Rule Of Thumb

Discussion in 'Exposure Discussion' started by hoffy, Jul 18, 2010.

  1. hoffy

    hoffy Member

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    Howdy all,

    When I first took up photography, I was always told a quick rule of thumb dealing with shutter speed and camera shake, for 35mm.

    "If you were to set the minimum shutter speed to be the same as the focal length, you shouldn't be effected by camera shake"

    So, if I had a 50mm lens on, I should be able to readily hand hold @ 1/50th. For me, I have generally found this works quite well (OK, I can probably hand hold a bit slower). Do others use this rule, or is it total bunk. If others do, how would you apply this to say, 6x7 Medium Format?

    Cheers
     
  2. Jeff Kubach

    Jeff Kubach Member

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    On my Rolleiflex I can hand held it down to 1/30. On my RB67 I always use a tripod no matter what speed.

    Jeff
     
  3. Ian Grant

    Ian Grant Subscriber

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    It's a reasonable rule of thumb. But only applies to 35mm., but if you think of the equivalent FL then it's good for medium format, 54 etc.

    My preferred speed is 100th (old Compur) when shooting hand held.

    Ian
     
  4. Mike Richards

    Mike Richards Member

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    SLR or RF?

    The rule of thumb works well for SLRs, if I'm careful. There's always that mirror slap that becomes a limiting factor. With a rangefinder or other mirror-less camera, I can usually go one stop slower, again if I'm careful.
     
  5. hoshisato

    hoshisato Member

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    This rule is a good reminder for me to make sure to pay attention to the actual focal length on a zoom lens when shooting handheld if the light starts to fail a little.
     
  6. RalphLambrecht

    RalphLambrecht Subscriber

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    As Ian said, this is a 35mm rule of thumb, and it works for images when sharpness is not critical. But, to get the highest resolution possible, the use of a tripod is essential, and the rule-of-thumb, requiring nothing less than the reciprocal of the focal length as the maximum exposure time, is inadequate. Attached is an enlarged picture sequence showing, from left to right, the results of photographing a point light source, at a distance of 5 m, with a handheld 50mm lens, at 1/60, 1/125, 1/250 and 1/500 of a second. The suggested time of 1/60 s is far from adequate. It took as little as 1/500 s to eliminate camera shake completely. But, the tripod-mounted camera delivered a perfect result at 1/60 of a second.
     

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  7. Mike Richards

    Mike Richards Member

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    Ralph, well said and demonstrated. The rule of thumb is exactly that, and provides only a guide for reasonably acceptable sharpness under difficult lighting conditions.
     
  8. hoffy

    hoffy Member

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    Very interesting! Putting that into context, how enlarged is that shot? Also, the shot that was done on the tripod, was Mirror Lock Up used? You have me very curious!
     
  9. Q.G.

    Q.G. Inactive

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    Not so.
    Hand shake is always much worse. What mirror slap would do always disappears completely in that.

    Now if you would mount a camera on a tripod you could start worrying about flapping mirror.
    But never handheld.

    Ralph, did you use mirror prerelease or lock-up in your test?
     
  10. Q.G.

    Q.G. Inactive

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    The rule of thumb is a good rule, expressing the relation between focal length and the magnification of shake.
    But it's not just the focal length you need to keep an eye on when deciding what speed to use. The condition of the support (i.e. you) plays just as large a roll.
    Just after cycling up Mont Ventoux, even a very fit athlete will have trouble holding a camera steady at the fastest shutterspeeds. Even more so if that mountain lives up to the popular explanation of its name and there is a stiff breeze blowing that athlete about.
    That sort of thing.
     
  11. RalphLambrecht

    RalphLambrecht Subscriber

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    The 'length' of the first camera shake on the left is about 2.5x the standard CoC for the 35mm negative format (2.5 x 0.022 mm). In other words, your resolution is dropping to about 18 lp/mm. That's pretty poor.

    No mirror lock-up was used in order to compare to the worst tripod performance possible. Even with mirror slap, the tripod performance is about the same as the CoC. This proves Q.C.'s statement that mirror slap is minor compared to hand-held camera shake.
     
  12. RalphLambrecht

    RalphLambrecht Subscriber

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    After thinking about it a bit more, I'm not so sure that it really is a 35mm rule. I remember my Dad teaching me this rule at a time when we used nothing but medium-format cameras. Could it be that the rule is an older medium-format rule of thumb and was carelessly carried over to 35mm?

    The smaller the format, the more critical camera shake is.

    The attached sample shows the 1/60s exposure with a 50mm lens again. This time it also shows the standard CoCs for 35mm, 6x6 and 4x5. Judging from this shot, I'd say that 35mm needs a tripod or a faster shutter speed, but MF would get away with the rule of thumb. LF has no issue at all, but a 50mm lens is unrealistic for LF.
     

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  13. markbarendt

    markbarendt Subscriber

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    I think this is a marginal as a rule-of-thumb and only applicable where there is nothing else driving the shutter speed choice and when the value of the shot is low.

    As with most rules-of-thumb, it is like a set of training wheels and absolutely conditional on the shooters skill and intent of the photographer.

    For a high value shot, shutter speed needs to be driven by an answer to this question "what do you, as the artist or technician, expect from this photo?"

    Given that the "intent" may change from shot to shot the rule-of-thumb is in my estimation bunk for serious work.

    For example:

    I've been shooting a fair amount lately at 1/10th to 1/15th hand-held and panning. The rule of thumb is just way to fast for the effect I want.

    For general snap shooting I'd rather deal with a little underexposure when I'm enlarging, than with unintended blur so the rule-of-thumb, based on my preferences, is too slow for me there.

    If I really need a truly sharp shot I'm going to use something besides a rule-of-thumb and I'll be lugging the right tools along.
     
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  15. Q.G.

    Q.G. Inactive

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    Don't make too big a deal out of it. This rule of thumb is no more than a way to find a safe handheld shutterspeed.
    As such (and for what's it's worth) it stands, no matter what other considerations there are that drive shutterspeed choice.
    :wink:
     
  16. Paul VanAudenhove

    Paul VanAudenhove Member

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    Maybe I haven't had enough time to wake up on a Sunday morning yet, but instead of saying "If you were to set the minimum shutter speed to be the same as the focal length, you shouldn't be affected by camera shake" wouldn't phrasing it to read "If you don't set the shutter speed to be at least the same as the focal length, you will be affected by camera shake" make more sense?
     
  17. Ian Grant

    Ian Grant Subscriber

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    No it doesn't make any more sense, have a coffee wake up :D

    It's entirely possible to get sharp images at slower speeds, just less likely, and there's to many variables. It depends how you're standing, holding the camera, type of cameras etc.

    When shooting with my Leica + 50mm lens I know that using 125th of a second I always get good sharp shots, there's no mirror to bounce.

    It's just a very loose rule of thumb, no more than that.

    Ian
     
  18. mopar_guy

    mopar_guy Subscriber

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    Another factor to consider is the degree of enlargement expected.

    For example, consider a 4x5 press camera such as a Speed Graphic. To get a print that is 8x10 you only enlarge 2X.

    From 6x7, the same size print is 4X enlargement and a 35mm would need a 8x enlargement. Camera shake from the 35mm would be more exaggerated.
     
  19. Steve Smith

    Steve Smith Subscriber

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    The film is just an intermediate stage though and is irrelevant. What does matter is the final print size and the larger the print (or magnification) the greater the chance of camera shake being visible in the print.

    Obviously we can then start arguing about viewing distances!.....


    Steve.
     
  20. RalphLambrecht

    RalphLambrecht Subscriber

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    Since the final print size is typically unknown, or could change in the future, it is common to make sure that camera shake is below the CoC. That's why I used it as a criterion in my posts.
     
  21. Sirius Glass

    Sirius Glass Subscriber

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    The really interesting point is that your father taught you this for MF. Historically, the rule of thumb was developed [pun intended] for MF and then in the 1960's and 1970's at the photo stores I worked at*, we started telling the customers to use the rule for 35mm cameras.

    Steve


    * one was Baker's Photo on Wisconsin Avenue Washington DC NW
     
  22. RalphLambrecht

    RalphLambrecht Subscriber

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    That's what I thought. Thanks for setting that straight.

    As the attachment in post #12 shows, moving the rule from MF to 35mm was a leap of faith, but, as others have pointed out, it's just a rule of thumb anyway. For optimal resolution, a good tripod and solid ground are essential.
     
  23. keithwms

    keithwms Member

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    I think the 1/FL rule works fairly well, but mostly in the long FL extreme. For wide lenses I feel that I can go much longer than 1/FL.

    For medium format, I would suggest thinking in terms of field of view. For 35mm, the FL=FOV in degrees, approximately. You get something like 50 degrees diagonal angle for a 50mm lens. But for MF and LF the FOV is much bigger, of course.

    A 50mm lens on 6x6cm square gives a field of view of ~80 degrees i.e. superwide. With a superwide on a medium format rangefinder I find that I get acceptable sharpness at ~1/8 sec, and even further with good bracing.

    In the end, it's all very individual. Technique matters for sure. How much you enlarge matters to, of course. But overall, I very seldom think of 1/FL when shooting- the timing of the scene usually decides my exposure. When I was doing sports and birds etc. with 35mm I thought of 1/FL more often.
     
  24. Sirius Glass

    Sirius Glass Subscriber

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    FOV Comparisions:
    For 35mm which I know the FOV well I use the translation for MF. For example for 6x6 80mm is normal, so 150mm , which is about double, would be like a 100mm in 35mm. 250mm MF is about three times 80 so that is equivalent to a 150mm in 35mm.

    For large format, 4x5, I take the focal length and divide by three so a 150mm is approximately a 50mm lens in 35mm; 127mm to 135mm 4x5 is approximately like a 30mm to 32mm in 35mm. Thus a 270mm is roughly like a 90mm lens in 35mm.

    Steve
     
  25. Mainecoonmaniac

    Mainecoonmaniac Subscriber

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    Don't forget the caffeine factor and other movement

    I notice that if I have too much coffee, my hands aren't as steady. When I hand hold a camera with slow shutter speeds, I take deep breath, exhale then gently squeeze the shutter. I carry a Gorillapod in my camera bag. It's such a versatile tripod, the tripod can be rested on or wrapped around. Along with a tripod, mirror lockup and a shutter release helps too.
     
  26. jeffreyg

    jeffreyg Subscriber

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    I agree with Ralph always use a tripod or some other way to steady the camera whenever possible. Since some thumbs are steadier than others their rules sometimes don't work.