Focal lengths on different formats

Consumer photographic lenses are almost always sold by their focal length when used on a 35mm camera (or full-frame professional DSLR). It’s already confusing enough to work out what their effective focal length is when used on an APS-C sensor (most consumer DSLRs), but since I’ve been getting into medium-format photography it’s even more confusing to work out what each focal length does what on which camera.

So I’ve done a little research, and prepared a table. I’ve included data for five “common” photography formats with their crop factors. The numbers are the approximate focal lengths in millimetres. Of course the boundaries for each category of lens are rather woolly at best.

Film or sensor format
Lens type APS-C 35mm 6×6cm 6×7cm 5×4in
Fish eye 10 16 30 35 45
Super wide 12 20 40 45 65
Wide angle 17 28 50 55 90
Normal 30 50 80 90 150
Short telephoto 49 80 150 180 270
Medium telephoto 123 200 350 420 520
Long telephoto 185 300 500 600 800

KMZ Zorki 4

Released 1956

This is my first rangefinder camera. It’s also my first compact camera that has interchangeable lenses. It has some pretty unusual quirks, but it’s fun. There is some excellent glass available in M39 mount so this is a high-quality photographic tool, and a good alternative to an SLR.

See all photos taken with the Zorki 4.

Zorki 4
Zorki 4

At a glance

Lens M39 mount
Film 135
Focus Coupled rangefinder
Meter None

Kodak Brownie Model I

Released 1957

This is another “dumb” box camera with no manual controls, like the Conway. It’s in mint condition and with its original case. I like it because its shutter is more reliable than the Conway.

See all photos taken with the Brownie I.

Kodak Brownie Model I
Kodak Brownie Model I

At a glance

Lens Fixed 100mm f/14
Film 620 (6×9)
Focus Fixed
Meter None

Halina Paulette Electric

Released 1967

This is a simple viewfinder camera with an uncoupled selenium light meter. It’s reasonable, and OK to use. What the light meter adds in usability over fully manual cameras, the lack of any kind of focussing aid takes away.

See all photos taken with the Paulette.

Halina Paulette Electromatic
Halina Paulette Electromatic

At a glance

Lens Fixed 45mm f/2.8
Film 135
Focus Guess
Meter Uncoupled selenium

LOMO Lubitel 166 Universal

Released 1980

This is my first TLR. I saw it at a car boot sale and snapped it up for a bargain price. At the time of writing, this is my only medium format camera with the ability to focus, and with control over the aperture and shutter.

It’s much more rewarding to work with than a box camera, and good fun to sling it round your neck and use the waist-level finder.

See all photos taken with the Lubitel.

LOMO Lubitel 166 Universal

At a glance

Lens Fixed 75mm f/4.5
Film 120 (6×6)
Focus TLR with ground glass
Meter None

Braun Paxette Electromatic II

Released 1959

The Paxette is quite a nice compact, with a fixed shutter speed at 1/40, but variable aperture and focus. The basic selenium meter doesn’t work but that’s OK. It’s still perfectly usable as a manual camera.

See all photos taken with the Paxette.

Braun Paxette Electromatic II
Braun Paxette Electromatic II

At a glance

Lens Fixed 40mm f/2.8
Film 135
Focus Guess
Meter Uncoupled selenium (broken)

Olympus OM101

Released 1988

This is yet another not-very-interesting SLR. The most noteworthy point is that it has “power focus”. This is manual focus, but adjusted using a thumbwheel and an electric motor, rather than by twisting the lens barrel.

Unusually for an SLR, exposure is fully automatic unless you buy the additional “manual control unit” which clips on the side and has knobs to adjust the aperture and shutter speed.

Olympus OM-101
Olympus OM-101

At a glance

Lens Olympus OM mount
Film 135
Focus Power focus with split screen
Meter Auto