I've dug up my dad's old Pentax K1000 SE, along with his old lenses, and picked up some 400 film. I'm wondering which of these lenses I should go with to get the best shots tonight (outdoors, no flash):

  • SMC PENTAX-M 1:1.7 50mm
  • SMC PENTAX-M 1:3.5 135mm
  • Vivitar Series 1 70-210mm 1:3.5

I'm leaning towards the 50mm, because I think it has the lowest f-stop, meaning it lets in more light? But, I might want to have a bit more of an ability to zoom to frame my shots?

Also, I'm not sure if the meter still works, or if the battery was just dead, but approximately what sorta shutter speeds should I be using (so that I can hopefully get something reasonable if the meter doesn't work)?


Update: Thanks for the advice. Here are the best results:



I definitely see the trade off from a wide open aperture: the depth of field is pretty limited. But, they seemed to work.

(I'm not sure if the graininess is the result of the scanner that Costco used or my film (Fuji 400) and the low light.)

  • \$\begingroup\$ [Off Topic] That f/1.7 is a very interesting aperture. Wonder why 1.7, and not 1.8 or 1.4. Seems like that would make it difficult to maintain reciprocal nature between shutter and aperture when using very wide apertures. \$\endgroup\$
    – jrista
    Commented Oct 28, 2010 at 19:42
  • \$\begingroup\$ @jrista: This looks like my lens: blogger-off.com/2010/04/… \$\endgroup\$
    – Mike Kelly
    Commented Oct 28, 2010 at 20:12
  • 1
    \$\begingroup\$ @jrista f/1.7 is a half stop between f/1.4 and f/2. If your shutter speeds are in half-stop increments, then it should be easy. \$\endgroup\$
    – Evan Krall
    Commented Oct 28, 2010 at 20:40
  • \$\begingroup\$ @Evan: Ah, its a half stop. I know the full stop and 1/3rd stop scale pretty well, but I don't really use half-stop much, and I have never used it below f/2.8, so I was confused by 1.7. Thanks for the clarification. \$\endgroup\$
    – jrista
    Commented Oct 28, 2010 at 21:53
  • 1
    \$\begingroup\$ @jrista Older 35 mm cameras (SLRs and rangefinders) typically came with primes in the 47-55 mm focal length range with maximum apertures a little less than f/2; f/1.9, f/1.8, and f/1.7 were all common. (For a premium you could get them in the f/1.2 - f/1.4 range too, of course, but that wasn't standard.) My first one, a Konica rangefinder, had a max of f/1.9. It also had detents at f/2 and up as usual in half-stop increments. I always figured that although f/1.9 wasn't really any different from f/2--it's 1/7 of a stop wider--it helped sell cameras ;-). \$\endgroup\$
    – whuber
    Commented Oct 29, 2010 at 1:55

3 Answers 3


I think you'll want to go with the 50mm f/1.7. Since you'll be shooting in low light without flash, you will want the fastest lens you can get.

Also, the 50mm is going to give you more natural looking shots, and the wider angle will allow you to capture the overall feel of trick-or-treating better.


Just nipped outside with my trusty light meter, and it suggested 0.6 seconds @ ISO 400 f/2.8 for a street lit road. So your f/1.7 lens is your best bet with no flash. Obviously, your street may be better lit, but you'll be looking about the 1/10 sec mark for exposure times which is "quite long" for kids/photographers to hold still for - maybe you could up light with a torch for that extra light, I mean, "spooky effect"?


I would suggest using the 50 1.7 - it is probably the most appropriate focal length for taking pictures of nearby kids, and will give you the most flexibility with shutter speed.

Replace your battery if there's any doubt about it - the last thing you want is to take a roll or two of pictures and discover that they're all black.

According to my favorite cheat sheet, streetlights average around exposure value 3. At f/1.7, ISO 400, you can expect shutter speeds around 1/10 of a second. However, you can expect that light to vary by a stop or two, so you might have to use 1/5 or 1/2.5.

1/10th of a second is pretty slow; you'll have a great deal of motion blur even when the kids aren't moving intentionally. A general guideline for handheld photography is 1/focal length, so 1/50 for that lens.

As f/1.7 is a very wide aperture and is realistically the widest you're going to find, I'd suggest doing something else to compensate for the low light: you can buy a higher-ISO film, or add light. Otherwise, you may be restricted to taking photos in well-lit areas.

  • \$\begingroup\$ I did replace my battery and my meter seemed to work; I'll have to see how they come out once I get them developed, though. Your cheat sheet matches with what I saw w/ my meter, though... At f/1.7, 400 ISO, I was able to manage at 1/60 in the better lit areas (my porch), and 1/30 in the poorer lit areas. \$\endgroup\$
    – Mike Kelly
    Commented Oct 29, 2010 at 19:05

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