Is the "1/mm" rule universal?

[xpatUSA]

. . or is it hangover from the glorious days of film, when "everybody" shot 35mm cameras with 100 ASA film and rules were needed because folks were perhaps less technical than today, what with the web and that?

I ask because I now have four cameras all with different pixel sizes. Suppose I shoot a far-off target with each camera having a non-IS 50mm lens. The rule says 1/Fmm = 1/50 sec or speedier gives a good chance of a blur-free shot, eh?

Now my pixel sizes range from 18.24um (binned low resolution) down to 4.33um. So, if my hand shakes by some amount, say the equivalent of 9um at the sensor, my feeling is the high-res camera would show some shakes but the low-res camera would not. (Trying to keep it simple here; mentions of Airy, Abbe, Rayleigh, Nyquist, et al are strongly discouraged).

Should there be an additional factor in "the rule" to account for this?

OTOH, is the rule itself dead? Does anybody actually use it?

[NorthernFocus]

IMO the rule is badly out of date. Personally I aim for 1/2x mm. And that is "equivalent" mm. So for example if I'm shooting a Nikon DX sensor camera w/300mm lens, I try to keep ss at 1/1000 or better when hand held.

[mikesan]

The rule worked fine for me 60 years ago. Now I use a tripod (and occasionally a cane).

[TonyW]

To me all rules are only guidelines - I am too much of an anarchist. In any case, the rule was never universally applicable. For example, with a fast moving target you always needed a faster shutter.

As lenses get better and pixels get smaller, you need a faster shutter speed to overcome camera shake to take advantage of the improvement. On the other hand, there are occasionally images where a slight lack of sharpness is not so important. I would normally aim for a faster shutter than the rule requires if conditions allow, perhaps by a factor of two, even with IS, but if I had to compromise I often would, depending the sort of picture. I have interesting pictures at 1/8s hand held.

Regarding the numbers you quote, it is an interesting question whether 9um is acceptable or not. It might depend on whether you have an anti-aliasing filter or not and whether you have a Bayer array or not. (I seem to remember that you have a Sigma camera without a Bayer array)

[AlwaysOnAuto]

Ever since learning of this 'rule' I've tried to remember to follow it, but I keep forgetting. My memory has become a steel sieve lately.

[Shadowman]

Probably specific to type of viewfinder used to compose/focus also. With a mirrorless or compact the camera is held away from the body, whereas with DSLR the camera is held close to the face. Plus, weight of cameras are very different with some being mostly plastic and others metal.

[AlwaysOnAuto]

uh, I use an EVF on my mirrorless so very rarely hold it away from my body, John.

[dje]

Trying to keep it simple here; mentions of Airy, Abbe, Rayleigh, Nyquist, et al are strongly discouraged

Ted I can't believe I'm reading this ....

I'm not an "old school" tog so I can't vouch for the origin of the rule but I suspect it did specifically relate to 35mm film. The size of the film or sensor is significant I think - for a given field of view with a given viewing size, 9um will be more significant on a crop sensor than a FF. Pixel size probably only comes into it when viewing at 100% because the smaller the pixels, the larger the magnification at 100% viewing.

The "rule" or some variation of it is probably in the category of "something to bear in mind" along with other factors when setting SS.

Dave

[Shadowman]

uh, I use an EVF on my mirrorless so very rarely hold it away from my body, John.

Alan,

Mine has an optional EVF attachment, I chose not to purchase.

[xpatUSA]

IMO the rule is badly out of date. Personally I aim for 1/2x mm. And that is "equivalent" mm. So for example if I'm shooting a Nikon DX sensor camera w/300mm lens, I try to keep ss at 1/1000 or better when hand held.

Thanks for reminding me of the 35mm equivalent part of the "rule", which muddies my example in the OP a bit. Two of the cams are 1.7 crop, one is 1.5 crop and one is 2.0 crop.

So, taking the 1.5 crop, you would go 50mm x 1.5 gives 75mm, then 1/2x75mm = 1/150 sec or thereabouts?

Now, s'pose those Nikon DX pixels are 5um pitch and you decide to go and buy a cam with 2.5um pitch - would your "rule" change to maybe 1/4x mm?

[Manfred M]

Frankly what people tend to forget about the "rule" is that it also assumed that the viewer was looking at an 8x10 print (about A4 size) at a distance of around "arms length". It also assumed the enlargement was made from a 35mm negative, so shooting medium format (which was what the pros were doing) would be even sharper.

So does the "rule" still apply, sort of, but there are a lot more variables involved. If you shooting for 8-1/2 x 11 (A4) prints using a full frame camera with a non-stabilized lens and are looking at printing the full frame (not cropped) image, yes, the rule is probably just as valid as it was in the film days. Start throwing in crop frame sensors, stabilized lenses and other variables, things get a bit more complex. I haven't done any comparison testing so any answers would be an educated guess.

If you plan to view on a computer screen, then things get even more complicated. Screen size, resampling and a whole host of other questions crop up.

[tao2]

It was never a "rule" but a rule of thumb, arrived at through experience and acquired knowledge. Like all rules of thumb, they are flexible enough tae be adapted or ignored on a shot by shot basis. One person's rock solid 1/250th. is another's palsy.

It's not the resolution or the pixels - it's the crop factor needing taken intae account. Shooting a 50mm@ 1/50th follows the rule but if yer shooting a 2x crop factor 50mm then ye have an angle of view of a 100mm lens so adjust tae 1/100th?

Things ah normally don't say - then wish ah hadn't...crop factor - when ah always (normally) say Focal Length Multiplier. Not only is it a much more elegant phrase, it's much more accurate as well.

[jcuknz]

The rule assumes that you know how to hand hold and how to release the trigger without unduly shaking the camera. I did a trial way back and found no difference between holding camera to my eye and viewing the image on the LCD at bent arms length. so I try to follow the guideline but am aware that it also depends on if the subject is moving and you are tracking with it. It is much harder to get good results of stationary subjects ... then too there is the amount and degree of post production you are capable of.
Then all this talk about crop sensors is mumble gumble IMO as it applies the the effective or equivalent focal length to that of the 35mm film camera or full frame digital. Some people simply do not seem to know the rule correctly ... never mind it is only a guideline to be followed or ignored as you personally work

So if you can hold a camera steady and know how to gently release the shutter and do not have a damm fool mirror flipping up out of the way to let you expose the sensor then the rule works fine. Then of course there is the weight of the camera to be considered ... why somebody using a speed graphic could shoot at 1/30 but likely a P&S is not a hope.

As Manfred alluded to .... the degree of enlargement also affects the situation as any film worker who examined their contacts for a great shot to be completely dis-appointed when they tried to make a 12x10 enlargement

[george013]

I'll take as an example a picture with motion blur. I do that for that's something that can be measured. The motion of the camera results in a motion of the image of x mm. I say mm.

First the comparison between the FF and the crop-camera. There is no difference between those concerning motion blur. A 100mm lens on a FF will give the same motion blur as on a crop camera. X mm will be x mm.

Secundly the comparison between difference focal length. A larger focal length means a smaller angle of view. Let's say your camera has a movement of 1 degree. A 50mm lens has an angle of view of 47 degree, a 500mm lens an angel of view of 5 degree. A motion of 1 degree is resulting in a motion blur going over 1/47 part of the sensor or 1/5 part of the sensor.

Thirdly the pixels.A D700 has a pixelsize of 0.0085mm, a D800 0.0049. So a motion blur on a D800 contains 1.8 time as much pixels as on a D700. To gain the same motion blur in pixels on a D800 as on a D700 your shutterspeed must be 1.8 times faster.

Fourthly the human factor. The former arguments are more arguments concerning the camera/lens but it is the humans factor that causes the motion mostly itself. It's obvious that there is a difference between a person with Parkinson or not. It will be allways a rule of thumb. Everybody has to find out his own boarders and even they can change.

Keep in mind that arguments above counts for 100% view, 1 sensor pixel = 1 monitor pixel. On a print it's different again, then it print resolution will be involved.

George

[Tringa]

While it depends on the person there is going to be a shutter speed at which virtually no one will be able to hold a camera sufficiently steady enough not induce camera shake.

Therefore a guide to when, on average, this could occur seems a reasonable starting point.

I too have heard it stated in terms of 1/(focal length of the lens x crop factor), but until I started digital photography I had never heard any rule/guideline.

When I first took up photography in the 1960s I remember it being said that the slowest hand held shutter speed for a normal lens (normal meaning 50 or 55mm) on a 35mm camera was 1/30th second and for longer lenses the shutter speed should be faster, but I don't recall any specific 'rule'.

Dave

[dem]

A larger focal length means a smaller angle of view. Let's say your camera has a movement of 1 degree. A 50mm lens has an angle of view of 47 degree, a 500mm lens an angel of view of 5 degree. A motion of 1 degree is resulting in a motion blur going over 1/47 part of the sensor or 1/5 part of the sensor.

Here we go. This is the rational behind the 1/(focal length of the lens x crop factor) rule of thumb, the ~1/x functional dependence of it. Nothing to do with pixel size, AA filter or colour filter array pattern.

So it is the Field of View that gives the x^-1 dependence, and the coefficient in front of x^-1 depends on the print size and on how much you trust your image stabilisation. With a 5-stop IS, one can shoot handheld at 1/10 s, 300 mm ff eq and still get a sharp image.

[Mike Buckley]

Does anybody actually use it?

I always use it. I learned that with my camera and capture technique, I'm safest when shooting at 1/((1.5 x focal length)x1.5) for focal lengths at about 50mm and below. Otherwise, I shoot at 1/((1.5 a focal length)x2). The multiplier value of 1.5 takes into account the crop factor of my camera. None of my lenses have image stabilization.

[Simon Garrett]

I use it as a guide. That is: where possible I keep to a slowest shutter speed of 1 / (focal length times crop factor).

With VR/IS, clearly you can go slower, but in my experience of Nikon VR, it's not 100% reliable. In other words: if the lens says it gives 3 stops VR improvement, it seems to be "3 stops improvement most of the time, sometimes little or no improvement".

It's not directly related to pixel size, but rather to print/image size and viewing distance. However, if you're taking advantage of high resolution (smaller pixels) to get larger prints, then clearly it does relate to pixel size indirectly.

[george013]

I use it as a guide. That is: where possible I keep to a slowest shutter speed of 1 / (focal length times crop factor).

With VR/IS, clearly you can go slower, but in my experience of Nikon VR, it's not 100% reliable. In other words: if the lens says it gives 3 stops VR improvement, it seems to be "3 stops improvement most of the time, sometimes little or no improvement".

It's not directly related to pixel size, but rather to print/image size and viewing distance. However, if you're taking advantage of high resolution (smaller pixels) to get larger prints, then clearly it does relate to pixel size indirectly.

Viewing digital images for sharpness is done at 100%. And then it's really pixel related. It's something else if you say that you don't see it on a print x by y cm.
When the D800 was introduced there was a technical guide, http://www.nikonusa.com/en_US/o/Y6wr...alGuide_En.pdf
I referenced to this guide before as being an example how important pixelsize is.

George

[Simon Garrett]

Viewing digital images for sharpness is done at 100%. And then it's really pixel related. It's something else if you say that you don't see it on a print x by y cm.

Viewing images at 100% gives you an view of the maximum sharpness (without additional sharpening).

However IMHO it does not always give a realistic assessment of whether an image sharpness is fit for purpose. If it were so, one would discard many usable images. Rather, one needs to assess whether an image is sharp enough for the required purpose: whether it's for print or for display on a monitor, the size of the image, the viewing distance and so on.

It's misleading to say the least to suggest that a 36 Mpixel D800 requires a tripod in circumstances where a 12 Mpixel D700 would not (for example). If the circumstances require a 10x8 print and the D700 produces a sharp hand-held image, then so will the D800 at the same shutter speed.

However, the 36 Mpixel camera will allow a (linear) enlargement 1.7 times larger than a 12 Mpixel image before resolution becomes an issue. If one is going to enlarge an image to the maximum size the 36 Mpixel allows, then the lower camera-shake-limited shutter speed is reduced by the same factor of 1.7.

When the D800 was introduced there was a technical guide, http://www.nikonusa.com/en_US/o/Y6wr...alGuide_En.pdf
I referenced to this guide before as being an example how important pixelsize is.

George

The section in that guide on motion blur and use of a tripod is IMHO very misleading. It is true to say that you need a tripod for a 36 MPixel D800 when you wouldn't for a lower resolution camera if and only if you intend to enlarge the image more than you would have done with a lower resolution camera.