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01-29-2021, 04:29 AM   #1
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Reciprocal rule and crop sensors

My understanding is a 50mm is always a 50mm. A crop sensor doesn't magnify, it simply captures less of the scene. I was reading an article in Amateur Photographer in which the author stated you needed to include crop factor multiplication when calculating a reciprocal shutter speed (50mm/ 1/50, 200mm/ 1/200 etc). I think he is wrong, but I am no expert. My understanding (as stated above) is as a 105mm is always a 105mm, irrespective of the sensor, the reciprocal shutter speed shouldn't change either (1/105+). So, am I wrong, again? lol

This ties in with my previous thread but I didn't want the question lost in one that isn't active.

01-29-2021, 04:55 AM - 6 Likes   #2
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yet another rule I keep ignoring.....
01-29-2021, 05:32 AM - 3 Likes   #3
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The reciprocal rule isn't based on the focal length of the lens but the narrowing of the angle of view. The narrower an angle of view becomes the more camera shake is noticeable. So with a crop sensor being smaller narrowing the angle of view captured vs a wider angle of a full frame sensor using the same lens the shutter speed needs to increase respectively using the effective focal length.

Now with that said this applied very well in the days digital cameras either had no shake reduction or the shake reduction systems at the time, with the exception of one camera mfg. Olympus had a 4 axis shake reduction years before anyone else. So at the time many systems weren't as effective as they are today so the rule still applied as a means of preventing shake. With todays shake reductions it isn't needed to be used unless one has their reduction system turned off or certain situations where the shutter speeds being used render the shake reduction system ineffective.

Last edited by Oldbayrunner; 01-29-2021 at 05:37 AM.
01-29-2021, 05:39 AM   #4
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QuoteOriginally posted by Oldbayrunner Quote
The reciprocal rule isn't based on the focal length of the lens but the narrowing of the angle of view. The narrower an angle of view becomes the more camera shake is noticeable. So with a crop sensor being smaller narrowing the angle of view captured vs a wider angle of a full frame sensor using the same lens the shutter speed needs to increase respectively using the effective focal length.

Now with that said this applied very well in the days digital cameras either had no shake reduction or the shake reduction systems at the time, with the exception of one camera mfg. many systems weren't as effective as they are today. With todays shake reductions it isn't needed to be used unless one has their reduction system turned off or certain situations where the shutter speeds being used render the shake reduction system ineffective.

Aaaaaaaaaah thanks for this. Now this is a prime example of why I ask

01-29-2021, 05:42 AM - 2 Likes   #5
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The difference is how far away you are when you use the lens. To capture a scene with fullframe i may be 10 meters away. With an apsc sensor and the same lens I need to be 15 meters away to capture that scene. If you shake 1 at 10m the camera arc is 0.17m at 15m it is 0.26m so you need less shake with the apsc or a faster shutter.
01-29-2021, 05:53 AM   #6
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QuoteOriginally posted by swanlefitte Quote
The difference is how far away you are when you use the lens. To capture a scene with fullframe i may be 10 meters away. With an apsc sensor and the same lens I need to be 15 meters away to capture that scene. If you shake 1 at 10m the camera arc is 0.17m at 15m it is 0.26m so you need less shake with the apsc or a faster shutter.
Thanks. I was working on the principle, using the above setups, that with each camera I would be the same distance from the target. The image would lose the outer details but the subject would be the same size and require the same level of stabilization. All this science makes my brain hurt!
01-29-2021, 06:45 AM - 1 Like   #7
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For the same camera to subject distance, any object recorded on the sensor will suffer the same amount of hand-held camera shake blur on aps-c format versus FF format.

But the narrower field of view of the aps-c image means that when viewed on a screen or printed, the image will have been enlarged more than the FF one. Therefore any camera shake blur will be more noticeable. This is why the recommendation was to use a faster shutter speed than the 1/FL rule suggested.

As pointed out above, SR makes this less important than during the early days of aps-c DSLR cameras
01-29-2021, 07:25 AM - 5 Likes   #8
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Given that I've often shot 100mm at 1/8s hand held, and my hands are relatively unstable... does this mean anything with shake reduction? my concern these days is with subject motion blur and keeping my ISO low for less nice loss of resolution.

Here ya go, 95mm 1/6s hand held. Do you want the image or do you want to hang onto irrelevant practices from the last century.



01-29-2021, 07:30 AM - 5 Likes   #9
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Added to the confusion is if you are a pixel-peeper (that curse of the digital era), then the blur isn't relative to the frame but relative to the pixel size. For pixel peepers, the format size doesn't directly affect the rule, only the sensor pixel size.

A K-1 and a K-5 (both having pixels about 5 microns across) would use the same rule but a K-3 and a 50 MPix FF camera (4 micron pixels) would need 1.2X faster shutter speeds to avoid pixel-level blur.

But as others have said, this is only a guideline It really depends on how stable you are in holding the camera still. I'd wager that photographers that shoot zombie-style (with the camera held out at arms length to see the back panel display) have to use much faster shutter speeds to avoid blur than photographers who hold the camera against their face with the left hand supporting the lens and both arms braced on their body.
01-29-2021, 07:40 AM   #10
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QuoteOriginally posted by photoptimist Quote
... It really depends on how stable you are in holding the camera still. I'd wager that photographers that shoot zombie-style (with the camera held out at arms length to see the back panel display) have to use much faster shutter speeds to avoid blur than photographers who hold the camera against their face with the left hand supporting the lens and both arms braced on their body.
Good point, one I hadn't thought of. I do see a fair number of photographers with newer cameras handheld setting up shots via the rear display. Slap a heavy lens on there too and even shake reduction may not be enough.
Three points of contact is always best practice IMO.
01-29-2021, 07:47 AM   #11
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QuoteOriginally posted by photoptimist Quote
Added to the confusion is if you are a pixel-peeper (that curse of the digital era), then the blur isn't relative to the frame but relative to the pixel size. For pixel peepers, the format size doesn't directly affect the rule, only the sensor pixel size.

A K-1 and a K-5 (both having pixels about 5 microns across) would use the same rule but a K-3 and a 50 MPix FF camera (4 micron pixels) would need 1.2X faster shutter speeds to avoid pixel-level blur.

But as others have said, this is only a guideline It really depends on how stable you are in holding the camera still. I'd wager that photographers that shoot zombie-style (with the camera held out at arms length to see the back panel display) have to use much faster shutter speeds to avoid blur than photographers who hold the camera against their face with the left hand supporting the lens and both arms braced on their body.
Not to mention that I have days when I just don't care to deal with camera at arms length. I often like working with my ZS100, but not every day.
01-29-2021, 07:54 AM   #12
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QuoteOriginally posted by normhead Quote
Given that I've often shot 100mm at 1/8s hand held, and my hands are relatively unstable... does this mean anything with shake reduction? my concern these days is with subject motion blur and keeping my ISO low for less nice loss of resolution.
I don't think your hands are as shaky as you seem to think they are. That's quite excellent!
01-29-2021, 07:57 AM - 1 Like   #13
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QuoteOriginally posted by Kozlok Quote
I don't think your hands are as shaky as you seem to think they are. That's quite excellent!
Because of my hands I prefer heavier cameras. On my ZS100 I frequently have images ruined by motion blur even with SR and ordinary settings. With a K-1 or k-3 in my hands, I'm not so bad. Still when it comes up for discussion I've noticed, there are folks who can be a stop better than I am. I prefer max. of 1/8 second, some guys can consistently hold 1/4s.

Shooting film I'd always look for a tree or other solid object to brace on. I still do, old habits die hard. When driving through the park in snow season and stopping for an image, road salt sure makes a mess of my coats when I brace on my car.

Last edited by normhead; 01-29-2021 at 08:10 AM.
01-29-2021, 08:24 AM   #14
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In the film days, my understanding was that you used the reciprocal of the focal length to work out the slowest speed that would give you an acceptable result.

To get a good result, you'd use the next fastest speed. I still practise the technique of pressing the release gently, even though the camera has Shake Reduction.
01-29-2021, 08:38 AM - 3 Likes   #15
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QuoteOriginally posted by Robot camera Quote
In the film days, my understanding was that you used the reciprocal of the focal length to work out the slowest speed that would give you an acceptable result.

To get a good result, you'd use the next fastest speed. I still practise the technique of pressing the release gently, even though the camera has Shake Reduction.
Even with SR, you can't afford to be sloppy. I'm convinced SR works better for guys with residual film shooting habits, than it does for newbies. SO many times being unable to reverse habits is seen a a negative. Learning to brace for film and doing it without thinking shooting with SR definitely produces superior results.
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