Reciprocal Exposure: New to the site so I thought I'd throw one out to see what your replies might look like. I fully understand the reciprocal rule for exposure but was just thinking.

picabak

New to the site so I thought I'd throw one out to see what your replies might look like. I fully understand the reciprocal rule for exposure but was just thinking. If this is from the film era and applies to 35mm film, which is generally equivalent to the size of full frame sensors, I can see that it would be somewhat accurate for full size sensors. But does it also apply to the smaller APS-C sensors in the same relationship or should there be another 50% consideration applied? This is simple enough to experiment with but just testing the waters.

Searcher Loc: Kent, England

If you are talking of the minimum shutter speed required to prevent camera shake when hand holding then use the equivalent to full frame numbers. i.e. 300mm lens on a DX camera has an "equivalent" focal length of 450, the reciprocal being 1/450th sec. If you have very steady hands or image stabilisation you may be able to bring this down considerably.

GoofyNewfie Loc: Kansas City

Searcher wrote:

If you are talking of the minimum shutter speed required to prevent camera shake when hand holding then use the equivalent to full frame numbers. i.e. 300mm lens on a DX camera has an "equivalent" focal length of 450, the reciprocal being 1/450th sec. If you have very steady hands or image stabilisation you may be able to bring this down considerably.

:thumbup:

It's just a rule of thumb, but you do need to factor in the equivalent focal length.

OddJobber Loc: Portland, OR

Since the APS-C sensor is smaller, lenses can have a smaller diameter than FX lenses and still cover the sensor area with light. But the golden triangle is the same. f:4 at 1/100th is still the same regardless of sensor size. Shooting with 35mm film or medium format, the rules are the same.

lightchime Loc: Somewhere Over The Rainbow

Searcher wrote:

If you are talking of the minimum shutter speed required to prevent camera shake when hand holding then use the equivalent to full frame numbers. i.e. 300mm lens on a DX camera has an "equivalent" focal length of 450, the reciprocal being 1/450th sec. If you have very steady hands or image stabilisation you may be able to bring this down considerably.

I am not sure we are all on the same page. My thoughts of reciprocity relate to a long exposure of color film. Reciprocity breaks down and extra exposure is required.

"This reciprocity works well, up to a point, but film users will find that, when you have very long exposure times, several seconds or so, the reciprocity breaks down and extra exposure time is necessary to compensate. This is known as reciprocity failure."

Sorry, I don't know the source of the quote, but it is how I remember it from pre-digital days. If this is to what you are referring, it does not relate to digital - only film.

picabak

My post is relative to hand holding and the shortest shutter speed that would reasonably give acceptable blur. It seems there are different opinions so I'll add a bit more for discussion purposes. Since the field of view is what changes and the exposure triangle is not a main concern as a 100 mm lens @ f/4 remains a 100mm lens @ f/4, as far as the sensor in concerned, and its essentially an in camera cropping phenomenon, the question remains, is the rule the same for crop frame as for full frame?

OddJobber Loc: Portland, OR

Yes.

boberic Loc: Quiet Corner, Connecticut. Ex long Islander

picabak wrote:

My post is relative to hand holding and the shorte... (show quote)

A lot depends upon how steady your hands are. A long long time ago (reminds me of American Pie) when I was much younger I could easily hand hold a 200mm lens at 1/50. Now, I have to use shutter priorty to make sure I don't have cameraa shake. But nobody can hand hold a 400mm at 1/100.

GoofyNewfie Loc: Kansas City

picabak wrote:

the question remains, is the rule the same for crop frame as for full frame?

No, but the APS-C sensored camera is not that different so the results are pretty close.

To take this down to an extreme example (point & shoot camera level) with the Canon Powershot A10, at an actual 15mm you get a full frame equivalent of about 100mm. Do you seriously think you could hand-hold a camera that has the same angle of view as a 100mm on a full-frame at 1/15th sec and get a blur-free photo? I doubt it.
So you really should factor the sensor size into the equation.

That being said, most cameras/lenses these days have image stabilization.

SonyA580 Loc: FL in the winter & MN in the summer

I don't think the size of the sensor has anything to do with it. That would be like saying it differs between 35mm, 4x6 and 8x10 film. The reciprocal rule applies to the inverse relationship between aperture and time of exposure. If it's out of whack on film, it will be the same on a digital sensor too ......, I would think.

Check this out:

http://www.picturecorrect.com/tips/understanding-reciprocity-in-photography/

picabak

OK, I've got my answers to the initial post. Yes, no, and a couple that should not have replied at all. Thanks for everyone's inputs.

GoofyNewfie Loc: Kansas City

picabak wrote:

OK, I've got my answers to the initial post. Yes, no, and a couple that should not have replied at all. Thanks for everyone's inputs.

That's pretty much par for the course around here.
The confusion was probably the way the question was asked.
Reciprocity is a similar-sounding but very different issue than holding a camera steady.
Thanks for not titling your post "Help" or "Advice needed" (or incorrectly "Advise needed" ) which happens too often here.

Welcome to the hog!

Crwiwy Loc: Devon UK

For those who were confused - or too young to remember film -

I belive the poster was referring to when you have very long exposure times, several seconds or so, the reciprocity breaks down and extra exposure time is necessary to compensate. This is known as reciprocity failure.

http://www.geofflawrence.com/reciprocity_failure.html

ocbeyer Loc: Baltimore

OddJobber wrote:

Since the APS-C sensor is smaller, lenses can have a smaller diameter than FX lenses and still cover the sensor area with light. But the golden triangle is the same. f:4 at 1/100th is still the same regardless of sensor size. Shooting with 35mm film or medium format, the rules are the same.

:thumbup: :thumbup:

jerryc41 Loc: Catskill Mts of NY

lightchime wrote:

I am not sure we are all on the same page. My thoughts of reciprocity relate to a long exposure of color film. Reciprocity breaks down and extra exposure is required.

That's what I thought at first - reciprocity failure. But mentioning the sensor size makes me think it's about shutter speed.