hand held shutter speed

[petiot]

i found this test (http://www.enginova.com/Minimum%20Shutter%20Speed.htm) made by a quite good engineer i guess (;)).
I think that clearly shows that modern camera need a bit more concentration to ge the most of them when hand held .... maybe a cybernetic arm !!

Dan

[Roger_Cavanagh]

Dan,

Is this link correct? I got a not found error, even on enginova.com.

Regards,

Roger

[CyberDyneSystems]

Minimum Shutter Speed – Revised!

By Doug Criner

For a handheld 35mm camera, the conventional rule of thumb is to select a shutter speed of at least the reciprocal of the lens’ focal length to avoid blurring due to camera shake. For example, with a "normal" 50mm lens, the shutter speed should be no slower than 1/50th of a second.

The basis of this rule of thumb is seldom discussed, inviting the question whether it is, in fact, correct. I have conducted experiments that indicate that although the reciprocal-of-focal-length rule may be adequate for small enlargements, sharpness can be increased with significantly faster shutter speeds. Indeed, buried within one of Ansel Adam's books, he suggests that with a normal lens and a handheld camera, a shutter speed of anything less than 1/250th second may produce less than a completely sharp image. (See The Camera, Little, Brown and Company, 1980, p. 116.)

How steady is steady?

Just how steady can a camera be held? To answer this question, I used an enlarger alignment device which is essentially a laser mounted in a box about the size and weight of a 35mm camera. From 30 feet, trying my best, the laser spot would dance around within about a 1.5-inch circle on the wall. Using trigonometry, this corresponds to jittering within a solid angle of about 0.24˚. (You might try the same experiment with a laser pointer securely taped to a camera.)

The next question is how rapidly the laser spot moved within the circle. Without sophisticated instrumentation, I chose to use published medical data for the frequency of normal human nervous system tremor. The normal frequency range is 4-12 Hz. I assumed that my tremor rate was in the middle of that range, 8 Hz. In half a cycle, 1/16th second, a handheld camera may be expected to swing through 0.24˚, which translates to an average tremor of 0.24 x 16 =3.8 ˚/sec.

Film resolving power

How can we relate this jitter of 3.8 ˚/sec to the effect on image sharpness? Image sharpness is limited by the film’s resolving power, which for Tri-X is 100 lines per mm. If the image projected onto the film during exposure moves less than, say, half of a line spacing, we’ve probably achieved the maximum sharpness.

With resolving power of 100 lines per mm, half the line spacing is 0.005 mm. For a 35mm camera with a 50mm lens, the angle of view is about 45˚ and the dimension of the film is, duh, 35 mm. With a little math, jittering the camera 3.8 ˚/sec is seen to correspond to 3.1 mm/sec. To limit image movement during exposure to 0.005 mm, the exposure time should be 0.005 / 3.1 = 0.0016 sec. This would call for a shutter speed slightly faster than 1/500th second (compared to the rule-of-thumb speed of 1/50th sec).

Clearly, the conventional rule of thumb does not come close the achieving maximum image sharpness. It only works because the resultant blurring due to camera shake may not be noticeable for small enlargements.

Conclusion

I propose a revised rule of thumb: use at least twice the shutter speed called for under the old rule. For example, using a normal lens, use, say, 1/125th second rather than 1/60th second. Even better results can be achieved by using up to ten times the old rule’s shutter speed, i.e., 1/500th second in the example given.

[petiot]

thank you CyberDyneSystems ;), sorry Roger_Cavanagh


dan

[Jorge]

Interesting math example. If shutter speed was the only key to sharpness I would keep'em fast. However, when you are close to max aperture I think stopping down can often result in more sharpness than increasing shutterspeed.

[MarkH]

Should all photography be done using a tripod?

Or maybe each photographer needs to decide for themselves what level of perfection is good enough. Isn't this similar to calculation depth of focus? There is only one plane in focus, anything not on that plane is just not in focus?

[daveh]

Yes this is true of DOF too. I think it's good to keep reminding people about this though because a lot of people buy their first digicam and look at the shots on screen which is like looking at a 20"x30" print. Frequently they notice some lack of sharpness and blame the camera. It's good to remind people that a 20" x 30" image is a good test of the photographer as well as the camera.

[Pekka]

jorge wrote:
Interesting math example. If shutter speed was the only key to sharpness I would keep'em fast. However, when you are close to max aperture I think stopping down can often result in more sharpness than increasing shutterspeed.

As a side note: with good lens sharpness difference from open to f8 is not that big in the center of the lens. Well, with most great lenses open is not optimal but the next aperture up is already very good.

Here's one 50/1.4 crop of f/2 1/200 ISO200 test shot:

http://photography-on-the.net/10D/f2.jpg

[Yance]

It is a rule of thumb so there is some leeway for it and there are other variables to consider. Some people also have steadier hands than others. The bottom line is if the image is more critical and you have any concerns about sharpness - use a tripod!