Reciprocal rule for medium format

Patrick Robert James · Aug 27, 2017

wiltw said:
As has already been made clear, "Rule of Thumb - which is a guideline and nothing more."

Rule of thumb
From Wikipedia, the free encyclopedia

A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination. It is based not on theory but on practical experience.

The title of the thread is "Reciprocal rule for medium format" not "Reciprocal rule of thumb..." but thanks for english-splaining for me, especially with the big bold letters. Maybe next time use big alphabet blocks so I can understand more better. Lol.

wiltw · Aug 27, 2017

Patrick Robert James said:
The title of the thread is "Reciprocal rule for medium format" not "Reciprocal rule of thumb..." but thanks for english-splaining for me, especially with the big bold letters. Maybe next time use big alphabet blocks so I can understand more better. Lol.

It is a Rule of Thumb, it has never been a Rule: 1/ FL

wiltw · Sep 10, 2017

I was thumbing thru some old copies of Modern Photography, and in Sept 1964 some testing was done using a Leica M3 with 90mm lens. The same camera and lens was put into the hands of a number of photographers, who all were given the challenge of hand holding the camera as steady as possible. When the 90mm lens was shot at 1/60, 27% of the images were judged to be unsharp; with a 90mm lens at 1/125 about 14% were unsharp.

using the 1/FL rule of thumb for 'reasonable handholding' that most folks use, one would ues 1/90 and one shot of 5 would be unacceptably sharp, and even at 1/125 nearly 1 out of 6 shots would be unacceptably sharp.

IF the rule of thumb had been properly adjusted for 135 as I mentioned in post 11, the rule would instead be

135 format = 1/(FL* 2.3)

and at 1/200 almost all shots would be acceptably sharp (although testing did not include any speeds above 1/125)!

RichardJack · Sep 11, 2017

Forget the rules! There are many factors not taken in by the old rules. People are not equally steady, the ground is not always level, there could be wind, and so on.

Play it safe and once your over 100mm regardless of format use the highest shutter speed possible or a tripod or monopod. This is where it's an advantage to have several backs with various ISO films or several camera bodies.

When I shoot 6x7 I use 1/500 for my 150-250mm ( 250mm is risky), over 250mm it's tripod time. Brace yourself whenever possible.

Svenedin · Sep 11, 2017

I know that I shake a bit, I cannot help it so I try to use a minimum of the "reciprocal rule" + 1 shutter speed faster if possible. If not possible I will still have a go and accept that the picture may or may not turn out well. If there is anything available to help me keep steady I will use it. I tend to use faster film if the light is not good for the very reason of keeping shutter speed up.

Sirius Glass · Sep 11, 2017

The only time I get in trouble with this rule is when I have violated it. Not every time, but enough times to use a tripod or setting the camera down instead.

faberryman · Sep 11, 2017

It is a rule of thumb, not a rule. You should be able to look at your negatives to see what shutter speed you need to use for sharp images.

NJH · Sep 11, 2017

Honestly IMHE there are useful minimum speeds to work from with certain cameras under certain conditions that are more important than the 1/FL rule or variations on it. Stuff like being able to get lower speeds to produce good results handheld when one is propped against something solid, you hold the camera tight into the body and use controlled breathing like a marksman etc. as opposed to run and gun when you know you need a fast speed to get decent results (unless blurring is an intentional effect). For me this gives me a range in general from 1/30 to 1/250 with 1/125 a typical crossing point where subject movement has to be considered. This sort of thing I do recall or think about much more than 1/FL to be honest. If I compare negs from my Rollei 6008 and Leica M6 I don't see much difference in these terms surprisingly and I do tend to bump up speeds a touch when moving into tele range on each system but don't tend to go for lower speeds for wide angles (DoF is much bigger anyway so often its not like one is gaining a lot from much slower speeds).

An interesting question perhaps, how many cameras follow this 1/FL rule or similar when in program or fully auto mode?

RichardJack · Sep 12, 2017

The reality is when you look closely at your negatives under magnification and see a blur It's too late! Common sense and honesty (you know if you shake or not) is the only rule. Don't take chances with subjects that you can't reshoot.

Cameras with Program modes started using 1/FL or higher since the late 1970's, I'm pretty sure the Minolta XD-11, Canon AE1 program, Pentax all had that covered, Nikon's FA didn't come along until about 1983. I don't think this question applies to MF. MF metering if any was usually aperture priority and you had better pay attention to the speed it was giving you. The problem has always been the slow ISO's of film. I loved slow films and it was difficult shooting at f5.6-8 all of the time, the lighting just didn't permit it. I'm guilty of taking my shutter speed too low. I am very steady and could often get away with 1/15 with a 50mm or 1/30 with my 80mm in MF. Proofs and small prints looked fine. Once I started scanning at 4000dpi and viewing at 100% I could see that what I thought was sharp was not sharp at all. Did my customers care, usually not.

Sirius Glass · Sep 12, 2017

I have used the advice of the reciprocal rule and never had a problem with using any speed film. The "trick" is to know when to use a tripod because the shutter speed is too slow for hand holding.

Poisson Du Jour · Sep 12, 2017

faberryman said:
It is a rule of thumb, not a rule. You should be able to look at your negatives to see what shutter speed you need to use for sharp images.

This should be decided at the time of exposure, considering the scene and its elements and the Tv / Av needed to achieve the result you are looking for, there and then..
Looking at a dud negative afterwards and making a cursory deliberation as to what happened is like closing the stable door after the horse has bolted.

msage · Sep 13, 2017

I always use a tripod with MF!

jim10219 · Sep 13, 2017

So, theoretically speaking, if you wanted to apply that same rule of thumb to MF, then you'd use the same formula. The size of the negative has no impact on the theory behind that rule. The size of the grain might, as would the size of the enlarged print, and your tolerance for sharpness. But the fact that the equivalent focal length of a lens on MF is different from 35mm doesn't change the relationship between camera shake, focal length, and exposure time. The rule changes with digital crop sensors and stuff because you're keeping the size of the sensor the same, but changing the resolution of the sensor, thus making it more or less sensitive to that relationship. Much like changing the grain size of the film. Camera shake would be less of an issue with a grainy film like Ilford Delta 3200 than with a fine grained film like Fuji Velvia 50 with all other camera settings being equal, due to the fact that there are less particles per square inch to resolve detail.

And that's why I don't like this "rule of thumb". It doesn't do a good job of taking into account all of the variables at play. It just throws some easy to remember numbers together to give you a false sense of security. Follow it at your own risk.

Sirius Glass · Sep 13, 2017

msage said:
I always use a tripod with MF!

I almost never use a tripod with MF with the exception of the 500mm f/8 Hasselblad lens which is too heavy to hold steady.

Sirius Glass · Sep 13, 2017

jim10219 said:
So, theoretically speaking, if you wanted to apply that same rule of thumb to MF, then you'd use the same formula. The size of the negative has no impact on the theory behind that rule. The size of the grain might, as would the size of the enlarged print, and your tolerance for sharpness. But the fact that the equivalent focal length of a lens on MF is different from 35mm doesn't change the relationship between camera shake, focal length, and exposure time. The rule changes with digital crop sensors and stuff because you're keeping the size of the sensor the same, but changing the resolution of the sensor, thus making it more or less sensitive to that relationship. Much like changing the grain size of the film. Camera shake would be less of an issue with a grainy film like Ilford Delta 3200 than with a fine grained film like Fuji Velvia 50 with all other camera settings being equal, due to the fact that there are less particles per square inch to resolve detail.

And that's why I don't like this "rule of thumb". It doesn't do a good job of taking into account all of the variables at play. It just throws some easy to remember numbers together to give you a false sense of security. Follow it at your own risk.

Shaking moves the image covering more area than any grain.

wiltw · Sep 13, 2017

jim10219 said:
The rule changes with digital crop sensors and stuff because you're keeping the size of the sensor the same, but changing the resolution of the sensor, thus making it more or less sensitive to that relationship. Much like changing the grain size of the film. Camera shake would be less of an issue with a grainy film like Ilford Delta 3200 than with a fine grained film like Fuji Velvia 50 with all other camera settings being equal, due to the fact that there are less particles per square inch to resolve detail..

Waitasec... it is commonly accepted that the FF size dSLR uses 1/FL rule of thumb, while APS-C size dSLR uses 1/(FL*1.6) as its rule of thumb!
FF sensor height is 24mm, while APS-C is about 15mm 15/24 = 0.625 and 1/1.6 = 0.625, and the same FL on both provides AOV with [50mm on APS-C] is like AOV of [80mm on FF]. So 80mm lens on FF sees same linear measurement as 50mm on APS-C -- with the shake being the same fractional proportion of the angle of view of the frame when using 1/80 sec on both.

piu58 · Sep 15, 2017

> The size of the negative has no impact on the theory behind that rule.

Hmm. MF cameras are in average heavier than 35 mm cameras. A heavier camera gets more stable simply from inertia.

jerrybro · Sep 15, 2017

piu58 said:
> The size of the negative has no impact on the theory behind that rule.

Hmm. MF cameras are in average heavier than 35 mm cameras. A heavier camera gets more stable simply from inertia.

The mirror mechanism is also larger meaning the mass of the camera would have to have to be larger to compensate for the movement. I use a tripod whenever I can, it always improves the image quality, regardless of the film format. I remember taking a shot with a Leica M4 and 50 Summicron on a heavy tripod and was stunned at the difference it made in sharpness. YMMV of course.

jim10219 · Sep 15, 2017

wiltw said:
Waitasec... it is commonly accepted that the FF size dSLR uses 1/FL rule of thumb, while APS-C size dSLR uses 1/(FL*1.6) as its rule of thumb!
FF sensor height is 24mm, while APS-C is about 15mm 15/24 = 0.625 and 1/1.6 = 0.625, and the same FL on both provides AOV with [50mm on APS-C] is like AOV of [80mm on FF]. So 80mm lens on FF sees same linear measurement as 50mm on APS-C -- with the shake being the same fractional proportion of the angle of view of the frame when using 1/80 sec on both.

Yeah, but if the megapixel count is the same on both sensors, then your packing them in more tightly on the smaller APS-C. So it's more sensitive to shake than the full frame. I'm assuming that the whole point of using a larger film size, finer grain, or higher pixel count camera is to get more detail.

And this is why I hate that rule. It makes too many assumptions about resolution, what you're planning to do with the photograph, and the gear you're using. It doesn't even define what sharpness is! "Sharpness" is not a yes or no question. Angle of view is one thing, and it's definitely part of the equation. But it's no where near the only factor to consider. You can get away with a lot more shake if you're just posting a thumbnail on the internet than if your printing a 32x48 photo.

Some rules are made to be broken. This rule was made to be forgotten.

Reciprocal rule for medium format

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