35mm-equivalent focal lengths for Kiev 88 lenses

More or less 6x6 (W) 6x6 (H) 6x6 (avg) 6x6 (diag) 6x4.5 (W) 6x4.5 (H) 6x4.5 (avg) 6x4.5 (diag)
Arsat 30mm f/3.5 18mm 19mm 12mm 15mm 16mm   19mm 17mm 18mm 18mm
Mir-26 45mm f/3.5 28mm 28mm 19mm 23mm 24mm   28mm 25mm 27mm 27mm
MC PCS Arsat 55mm f/4.5 35mm 35mm 23mm 28mm 30mm   35mm 31mm 33mm 34mm
Mir-38 65mm f/3.5 40mm 41mm 27mm 33mm 35mm   41mm 37mm 39mm 40mm
Arsat 80mm f/2.8 50mm 51mm 34mm 41mm 43mm   51mm 45mm 48mm 49mm
Vega 120mm f/2.8 75mm 77mm 51mm 61mm 65mm   77mm 68mm 72mm 74mm
Kaleinar-3 150mm f/2.8 90mm 96mm 64mm 77mm 81mm   96mm 85mm 90mm 92mm
Telear-5 250mm f/5.6
Jupiter-36 250mm f/3.5
150mm 160mm 107mm 128mm 136mm   160mm 142mm 151mm 154mm
Tayir-33 300mm f/4.5-22 180mm 192mm 128mm 154mm 163mm   192mm 171mm 181mm 185mm
MC APO Arsat 500mm f/5.6 300mm 321mm 214mm 257mm 273mm   321mm 285mm 302mm 309mm

What this all means

There's more than one way to work out the 35mm equivalent of lenses on medium format cameras, which usually use a different aspect ratio to 35mm film.

None of these methods are objectively correct. Depending on what you're shooting, one could make a case for using a different one for each photograph you take. (The diagonal and average numbers are close enough that you won't worry about the difference.)

Another way would be to calculate the diagonal angle of view, then work out what lens would be required to do this on 35mm format. I didn't.

Any of these methods will give identical results for comparing formats with identical aspect ratios, such as 35mm film vs 24x16mm digital SLR sensors, or 6x9 medium format.

Calculating it for other lenses

I've included all the lenses in the Kiev 88 system that I know of. If you want to work it out for some other medium-format lens (if you're fitting a Pentacon Six mount lens to a modified Kiev 88, for example), then divide the real focal length by one of these numbers:

I generated most of the table using a Python script I knocked up in five minutes. Do anything you like with this.

The calculations assume a 645 frame is exactly 42mm high. It's actually 41.5mm, but 42 is close enough, and is also a much better number.

Alternative method

TRA of the great Pentacon Six website has an even better method: Divide by two and add about 10%.


I got a list of Kiev lenses from the excellent Kievaholic site.