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I have an old Takumar SMC 28mm lens. On the aperture ring, the marker for f/8 is in orange.

Is there any special reason for this? Is it just to mark the middle? Or is it just for style?

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https://www.amazon.com/SMC-Takumar-28mm-f3-5/dp/B005TU9NTA

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  • \$\begingroup\$ Please attach the image directly to the post so that the link doesn't 404 at some point in the future. \$\endgroup\$
    – Myridium
    Apr 16, 2017 at 0:06

3 Answers 3

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Many lenses from that era had the f/stop calculated by the lens designers to be the "sharpest" or "sweet spot" marked in a different color than the other f-numbers. A cursory survey of a couple of reviews of the lens in question indicate that the reviewers found f/8 to be the sharpest aperture setting.

As this answer points out, this particular lens also has an orange marking for the 9 feet (3 meters) focus distance marking which happens to be very near the 10.8 feet (3.29 meters) hyperfocal distance for a 28mm lens at f/8 when used with a 35mm film negative (36x24mm frame) enlarged to the size of an 8x10" print and viewed from 10 inches by a person with 20/20 vision.

The reason f/8, rather than f/5.6 or f/11 or any other f-stop, was selected as the aperture selected to show the hyperfocal distance is probably due to it being the lens' "sweet spot." All one has to do is line up the orange marks on the aperture ring, DoF scale, and the focus ring to set the lens at the hyperfocal distance using the lens' sharpest aperture.

Keep in mind that Nikon "D" lenses with aperture rings have the narrowest (highest f-number) marked in orange for a completely different reason: to assist the user in locking the aperture ring at that setting when using on a newer body that controls the selected f-stop via the camera's control system.

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If you move the focus ring, you will find the the 3m/9ft mark is also in orange. Many Pentax wide angle lenses use an orange marking at f/8 which corresponds to an orange hyper-focal focus distance mark on the focus ring.

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The orange marks are just for convenience for a quick hyperfocal distance reference.

When the orange marks are aligned, by using f/8 at a focus distance of 9ft, everything from about 6ft to infinity will be in focus. Stopping down to f/11 could increase the depth of field to maybe something like 6ft to infinity. (just a guess)

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  • \$\begingroup\$ But I always thought narrower aperture gives wider depth of field. Are you suggesting that going from f8 to f11 will give me a narrower depth of field? \$\endgroup\$
    – Scorb
    Apr 16, 2017 at 23:16
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    \$\begingroup\$ It didn't clarify completely. You said when the orange marks align you have the "deepest possible depth of field", yet in the next paragraph, you suggest adjust to f/11 would give you a deeper depth of field. The contradiction persists. \$\endgroup\$
    – Scorb
    Apr 16, 2017 at 23:58
  • \$\begingroup\$ Someone edited my answer and I have now removed the part that both you and I found contradicting. \$\endgroup\$
    – Mike Sowsun
    Apr 17, 2017 at 3:53
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    \$\begingroup\$ The reason f/8 was selected, rather than f/11 or f/5.6, is probably due to it being the lens' sharpest f-stop. \$\endgroup\$
    – Michael C
    Apr 17, 2017 at 22:17
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The lens comes from the good old days of film based street photography. At that time there was a philosophy of "f8 and be there" - you can read a bit more about it on https://www.adorama.com/alc/0013109/article/f8-And-Be-There.

The autofocus had not yet been invented, and speed was important. A solution was mounting a moderately wide angle lens and pre-focusing your camera.

Aligning the two orange marks gave you the optimal depth of field for street shooting. Note how the orange mark on focusing scale translates to hyperfocal distance at f8 (the orange f stop).

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