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Author Topic: Focal length equivalents between formats  (Read 446 times)

Aram Hăvărneanu

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Focal length equivalents between formats
« on: January 11, 2019, 12:52:30 pm »

I was getting tired of wasting time recalculating every time I needed to determine which lens on some format I need in order to cover the same framing as another lens on some other format, so I wrote a very simple program and generated some tables for futher reference. You can find it here:

https://xw.is/wiki/Focal_length_equivalents_between_formats

I wrote this reference for myself, but I am sure others might find it useful as well.

Some notes:
  • This keeps tracks of aspect ratios.
  • This also encodes information about which tilt/shift lenses to use with stitching.
  • This lists all MF formats and some unusual LF formats.
If you have some favorite lens or focal length that is missing and want it added, please ping me and I will add it.

Alternatively, if you know for sure the exact image circles of Canon/Nikon TS lenses, or the image circle of the Hasselblad lenses with the TS adapter, also ping me up. I went with the numbers from 1) press releases, 2) documentation, 3) geometry.

Hope you find it useful.
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rdonson

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Re: Focal length equivalents between formats
« Reply #1 on: January 11, 2019, 06:04:14 pm »

Thanks, Aram.  This is helpful!!!
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Regards,
Ron

Dan Wells

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Re: Focal length equivalents between formats (notes on more format sizes)
« Reply #2 on: January 12, 2019, 02:25:41 am »

Very useful...Here are the other formats I could see including if you get a chance, plus some obscure format history. Is there any place where Canon's slightly smaller APS-C makes a difference? Sony sensors (used by most non-Canon cameras) are very close to 24x16mm (varying by a couple of tenths over the years), while Canon sensors are 22.3x14.9.

There are also a couple of other potentially useful sizes, by far the most important of which is Micro 4/3, which is actively developed and sold and relatively popular. Especially because it is the only common interchangeable-lens format (smaller than medium format) with an aspect ratio other than 3:2, it would be very useful to have in the chart.

APS-H was once a fairly common format, sitting in between APS-C and 24x36mm full frame. Most of its use was in Canon pro DSLRs  from the original EOS-1D of 2001 to the discontinuation of the EOS-1D mk IV in 2012. Sigma, Leica and Kodak have also made APS-H cameras, although only one slow-selling Sigma model remains in production, almost certainly far outnumbered by older Canon DSLRs still in service and probably outsold by the used market for old Canons.

1" sensors (very close to the old 110 film format) are used in the (mostly) discontinued Nikon 1 system and a number of cameras with fixed zoom lenses, plus many drones. As far as I know, the markings on most of the fixed-lens 1" sensor cameras are actually in full-frame equivalent?

Leica has used a 30x45mm "medium format" with a 2:3 aspect ratio, which has never really caught on, although they have recently announced an updated model with a new sensor.

The sizes above are of at least some practical interest - what's below is in the category of camera geeks only...

 In the realm of the truly obscure and probably unnecessary, but sold in the last few years,  Sigma has an entirely forgettable "APS-C" format that is even smaller than Canon's, close to midway between Sony APS-C and Micro 4/3.  Pentax's Q series has used a couple of different sensor sizes , all smaller than 1".

In the very early days of digital photography, there were even more odd smaller sizes of almost exclusively historical interest... The least exotic were the early Kodak DCS series - the first were smaller than 1" type sensors but larger than the Pentax Q series, while some later models were slightly smaller than Micro 4/3, and a few high resolution models were APS-H. From about 1999 to the demise of the DCS series in the mid-2000s, everything was either APS-C, APS-H or full-frame

 Minolta made a couple of  exceptionally odd DSLRs with optics in the body that projected light from roughly 1" and roughly APS-C fields of view onto tiny 1/2" sensors. They essentially had built-in Speedboosters... Nikon did the same thing early on, but the effective field of view was 24x36mm full frame.  I'm not sure there are more than a few of these early 1990s cameras left functional - maybe no more than there are 12x20" view cameras.

BetterLight's scanning backs aren't really fair, because they don't capture the image in a single exposure - they move a scanner head across the image plane. While they offer the largest capture area of anything sold to photographers today (72x96 mm or nearly 3x4"), there is one way to go even bigger... A BetterLight back is essentially a flatbed scanner attached to a 4x5" view camera, and there is nothing preventing an engineering-minded photographer from attaching a larger flatbed scanner to a larger view camera (admittedly unwieldy in the field).

I think that's all the formats anybody's ever built a digital camera with interchangeable lenses in?
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Two23

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Re: Focal length equivalents between formats
« Reply #3 on: January 12, 2019, 11:01:00 am »

Within reach I have cameras and/or lenses in the following formats:  half frame 35mm, Nikon DX, 35mm/FX, 4x4cm, 6x6cm 6x9, 4x5, 5x7, full plate (6.5x8.5 inch), 8x10.  Rather than try and convert lenses to different equivalents I simply think of them as "wide, normal, long."  This has simplified my life. :)


Kent in SD
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Dan Wells

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Re: Focal length equivalents between formats
« Reply #4 on: January 12, 2019, 11:59:59 am »

The one that causes no end of confusion among beginning photo students  (especially those who like to play around with vintage film cameras while also shooting digital) is the simplest of all... APS-C to full-frame! They've all heard that a 50mm lens is "normal". First of all, it isn't - it's always been slightly long, even on full-frame, where a true normal lens is 43mm.

Now add in the crop factor, and a true normal lens on APS-C is actually 28mm... Now, that's the wide-angle lens their grandfather gave them for their film camera.

Oddly, a 50 is actually closer to normal on the smaller digital medium formats (sensor diagonals around 54-55mm) than it is on full-frame.
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