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 |

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.

**Method 1:**divide the width of the 120 frame by the width of the 35mm frame, then divide the medium-format focal length by the resulting number. (**"W"**in the table above.)**Method 2:**do the same as above, but use the height of the two frames. (**"H"**in the table above.)**Method 3:**divide the medium-format focal length by the average of the magic numbers calculated above, or average the two resulting numbers from the above. (**"Avg"**in the table above.)**Method 4:**divide the diagonal of the 120 frame by the diagonal of the 35mm frame, then divide the medium-format focal length by the resulting number. (**"Diag"**in the table above.)**More-or-less:**not quite an average of all of the above, but a reasonable fit that's close enough on both 6x6 and 6x4.5 to a 35mm focal length that is actually used.

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.

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:

**6x6 (W):**1.56**6x6 (H):**2.33**6x6 (avg):**1.94**6x6 (diag):**1.83**6x4.5 (W):**1.56**6x4.5 (H):**1.75**6x4.5 (avg):**1.65**6x4.5 (diag):**1.62

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.

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.