Go Back   Steve's Digicams Forums > Digicam Help > Newbie Help

Reply
 
Thread Tools Search this Thread
Old Mar 1, 2010, 7:45 AM   #11
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,572
Default

I just did some research. In common use, the 'Rule of Reciprocity' is also referred to as 'The Golden Rule'. That is, "Do unto others as you would have others do unto you" or words to that effect.

In photography, the 'Rule of Reciprocity' seems to be related to exposure settings. That is, if you open the aperture by one stop, you must halve the exposure time to preserve the same exposure value.

I can't find any instance of the "shutter speed = 1 / focal length" being referred to as the 'Rule of Reciprocity'. Does anybody else have any idea how this term came into use for that?
__________________
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.
TCav is offline   Reply With Quote
Old Mar 1, 2010, 9:35 AM   #12
Super Moderator
 
peripatetic's Avatar
 
Join Date: Nov 2004
Posts: 3,599
Default

I have never heard it referred to that way in any photographic manuals or good websites.

Except of course that dividing a number into 1 is also known as taking the reciprocal (multiplicative inverse), so perhaps in some colloquial usage at a camera club or similar it might have been referred to that way and the OP picked it up.

I have heard frequent mention of "reciprocity" in photography, and of course "reciprocity failure" as it applies to long film exposures.

http://en.wikipedia.org/wiki/Reciprocity_failure

Possibly the OP has confused "reciprocity" and "the focal length reciprocal".
__________________
My gallery
My X100 blog

Last edited by peripatetic; Mar 1, 2010 at 9:38 AM.
peripatetic is offline   Reply With Quote
Old Mar 1, 2010, 9:45 AM   #13
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,572
Default

Perhaps, but it's appeared here multiple times, so I wouldn't pin it on any single person. But I think they may have all read the same thing somewhere else, and in that content, "Reciprocity" and "Reciprocal" get confused.
__________________
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.
TCav is offline   Reply With Quote
Old May 10, 2010, 3:47 AM   #14
Senior Member
 
RioRico's Avatar
 
Join Date: Aug 2008
Location: In mountainous California or Arizona or Guatemala or somewhere.
Posts: 224
Default

'Reciprocity' in photography usually refers to reciprocity failure, a characteristic of film emulsions in long exposures. The handheld 1/F guideline isn't reciprosity, and isn't even a very good rule-of-thumb.

In THE CAMERA, Ansel Adams writes of handholding a 35mm film camera with a 50mm prime lens in daylight, shooting at various speeds including 1/50 sec (the 1/F rule of thumb), but not getting a SHARP image until he shot at 1/250 sec or faster. That's an extra 2+ stops than the 1/F guideline. And that's with an FF camera. With an APS-C sensor in an unstabilized camera, you need yet another stop. A handheld camera with a 50mm lens? Shoot at 1/500 sec.

The SR (Shake Reduction) on my Pentax K20D gives me about 3 stops advantage all the way out to 300mm or so. So I can use the 1/F rule, no problem. Without SR or IS (image stabilization) you need a fast shutter.

For maximum sharpness, besides a fast shutter, you need to consider the aperture and the diffraction limit. If you're a pixel peeper, you may see sharpness decreasing above f/9 or so; beyond that, diffraction cuts in. Whether or not this matters is an individual thing. For shooting stationary things and scapes etc, you'll probably want maximum sharpness. A tripod may be necessary. For shooting people, whether still or in motion, you can get away with much more softness, unless you want every facial crag and scar on your subject to stand out.

Shooters brag of using longish lenses and slow shutters. For people and features, that's fine. For detail, use a fast shutter or a tripod.
RioRico is offline   Reply With Quote
Old May 10, 2010, 5:57 AM   #15
Super Moderator
 
Mark1616's Avatar
 
Join Date: Oct 2005
Posts: 7,452
Default

It is very much down to user technique, with a bad technique and as we get older and are not as stable as we used to be (I notice more shake now) then we need higher shutter speeds. The better we can brace the easier it is to shoot at lower speeds. Stabbing at the shutter will cause problems, being too tense will induce wobble etc etc.

I just tried shooting with the 7D and Canon 85mm f1.8 (35mm FL equivalent of 136mm) to see what I was getting. Down to 1/100s I had no real issues, but lower and blur was common in many shots. It is easy to eradicate this even without IS at lower speeds and that it to shoot a burst of 3, usually the middle one for me is still tack sharp as I've fully completed the shutter press and I'm not yet coming off. Doing this I was fine for the middle shot at 1/60s.

If you start introducing external factors like wind etc then there will be a call to use a higher shutter speed, also for safety, to ensure that you are solid every time then going faster than the rule of thumb is advised.
__________________
[SIZE=1][SIZE=2]Any problems with a post or thread please use the report button at the bottom left of the post and the team will help sort it out.
Mark1616 is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 8:43 AM.