY photographer armed with an ink-jet printer 4� x 6� (102 mm x 153 mm) and A4. I just wonder how long it will be before the professional photograph printing equipment used by the various photographic shops start making prints available in A4 sized paper?


  3. There were many differing plate camera sizes. The standard whole plate size was 8 1/2 x 6 1/2, (inches), and quarter plate was 4 1/4 x 3 1/4 (the common press camera size as seen in old movies) Printing paper was made to match, I suppose originally so you could make contact prints. These sizes didn’t match up later to film sizes – the popular 35mm still camera film has a usable area 24 mm x 36 mm and the Rollei etc was 6 cm x 6 cm so there was always a bit of waste if you wanted to print the whole of a negative. It’s too late to start trying to change it now.. but I guess 6 x 4 is just a handy size which happens to match the 35mm film ratio and has stuck for digital. Oddly enough, movie film has always been in metric for width, (8, 16, 35, 70 mm etc) but imperial for length (50, 100, 400 and 1000 ft rolls, worldwide). Thanks to Eastman.
    PS I’ve been both a still and a movie film cameraman. With digital, who knows what the standard will eventually be.


  4. I believe Pat Naughtin of Australia has written about Kodak and how mm and cm made a difference there in terms of adoption of metric just as the use of mm vs cm has made a difference in the adoption of metric in the Australian building trades vs. the garment industry.


  5. There are a number of differing technologies that are used for the presentation of pictures, all of which have different length to breadth ratios. Here are a few popular devices and their associated ratios:

    1.29 – US letter paper (11� x 8.5�)
    1.33 – Computer screens (800 pixels x 600 pixels)
    1.41 – Metric sized paper (A4 = 297 mm x 210 mm)
    1.50 – 35 mm film (36 mm x 24 mm) and 6in x 4in photographic paper
    1.77 – Digital Television (Ratio 16:9)


  6. Yesterday morning I bumped into an acquaintance who is a professional
    photographer – he runs a photographic shop and also does weddings,
    family portraits etc. He told me that he uses industrial rolls of
    photographic paper and selects the photograph sizes by pushing the
    buttons on the machine. He told me that it was possible to get A4
    photographs, but the choice of frames was limited.


  7. Martin Vlietstra Says:

    2007-09-03 11:57

    “He told me that it was possible to get A4
    photographs, but the choice of frames was limited.”

    So how does one create enough of a demand for A4 frames that they become more common? One would think that with the use of A4 photo paper in home printers, that there would be an increased demand, unless people who do their own photo printing don’t use frames. They may go mostly into photo albums. Or they find a way to make an A series print fit into an existing frame.

    I’m just wondering though if printed photos will die out as there is less and less of a need for them. Most digital pictures can be viewed on a screen. I’ve even taken old pictures and scanned them before they fade away as they usually do over time.

    A relative who was married a few years ago had no prints of their wedding at all. They had every photo and a wedding video put on a CD. They were able to make their own copies and pass them on to those that wanted them. At least the CD is metric (120 mm exactly in diameter). If you want to view their wedding photos, you do so on screen.

    Some people store their photos on line. You can view them by going to a known website. No need to waste money printing out photos that can get lost or damaged.

    I’m not sure if the digital photos are sized in any particular units. What one usually sees is pixels. Since screen dot pitch is in millimetres, then pixels can be related to a given number of millimetres.

    It just seems that technology and habits based on imperial have a limited existence. They fade over time, like printed photos.


  8. Martin Vlietstra listed some important aspect ratios above. To that list must be added the “old” television ratio of 4:3 (1.33333….). Most digital compact cameras use that ratio, meaning when printing on 4″x6″ paper (it seems we can’t accurately call it 10cm x 15cm), either the image has to be cropped at the top and bottom, or the paper has to be cut at one or both sides. Few ink-jet photo-printing paper companies offer (nominally) 10cm x 13.3cm paper. Most up-market digital SLR’s, however, use a 3:2 (aka 1.5) aspect ratio.

    Incidentally, the 16:9 TV ratio is not a “digital” television ratio. 16:9 was used in analogue TV (“PAL Plus”), and many television channels broadcast digitally but in 4:3.

    There is lots of interesting stuff about aspect ratios and paper sizes in Wikipedia: http://en.wikipedia.org/wiki/Aspect_ratio.

    Someone asked why how A3, A4 and A5 could be called metric, as their sizes are not round numbers of millimetres (let alone centimetres)…. (yes, I know, and you know, but try explaining how logical it is to someone who doesn’t know!).


  9. Sorry, Martin, I know you listed 1.3333 as a computer screen ratio, but I meant it as a TV ratio as well. Anyway, computer screens also come in 5:4 (1.25), 16:9 (1.77777) and 16:10 (1.6) ratios.


  10. The digital camera market has yet to settle on a standard size for the sensors that have replaced the film itself. Some top-end cameras use ‘full-frame’ sensors equivalent in size to 35mm film: most use smaller sizes. The latest system from Olympus is known as the Four Thirds system, because the sensor has a diagonal measurement of four-thirds of an inch (ie. 1 1/3″)


  11. It always confuses me when I go to get photos developed (as I don’t use up films particularly fast!) and they ask what size of prints I want. I just can’t visualise numbers in inches – they’re the unused upside-down numbers at the bottom of the ruler, after all! If it wasn’t for the fact that most photolabs have sample displays on the counter, I’d be stuck to work out what size I want to choose. I don’t see why they can’t just display the size in cm as well. It’s especially unfair to children proudly taking their first film to be printed (as I recall myself), although I guess nowadays a child’s first camera is far more likely to be digital!


  12. I hope this remark isn’t too erudite but as I understand it people in the visual arts and architectural world have always revered the so called “Golden ratio” as being aesthetically appealing.
    It is defined to be a rectangle whose proportions are such that the ratio of the shortest side to the longest is the same as that of the longest side to the sum of the two. It works out to be about 1:1.618. It pops up elsewhere too. For example it is the ratio that consecutive terms of the fibonacci sequence converge to, ad infinitum (the sequence beginning 1, 1, 2, 3, 5, 8, … where each term is the sum of the previous two – note that 5:8 is 1:1.6 already).
    Maybe the TV/Computer display industry should consider this. It would be much easier to implement in mm than in inches!


  13. Clifford Dudley Says:
    September 11th, 2007 at 11:10
    … Most digital compact cameras use that ratio, meaning when printing on 4″x6″ paper (it seems we can’t accurately call it 10cm x 15cm) …

    Clifford, we can’t “accurately” call them 4″x6″ either. That would make them exactly 152.4 mm x 101.6 mm. At least the standard (metric) sizes are in whole mm, even if not whole cm.


  14. The Golden Ratio may be aesthetically pleasing, but there’s absolutely no chance of it being adopted for TV or camera use, as it’s not really relevant in this particular context, and standards, which can be justified on the grounds of compatibility with existing movie technology, have already been expensively devised and implemented.

    The Golden Ratio applies to the aesthetics of objects which, combined as a whole, make up a greater part of the scene, and do so in a visually-pleasing manner, but our stereoscopic vision gives us a wide field of view and so as far as TV is concerned, a wider field of view that better matches our vision is better (and still allows us to see “Golden Ratio” objects within it, with adequate background to frame that view). It is this wider format (16:9 or 1.78:1) that gives widescreen TV or films their visual impact.

    Sadly, even this format isn’t wide enough for many movies which have been filmed in an even wider – and even more impressive – widescreen format. However, the developers had to make choices when implementing widescreen TV, taking into account considerations such as how wide a picture tube could be reliably constructed, limitations on broadcast bandwidth, etc.

    Of course, if one wants to emphasise the Golden Ratio in a photographic print for artistic reasons, one can easily do so by cropping the print accordingly, no matter what size of paper it was originally printed on!


  15. I have read all the comments , but they do not answer a problem I have recently come upon. I have a new Brother printer and its list of paper sizes has names such as Photo L and Photo 2L as well as just Photo, but no dimensions are given. There are also Postcard and Postcard 2. Can anyone tell me the sizes of these papers. I do not mind Metric or Imperial. I have asked Brother, but they just refer me to a site that explains the International DIN standard and the American standard.

    Many thanks,
    Michael Bennett


  16. The ISO 216 size standard is a ‘metric based’ standard because the base sheet size A0 is 1.0 m^2. But ISO 216 is not part of the metric system because smaller sheets are derived in powers of 2 — not 10. Thus A1 is 0.5 m^2, A2 is 0.25 m^2, etc. Other than A0, two other base sizes are also used: B0 is sqrt(2) m^2 and C0 is sqrt(sqrt(2)) m^2. The sizes are ordered such that an A4 letter fits in a C4 envelope, which fits in a B4 envelope.

    The aspect ratio specified by ISO 216 is 1:sqrt(2) in order to maintain a consistent ratio as the longer side is successively halved. For example, assume the dimensions are x (short side) by y (long side). Then cut the paper in half along the longer side to get y/2 (short side) by x (long side). For the ratio short:long to remain the same, x/y must equal (y/2)/x = 1/2 * y/x. Thus (x/y)^2 = 1/2, meaning the ratio is 1:sqrt(2).

    A system based on subdividing in tenths would not be practically useful. The aspect ratio would have to be 1:sqrt(10), approximately 1 to 3.16. A0 would be 562mm x 1778mm (22.1″ x 70.0″),; A1 would be 178mm x 562mm (7″ x 22.1″); A2 would be 56mm x 178mm (2.2″ x 7″); etc. These sizes are practically useless. Subdividing by 2, on the other hand, shrinks the sheet size much more gradually and produces a manageable 1.41 aspect ratio — which together yield many more useful sheet sizes.

    For pictures, an A4 sheet yields

    1 A4 (8.3″ x 11.7″) => S8R 8×12
    1 A5 (5.8″ x 8.3″) => 6R 6×8 &
    1 A6 (4.1″ x 5.8″) => 4R 4×6 &
    2 A7 (2.9″ x 4.1″) => 2R 3×4

    A B5 sheet yields

    1 B6 (4.9″ x 6.9″) => 5R 5.0×7.0 &
    1 B7 (3.5″ x 4.9″) => 3R 3.5×5.0 &
    2 B8 (2.4″ x 3.5″) => 1R 2.5×3.5


  17. I had same problem as Michael Bennett above, trying to find photo paper size of L / 2L on my Brother printer, and I came here.

    The answer is on Wikipedia –

    L = 3.5 x 5 inch = 89 × 127 mm
    2L = 7 x 5 inch = 127 × 178 mm


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