# Pentax 645 — Camera mount flange focal distance and adapter feasibility

For Pentax 645, flange focal distance (mm) is 70.87 mm; mount type is SLR; format is 6×4.5 cm; production years is 1984–, verified against its source on 2026-08-13.

- **Mount name:** Pentax 645 _(verified: appears in the quote below)_
- **Flange focal distance (mm):** 70.87 mm _(verified: appears in the quote below)_
- **Mount type:** SLR _(verified: appears in the quote below)_
- **Format:** 6×4.5 cm _(verified: appears in the quote below)_
- **Production years:** 1984– _(verified: appears in the quote below)_
- **Throat diameter (mm):** 61.2 _(per graphics.cornell.edu, not stated by the source above)_

## What the source says

> Pentax 645 | 70.87 mm | SLR | 6×4.5 cm | 1984–

## Sources disagree

More than one authority states this, and they do not state the same
thing. Both are reproduced with the source each came from.

### Flange focal distance (mm)

en.wikipedia.org says flange focal distance (mm) is **70.87 mm**, as of 2026-08-13.

> Pentax 645 | 70.87 mm | SLR | 6×4.5 cm | 1984–

Source: https://en.wikipedia.org/wiki/Flange_focal_distance

graphics.cornell.edu says flange focal distance (mm) is **70.87**, as of 2026-08-13.

> Pentax 645 | bayonet | 70.87 | 61.2 |

Source: https://www.graphics.cornell.edu/~westin/misc/mounts-by-register.html

briansmith.com says flange focal distance (mm) is **70.87 mm**, as of 2026-08-13.

> Pentax 645 | 70.87 mm | SLR | 6X4.5 cm

Source: https://briansmith.com/flange-focal-distance-guide/

allphotolenses.com says flange focal distance (mm) is **70.87**, as of 2026-08-13.

> Pentax 645 | 70.87 | Medium format camera

Source: https://allphotolenses.com/articles/item/c_6.html


### Mount type

en.wikipedia.org says mount type is **SLR**, as of 2026-08-13.

> Pentax 645 | 70.87 mm | SLR | 6×4.5 cm | 1984–

Source: https://en.wikipedia.org/wiki/Flange_focal_distance

graphics.cornell.edu says mount type is **bayonet**, as of 2026-08-13.

> Pentax 645 | bayonet | 70.87 | 61.2 |

Source: https://www.graphics.cornell.edu/~westin/misc/mounts-by-register.html

briansmith.com says mount type is **SLR**, as of 2026-08-13.

> Pentax 645 | 70.87 mm | SLR | 6X4.5 cm

Source: https://briansmith.com/flange-focal-distance-guide/

allphotolenses.com says mount type is **Medium format camera**, as of 2026-08-13.

> Pentax 645 | 70.87 | Medium format camera

Source: https://allphotolenses.com/articles/item/c_6.html


### Format

en.wikipedia.org says format is **6×4.5 cm**, as of 2026-08-13.

> Pentax 645 | 70.87 mm | SLR | 6×4.5 cm | 1984–

Source: https://en.wikipedia.org/wiki/Flange_focal_distance

briansmith.com says format is **6X4.5 cm**, as of 2026-08-13.

> Pentax 645 | 70.87 mm | SLR | 6X4.5 cm

Source: https://briansmith.com/flange-focal-distance-guide/


## Source

- https://en.wikipedia.org/wiki/Flange_focal_distance
- https://www.graphics.cornell.edu/~westin/misc/mounts-by-register.html
- https://briansmith.com/flange-focal-distance-guide/
- https://allphotolenses.com/articles/item/c_6.html

Last verified: 2026-08-13. Review by: 2028-08-12.
Part of [Camera mount flange focal distance and adapter feasibility](https://referencesource.org/camera-lens-body-adapter-compatibility/).