Film SLR

Canon AT-1

The Canon AT-1 is a film slr that exposes a 36 × 24 mm frame on 135 film. Its crop factor is 1.00× — it is a full-frame format. Every number below is calculated for this exact film format.

Full frame (35 mm)1.00× cropCanon FD
Canon AT-1 camera
Photo: Nismo834, Public domain, via Wikimedia Commons
1.00×
Crop factor
36.0×24.0 mm
Image area
864 mm²
Area · 100% of full frame

Specifications#

Brand
Canon
Model
AT-1
Camera type
Film SLR
Lens mount
Canon FD
Film format
135 film
Image area
36.0 × 24.0 mm (Full frame (35 mm))
Crop factor
1.00×
ISO range
25 – 3,200
Focus
Manual
Exposure modes
Manual
Battery
4SR44 6V battery
Made in
Japan

Specifications merged from Wikipedia and Wikidata. Spot an error? Tell us.

Sensor size compared#

Medium format 44 × 33 mmCanon AT-1APS-CFour Thirds / Micro Four Thirds1" (one-inch) sensor
The Canon AT-1 frame (highlighted) drawn to scale against common formats. Its area is 100% of a full-frame sensor.

Focal length equivalents & field of view#

Multiply any focal length by 1.00 to get the full-frame field of view. Angles are for a rectilinear lens focused at infinity.

Lens on this cameraFull-frame equivalentHorizontalVerticalDiagonal
10 mm10 mm121.9°100.4°130.4°
12 mm12 mm112.6°90.0°122.0°
14 mm14 mm104.3°81.2°114.2°
16 mm16 mm96.7°73.7°107.0°
18 mm18 mm90.0°67.4°100.5°
20 mm20 mm84.0°61.9°94.5°
24 mm24 mm73.7°53.1°84.1°
28 mm28 mm65.5°46.4°75.4°
35 mm35 mm54.4°37.8°63.4°
40 mm40 mm48.5°33.4°56.8°
50 mm50 mm39.6°27.0°46.8°
56 mm56 mm35.6°24.2°42.2°
70 mm70 mm28.8°19.5°34.3°
85 mm85 mm23.9°16.1°28.6°
100 mm100 mm20.4°13.7°24.4°
135 mm135 mm15.2°10.2°18.2°
200 mm200 mm10.3°6.9°12.3°
300 mm300 mm6.9°4.6°8.2°
400 mm400 mm5.2°3.4°6.2°
600 mm600 mm3.4°2.3°4.1°
800 mm800 mm2.6°1.7°3.1°

Depth of field table#

Total depth of field at each subject distance, using a circle of confusion of 30.0 µm (the 0.030 mm full-frame standard scaled by the crop factor). Detailed tables: 24 mm f/1.8, 24 mm f/2.8, 35 mm f/1.8, 35 mm f/2.8, 50 mm f/1.8, 50 mm f/2.8.

FocalAperture50.0 cm1.00 m2.00 m3.00 m5.00 m10.0 mHyperfocal
22 mmf/1.85.3 cm22.1 cm92.8 cm2.24 m8.03 m∞8.98 m
22 mmf/2.88.4 cm35.0 cm1.56 m4.23 m34.1 m∞5.78 m
22 mmf/412.0 cm51.5 cm2.58 m9.74 m∞∞4.06 m
22 mmf/825.1 cm1.27 m103 m∞∞∞2.04 m
43 mmf/1.81.3 cm5.6 cm22.9 cm52.2 cm1.48 m6.35 m34.3 m
43 mmf/2.82.1 cm8.7 cm35.8 cm82.1 cm2.37 m11.4 m22.1 m
43 mmf/43.0 cm12.5 cm51.6 cm1.20 m3.59 m22.2 m15.5 m
43 mmf/86.0 cm25.2 cm1.09 m2.70 m11.0 m∞7.75 m
73 mmf/1.80.4 cm1.9 cm7.8 cm17.8 cm50.1 cm2.03 m98.8 m
73 mmf/2.80.7 cm2.9 cm12.2 cm27.7 cm78.1 cm3.21 m63.5 m
73 mmf/41.0 cm4.2 cm17.4 cm39.7 cm1.12 m4.71 m44.5 m
73 mmf/81.9 cm8.4 cm35.0 cm80.5 cm2.33 m11.2 m22.3 m
120 mmf/1.80.1 cm0.7 cm2.8 cm6.5 cm18.3 cm74.2 cm267 m
120 mmf/2.80.2 cm1.0 cm4.4 cm10.1 cm28.5 cm1.16 m172 m
120 mmf/40.3 cm1.5 cm6.3 cm14.4 cm40.7 cm1.66 m120 m
120 mmf/80.6 cm2.9 cm12.5 cm28.9 cm81.9 cm3.39 m60.1 m

Equivalent aperture#

Exposure is identical at the same f-number on any format; equivalence only describes depth of field and total light.

Aperture on this cameraFull-frame equivalent (depth of field)Hyperfocal at 43 mm
f/1.2f/1.251.4 m
f/1.4f/1.444.1 m
f/1.8f/1.834.3 m
f/2f/2.030.9 m
f/2.8f/2.822.1 m
f/4f/4.015.5 m
f/5.6f/5.611.0 m
f/8f/8.07.75 m

Night-sky exposure limits#

Longest exposure before stars trail. The NPF rule accounts for pixel pitch and is stricter than the classic 500 rule — use it for pin-sharp stars on high-resolution sensors. (NPF needs a known resolution and is omitted here.)

Focal length500 rule
14 mm (14 mm eq.)35.7 s
20 mm (20 mm eq.)25.0 s
24 mm (24 mm eq.)20.8 s
35 mm (35 mm eq.)14.3 s
50 mm (50 mm eq.)10.0 s

Open the NPF / 500 rule calculator →

Handheld shutter speed guide#

The reciprocal rule uses the equivalent focal length. High-resolution sensors may need one stop faster than this for pixel-sharp results.

Focal lengthNo stabilisation (1/equiv. focal)With 3-stop ISWith 5-stop IBIS
24 mm1/25 s0.3 s1.3 s
50 mm1/50 s1/6 s0.6 s
100 mm1/100 s1/13 s0.3 s
200 mm1/200 s1/25 s1/6 s

Frequently asked questions#

What is the crop factor of the Canon AT-1?

The Canon AT-1 has a crop factor of 1.00× relative to 35 mm full frame (diagonal 43.3 mm vs 43.3 mm).

What size is the Canon AT-1 frame?

36.0 × 24.0 mm (Full frame (35 mm)), an area of 864 mm² — 100% of full frame.

What lens mount does the Canon AT-1 use?

The Canon AT-1 uses the Canon FD (flange distance 42.00 mm).

How long can I expose the night sky with the Canon AT-1?

With a 20 mm lens (20 mm equivalent) the 500 rule gives 25 s.

Sources & licences#

Last updated October 03, 2026 · How we calculate · Sources

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