Minimum Shutter Speeds - DSLR advantage?

[photophorous]

I've read this rule of thumb several times: To avoid blur from camera shake when shooting hand held, a good minimum shutter speed is 1 over the focal length. So, for a 30mm lens, you might be able to get away with 1/30 second shutter speed...assuming you're careful.

Does that mean you are capable of shooting at slower shutter speeds with a DSLR vs. 35mm, at an equal angle of view, because of the 1.5X crop factor? Using the 1/focal length "rule", there's a 2/3 stop difference for the same angle of view.

Can anyone comment on my logic here? Does this make sense, or am I missing something?

In all the reading I did before I bought my DSLR, I never heard anyone mention this...what seems to be an advantage of smaller sensors.

Thanks,
Paul

[another view]

Interesting - never thought about that, but it sounds logical. And yes, lay off the coffee for best results! With some practice, you can break that rule by a stop or more, so that 30mm lens could be at 1/15 or possibly even slower.

In real life, I don't really think about it too much - if I'm shooting a 50mm lens then I'm shooting a 50mm lens and try to keep it at 1/60 if possible. But I see what you're saying - that 50mm lens is closer to a 75 or 80 in angle of view so there is an advantage there. I think a bigger advantage of DSLR's is their ability to switch ISO speeds whenever you want and very clean high ISO shots compared to 35mm.

[walterick]

I'll agree with Steve that the obvious first advantage is selectable (or automatic) iso. But as for the handholding rule...

Is the rule based upon lens focal length or magnification of subjects? Does a 50mm lens on a DSLR magnify its subjects more, thereby requiring a higher shutter speed than on an SLR? Good question!

I've got a feeling Michael Fanelli is going to pop in here with the correct answer to this one

[Spec A!]

I completely see the logic in the question, and it made me think about this:

Is there any less light coming in the lens? Is there really a 2/3rd stop difference?
Is the physical size of the lens any different?
Because the FOV is more narrow, is this the reason why you'd have shake?

[dmm96452]

My answer would be no. Whatever your limitations are with a film SLR should remain with a D-SLR. The reason is that a 30mm lens is a 30mm lens is a 30mm lens. So whatever camera movement there is with a 30mm lens on a film camera or full frame D-SLR will be there on a APS-C sized sensor as well. The only difference is that with a standard lens on an APS-C camera some of the image circle is lost. Any movement that would cause blurring is the same.

[Asylum Steve]

...my guess is it wouldn't make any difference.

The smaller camera sensor (crop factor) simply means you are getting less of a recorded image. The image itself is not smaller than a full-frame sensor, just cropped.

So, it seems to me the relationship of the lens focal length to the size of the recorded image would be the same, full-frame sensor or not. And therefore the "blur factor" would be the same, meaning the shutter speed rule would be the same...

[mjs1973]

My way of thinking is that the opposite is true and that you are at a dissadvantage with a DSLR and a long lens. They way I have always thought of it is that the narrower your field of veiw, the harder it is to hand hold the shot (wide lens=slower shutter speed, long lend=faster shutter speed). Lets say that you have a 500mm lens on a DSLR with a 1.5x crop factor. You have a field of veiw = to 750mm. Following the "rule" you would now need a shutter speed of 1/750 of a second to hand hold the shot instead of 1/500 on a film SLR. Then again, I have been wrong before.

[another view]

Does a 50mm lens on a DSLR magnify its subjects more

Nope - like Asylum Steve says, you're just getting a smaller crop at the same magnification. Because of that angle of view difference, a 50mm is usually compared to a 75mm.

Is there any less light coming in the lens?

No, this doesn't change. Maybe you're thinking of it being kind of like using a 1.4x teleconverter where you would use a stop? In the case of a TC, the focal length is longer by a factor of whatever the TC is designed for (1.4x, 2x, etc). Any lens without a TC mounted on any camera is always the same focal length - again, it's just the angle of view that changes.

For example, the exaggerated perspective that you get with a 20mm lens is the same on a 1.5x DSLR even though you only get the angle of view of a 30mm lens. In real life, most of that exaggeration that you wind up with (looks great if done right) is near the outside of the frame usually and since the crop factor cuts this out, it doesn't have the same feel to it. I don't think that there's anything technically different about it, but the shots with it don't look that way. A fisheye has most of it's distortion at the edge, so the 16mm fisheye that you used with a 35mm SLR doesn't do what it used to either. Of course, all of this goes away with a full-frame DSLR...

[walterick]

I think Asylum Steve has it here. The 50mm lens is magnifying the subject the same amount on both cameras. But a DSLR is essentially enlarging the image - which would also enlarge any blur! So maybe Michael is correct in saying that DSLR's are at a disadvantage ;)

[photophorous]

Thanks for all the replies, everyone. I gotta admit though...I'm still not sure I understand.

I guess I'm leaning towards Michael's point of view. I think what it comes down to is the amount of magnification (lens) + enlargement (sensor/print). This rule of thumb works with 35mm film, because we are assuming a limit to the enlargement of the final print...usually about 11x14. But, if film grain technology where to shrink the grains down to a quarter of the TMAX size, and you enlarged a 35mm photo up to 16 x 24, I bet that rule of thumb wouldn't be good enough. You'd need a faster shutter speed, because at that degree of enlargement a tiny amount of blur would be visible. Same goes for digital. So, it's really a combination of the magnification given by the lens, and the enlargement of the final print (or file), the later of which is affected by the 1.5x crop factor as well as the camera's true resolution. So, with a 16 MP, full frame, DSLR, the rule of thumb probably works just fine if you are printing under at sizes that are common for 35mm film. But, I bet if you print bigger, it doesn't. So, that's why I think Michael is right. But, I'm not feeling real confident about that.

Anyone agree or disagree?

Paul

[another view]

Probably safest to go with that - take the 30mm lens and use 1/45 sec as your minimum handheld speed. This rule isn't really a rule though - just a good starting point. Like I said, with practice you can probably get below 1/30 pretty easily.

[readingr]

Probably safest to go with that - take the 30mm lens and use 1/45 sec as your minimum handheld speed. This rule isn't really a rule though - just a good starting point. Like I said, with practice you can probably get below 1/30 pretty easily.

Arrgh me harties (sailors voice)

This is easy to figure out - its a compination of magnification and weight of item doing the magnification.

Example take a pair of bins with 30x magnification and another set with 30x magnification but heavier - now figure out which you can hold most steady. Its normally the lighter of the two. ask any sailor.

Now I have the Canon AE1 and the Canon Powershot Pro 1 both with 28mm lens. I have difficulty holding the AE1 steady at 1/6 sec but the Pro its a breeze. I probably wouldn't try it with the AE1 far to heavy.

See picture on my WEB site taken with the Pro
http://www.readingr.com/mygallery/La...272%20640.html

Roger

[photophorous]

Arrgh me harties (sailors voice)

This is easy to figure out - its a compination of magnification and weight of item doing the magnification.

Example take a pair of bins with 30x magnification and another set with 30x magnification but heavier - now figure out which you can hold most steady. Its normally the lighter of the two. ask any sailor.

Now I have the Canon AE1 and the Canon Powershot Pro 1 both with 28mm lens. I have difficulty holding the AE1 steady at 1/6 sec but the Pro its a breeze. I probably wouldn't try it with the AE1 far to heavy.

See picture on my WEB site taken with the Pro
http://www.readingr.com/mygallery/La...272%20640.html

Roger

Are you sure that the Powershot has a 28mm lens...not just a 28mm "equivelant" lens? I don't know, but I assume it's not a full frame sensor, so 28mm would not be very wide.

I disagree with your weight logic. Assuming you can hold both with out straining, a heavier camera would shake less, not more. The law of inertia says objects at rest tend to stay at rest. If it's heavier (more mass) a greater force has to be applied to move it. Now, if it's so heavy you're having trouble holding it, that can be a problem, but I doubt that's the case with an AE1.

So, I'm thinking this may just prove my original assumption. If the lens on your Powershot is actually much shorter then 28mm (as would be required to get a wide angle on a small sensor), a 1/6 second exposure could make a blur free image possible. Hmmm....

Paul

[readingr]

Are you sure that the Powershot has a 28mm lens...not just a 28mm "equivelant" lens? I don't know, but I assume it's not a full frame sensor, so 28mm would not be very wide.

I disagree with your weight logic. Assuming you can hold both with out straining, a heavier camera would shake less, not more. The law of inertia says objects at rest tend to stay at rest. If it's heavier (more mass) a greater force has to be applied to move it. Now, if it's so heavy you're having trouble holding it, that can be a problem, but I doubt that's the case with an AE1.

So, I'm thinking this may just prove my original assumption. If the lens on your Powershot is actually much shorter then 28mm (as would be required to get a wide angle on a small sensor), a 1/6 second exposure could make a blur free image possible. Hmmm....

Paul

Correct its a 7.2mm which is 28mm equivalent

However, you have to remember the strain your adding to the muscle to hold said weight, which causes the muscle to start trembling sooner the heavier things get. We sailors who spend some time at dusk looking for unlit buoys prefer the lighter bins as you can hold them steady for longer.

So the time available for a steady shot reduces with the weight of the object being supported. Add age, caffine, alcohol, into the equation and this changes everything.

Roger

[photophorous]

Correct its a 7.2mm which is 28mm equivalent

However, you have to remember the strain your adding to the muscle to hold said weight, which causes the muscle to start trembling sooner the heavier things get. We sailors who spend some time at dusk looking for unlit buoys prefer the lighter bins as you can hold them steady for longer.

So the time available for a steady shot reduces with the weight of the object being supported. Add age, caffine, alcohol, into the equation and this changes everything.

Roger

Ah ha! With a 7.2mm lens you were able to take a reasonably sharp photo at 1/6 second. That's pretty close to the rule of thumb. Advantage: digital!

I see what you're saying about the weight. Long term use of a heavy camera could have a negative effect on your ability to cope with the caffeine and alcohol in your blood. But, for a one time situation, I still think heavier is better...up to a reasonable limit (couple of beers/lattes).

Please excuse my ignorance, but what are these "bins" you're refering to?

Paul

[another view]

bins = binoculars

I can't hold my 80-200 f2.8 at 80mm anywhere near the shutter speed I can hold my 85 prime at. That zoom is much longer and heavier, and I've heard about that rule that you should always use the longest focal length of a zoom (200mm in this case) regardless of the focal length that you're actually using. I know I can hold it at less than 1/200 though!

[photophorous]

bins = binoculars

I can't hold my 80-200 f2.8 at 80mm anywhere near the shutter speed I can hold my 85 prime at. That zoom is much longer and heavier, and I've heard about that rule that you should always use the longest focal length of a zoom (200mm in this case) regardless of the focal length that you're actually using. I know I can hold it at less than 1/200 though!

That's why I love this site. I learn something everytime I'm here.

That makes sense about your 80-200, and goes to show my inexperience. I've never had a big lens like that. It probably exceeds the comfort level for my heavier-is-better arguement.

Paul

[Spec A!]

No, this doesn't change. Maybe you're thinking of it being kind of like using a 1.4x teleconverter where you would use a stop?

Yeah I understand that- my questions were posed to point out that there's certain factors other than just focal length that come into play. The most important thing in shake being the exposure- the amount of light coming through the lens wouldn't change between a 35mm and a DSLR. The shutter speeds will be the deciding factor, and what you can confidently hand hold is what really matters.

You guys seem to have answered it pretty well. I am still curious though about the FOV. The APS sensor'd DSLR will crop out part of the image, not necessarily magnify it correct? And this is because the image circle's projection hits the film plane earlier in it's path (if you will) than it does on a 35mm? The That's one thing I'm not 100% read-up on.

[Franglais]

The APS sensor'd DSLR will crop out part of the image, not necessarily magnify it correct? And this is because the image circle's projection hits the film plane earlier in it's path (if you will) than it does on a 35mm? The That's one thing I'm not 100% read-up on.

The APS sensor is in exactly the same place as the 35mm film, sitting in the midle of the image circle. It's just smaller in size so it only records the center part of the image.

I have just one thing to add to this debate - the 1/focal length rule was fine for 35mm film but now 10Mpix+ DSLR's are looking more like medium format. If I was doing an image where I wanted all the detail then I would either use a tripod or else up the minimum shutter speed.

Charles

[walterick]

Guys, my understanding of the 1/focal length rule was not because of the weight of the lens but the degree of magnification. Just take a 28mm lens, balance it on something (to take the weight out of the equation) and watch how little your scene "jumps" with your tiny hand movements. Now hook your 200mm lens with a 1.4 tc and your 1.6 digital crop and balance it on the same support - watch how the tiniest movement makes your subject jump around the frame. It was my understanding that the magnification was the gremlin here, not the weight. Steve's example of the 85mm prime vs. the 80-200 zoom is a great example. Or even more dramatic - the prime vs the Sigma 50-500. Incorporating the 1/focal length rule here is going to provide a different result in each example. An 85mm prime weighs nothing compared to the 80-200 or 50-500. If the 1/focal length rule is designed to compensate for the weight of a lens I don't see it doing a very good job in this example! The equation fails to take the variety of lens weights into account and deals only with the magnification.

That's my understanding at least I'm sure somebody will refute me on it ;)

[another view]

The equation fails to take the variety of lens weights into account and deals only with the magnification.

That's my understanding at least I'm sure somebody will refute me on it ;)

Not me, that's absolutely correct IMO. The "rule" has nothing to do with the size or weight of lens or camera, or one person's ability to hold a camera more solidly than another's. Like I said, with practice you can get better at this. It's really only a guideline and should be used as a starting point. Don't pass on taking a shot just because you can't quite hit the 1/FL number.

[SmartWombat]

I don't think a DSLR is necessarily at a disadvantage.
Particularly if the sensor is full frame it's identical to film

Seriously though I agree with Michael.
The crop factor of a amaller sensor gives the same angle of view in the frame as the longer lens on full frame.