Minimum shutter speed hand-held

[kencaleno]

You may recall my stating that I recommend 3 times focal length of lens as minimum shutter speed for hand-held shots-And many here argued, quoting shutter speed=reciprocal of focal length, was right-(Although there is no trace of the origin of this formula) Well I was going through my photography library at home,the other day,and here it is-straight from the Master-Ansel Adams-a quote from his book, "The Camera." (Published by Little,Brown & Company 1980) page 116:

" A test I conducted some years ago,photographing leafless trees against a sky, indicated that, using a normal, (50mm) lens on a hand-held camera-The slowest shutter speed that ensured maximum sharpness was 1/250th sec." So he recommended 5 times lens focal length as minimum shutter speed for maximum sharpness hand held.

Are you going to argue that Ansel Adams got it wrong? regards, Ken

[Raigoki]

wow! thanks for the info!
have researched some about shutter speed for hand-held...

Min. Shutter Speed

just wondering though if Oly's in-body IS would reveal the same result with lower shutter speed...

[wulf]

Would I argue that Ansel Adams got it wrong? Possibly. I'd like to see what he could do with my 50mm set up (50mm f/1.8 E series lens and Nikon D40 body) first. Being small and light, I imagine he could probably do better than 1/250s for optimal sharpness. I would also be interested to know the sensitivity of his film - even at ISO 200 (lowest setting on the D40) I can often pull off shots at 1/50s or slower (although that does mean the error rate starts to increase - I appreciate that I have the luxury of firing off multiple shots and not having to change film plates).

Wulf

[kencaleno]

Originally Posted by wulf

Would I argue that Ansel Adams got it wrong? Possibly. I'd like to see what he could do with my 50mm set up (50mm f/1.8 E series lens and Nikon D40 body) first. Being small and light, I imagine he could probably do better than 1/250s for optimal sharpness. I would also be interested to know the sensitivity of his film - even at ISO 200 (lowest setting on the D40) I can often pull off shots at 1/50s or slower (although that does mean the error rate starts to increase - I appreciate that I have the luxury of firing off multiple shots and not having to change film plates).

Wulf

What have film plates got to do with it? You cannot use a 10x8 camera hand-held!
Ansel used leicas, (smaller,lighter,than your D40-and 50mm f2 Summicron,just about the sharpest lens on the planet)and nikons as well as view cameras-and as he states 1/250th sec for MAXIMUM sharpness-in other words, to equal using a tripod.Ask any pro,and he/she will tell you the same-you may not tell the difference on a 6x4 print, but you will on a 30"x 40" print.

[kencaleno]

Here's a controlled test to prove things:

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 Kodak 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 film's 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, jiggling the camera 3.8˚/sec is seen to correspond to 3.1 mm/sec (so a 1-sec exposure would be hopelessly blurred–which even a beginning photographer well knows). To limit image movement during exposure to 0.005 mm, one-half the film's resolving power, 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" 50mm 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.

Question: What About a Digital Camera?



Now, the size of the film affects the angle of view for a given focal length. For example, we know that a “normal” lens (one that has about a 45º angle of view, roughly the same as human vision) for a 35mm camera is a 50mm lens. For my medium format camera, with a film dimension of 60mm, the "normal" lens is about 85mm (50mm x 35/60 = 85.7mm), and the minimum shutter speed per the “old” rule is 1/85 second, say 1/125; make it one or two stops faster for my rule, and it’s 1/250 or 1/500 second.

Implicit in all of this is that the “resolving power” (lines per mm) of film is the same no matter what camera it’s in or the size of the film. The minimum shutter speed is proportional to the film size and the film’s resolving power, and is inversely proportional to the field of view of the lens (degrees). The lens' focal length is “in there” somewhere, because the field of view (degrees), lens focal length, and the film size are all interrelated.


Resolving Power of Digital Cameras

Roy reports that for his particular digital camera a 14mm focal length is “normal.” Since we know that a 50mm lens is “normal” for a 35mm camera, the size of the array of pixel sensors (the equivalent “film size”) within his digital camera must be about 35mm x (14/50) = 9.8 ≈ 10mm (less than a third the size of 35mm film). (For simplicity, I’m using the width of the image, the long dimension; it would be more accurate to use the diagonal dimension of a 35mm frame.) This gives us one of our “unknowns,” and we now must estimate the resolving power (lines/mm) of Roy’s digital camera.

Roy didn’t specify his camera’s number of pixels, but let’s say that it has 4.0 megapixels. Then the spacing of the pixels is about: √[(10mm x 10mm) / (4.0 x 106 pixels)] = 0.005mm. I’m ignoring two fine points: 1) the sensor array is likely rectangular, not square, and 2) the spacing between parallel rows of pixel sensors will be larger, by a factor of √2, in a diagonal direction across the array.

With this pixel spacing of 0.005mm, we couldn't expect to resolve lines with the same spacing. Probably, we could expect to begin resolving lines with twice that spacing, 0.01mm (i.e., two pixels for each line). The equivalent resolution is: 1/0.01 = 100 lines/mm (coincidentally, the same resolving power as Tri-X film).

To adapt the old inverse-of-focal-length rule to this digital camera at “normal” focal length, we need to multiply the “old rule” of 1/14 second by the ratios of image resolution. Thus, the “old rule” minimum shutter speed for the digital camera with a “normal” lens = (1/14 sec) x (100 lines/100 lines) = 1/14 sec ≈ 1/15 second.

Roy’s “old rule” answer of 1/14 second is correct, but serendipitously so. That speed is only correct for my assumption of a 4 megapixel camera. If it were 2 megapixel or 8 megapixel, with the same 10 mm sensor array size, his answer would have been off by a factor of √2 ≈ 1.4.

Interpreting Digital Camera Specs

Out of curiosity, I checked the specs for my Kodak DX6440 digital camera, a 4-megapixel “point and shoot” model with a zoom lens. Here is selected information published in the user’s manual

•Image Sensor: 1/1.25 inch charge coupled device (CCD), 4:3 aspect ratio

•Lens focal length: variable, 33–132

•Slowest shutter speed, @ wide lens, Auto Mode: 1/60 sec

•Normal lens focal length: not given

CCD image sensor arrays are sized in an arcane manner, a legacy from early television days (for more details, refer to the website referenced below). But suffice it to say, the long dimension of a 1/1.25 inch array is about 5.6mm. We may now compute the “normal” lens focal length, by factoring the known “normal” lens size of 50mm for a 35mm camera: 50mm x 5.6/35 = 8mm. But wait, this “normal” focal length doesn’t even fall within the zoom lens’ supposed range, 33–132mm. What gives?

Engraved on the lens itself is this data: “33mm–132mm (Equiv).” The manufacturer has listed the focal length range using the “equivalent” focal lengths for a 35mm camera. Therefore, the equivalent “normal” focal length of 50mm corresponds to a true focal length of 8mm, and the lens’ real range of focal lengths varies from 5.3mm to 21mm.

The spacing of the pixel sensors in this CCD chip is about: √[(5.6mm x 5.6mm)/(4 x 106 pixels)] = 0.0028mm. As explained above, we might expect to resolve lines with twice that spacing: 0.0028mm x 2 = 0.0056mm. This corresponds to a resolving power of 1/0.0056 = 179 lines/mm (nearly double Tri-X film’s resolving power, 100 lines/mm).

We may now compute the minimum shutter speed to achieve maximum image sharpness. At the “normal” focal length of 8mm, the minimum shutter speed, using the “old” rule is: (1/8 sec) x (100 lines/179 lines) = 0.070 sec ≈ 1/15 sec. Per my revised rule of thumb, increase this speed by one or two stops, so select 1/30–1/60 second as the minimum shutter speed. Indeed, the Kodak specifications for this camera, when in the Auto Mode, calls for a minimum shutter speed of 1/60 second at wide angle. With my “new” rule of thumb for selecting minimum shutter speed, I have seemingly rediscovered what Ansel Adams and even Kodak have known all along.

What Ansel Adams Said "Tests I conducted some years ago, photographing leafless trees against the sky, indicated that, using a normal lens with a hand-held camera, the slowest shutter speed that ensured maximum sharpness was 1/250 second. I found that even with firm body support image sharpness was noticeably degraded at 1/125 second, a speed that many photographers consider safe for hand-holding a camera with normal lens."



Since Roy was intrigued by my citation of Ansel Adams’ findings, I went back to Ansel’s book, The Camera, page 116, which states:

I’m quite sure, based on the context of Ansel’s statement, that he conducted his experiment with a 35mm camera, and that his recommended minimum shutter speed of 1/250 applies to a 35mm camera with a 50mm (normal) lens. What is the equivalent speed of for a medium format with film dimension of, say, 60mm, also equipped with a normal lens? It is: (1/250 sec) x (35mm/60mm) = 0.00233 ≈ 1/500 sec, or twice as fast as for the 35mm camera.

In general, the equivalent shutter speeds between two different camera/film systems is inversely proportional to the ratio of the lens’ focal lengths. Therefore, if 1/25 second is the desired shutter speed for Camera A with a 30mm lens, the equivalent shutter speed for Camera B, also with a 30mm lens, is 1/25 second—irrespective of the relative film sizes of the two cameras. This is true in general, assuming the films have the same resolving power.

Similarly, if two film cameras, A and B, taking different film sizes, each have lenses with the same angle of vision, but of course with different focal lengths (F), the equivalent shutter speed (S) is given by: SA = SB x (FA/FB).

My studies merely corroborate those of Ansel, but Ansel’s conclusions regarding shutter speed seemingly never achieved widespread notice; adherence to the “old” reciprocal-of-focal-length rule continues to this day. Perhaps with the Internet available to disseminate these findings, the “new” rule will gain greater acceptance.


® Doug Criner, 2004

Regards,Ken

[wulf]

What sensitivity rating would his film have been? That would make a significant difference. What other caveats are there? The fact I'm only using a 6MP camera with shots coming out about 3000x2000px is going to quash my hope of razor sharp results - I would be printing at a maximum of about 67dpi to produce an image at 30" x 40" and so would lose the benefits of any potential gain in sharpness because of the camera body (even if my lens would come anywhere near to his Summicron).

Therefore, I'm not suggesting AA got it wrong given the conditions of his experiment but I am suggesting that this is working with a much finer degree of precision than is necessary for most photographers to deal with. If someone can get good results at 1/focal length or slower, then those results speak for themselves.

Wulf

[OsmosisStudios]

Originally Posted by kencaleno

" A test I conducted some years ago..."

I wont argue he was wrong, but wasnt using either A) an SLR or B) proper technique. Remember, Ansel Adams was quite some time ago and things have changed. He also says that it's a test he conducted: its in no way scientific for many reasons.

I know where I can handhold a shot: I'll just stick to that.

kthxbai.

[vandergus]

Who knew Ansel Adams was so jittery. Maybe this was later in life when he was getting old and shaky.

Seriously though. There's no point in trying to set up some super rigorous test to try to prove what the right formula is because the user has too much influence on the results. Any scientist will tell you that for a test to be valid it must be independent of the person performing the test. Camera shake is a phenomenon introduced by the user so it would be very hard (read impossible) to create a test to determine the minimum shutter speed that is independent of the user.

1/focal length is a RULE OF THUMB. It's not like calculating the field of view or the proper exposure. The only way to know what shutter speed you can shoot at and get sharp pictures is to try it yourself. Go get your camera, take several pictures at several different shutter speeds and see which one's are sharp. It'll take five minutes. Not that complicated.

Ken, If you want to shoot at 1/3*focal length, great. But don't tell everyone else that they have to.

[shiraq]

is all about your power to keep the camera still. I make sharp photos on 1/60 for example with different kind of lense.

[kirbinster]

Remember that his lens and cameras did not have vibration reduction technology.