Shutter Speed - the "math" 1/(FL x 1.6)

Can someone please explain this to me ? I read that the proper SS that I should be using (M mode) should be AT LEAST 1/(FL x 1.6) -- since I have a crop camera.

Examples, I'm shooting a FL of 100mm ...

So for the best chance of a Sharp picture, my SS should be 1/(100X1.6) = 1/160 -- Is this correct? or do I have to take the "mm" into consideration ? And this is a MINIMUM SS, right?

another example - FL of 50mm - I would shoot at a minimum of 1/80 SS ... right?

Thanks in advance.

In theory, you've got it right on all counts. In reality, it will vary from person to person. Some with good technique and very steady hands may be able to get away with a slower shutter speed; some are less steady and may need a considerably higher one. Also (if we're talking about stationary subjects), using IS may allow you to shoot considerably slower without camera shake showing up.

In addition to what Veemac said, you need to consider enlargement size. The bigger the enlargement the faster the shutter speed.

e-k

Cody21 wrote in post #10196243
Can someone please explain this to me ? I read that the proper SS that I should be using (M mode) should be AT LEAST 1/(FL x 1.6) -- since I have a crop camera.

That is the rule-of-thumb which has been used for 35mm film cameras for decades, modified for the smaller APS-C format.

The one thing you need to realize is that this applies to ALL exposure modes, not just "M" (Manual) mode.

As said in the posts above, the rule-of-thumb will apply to various individuals (and different degrees of enlargement to present images) differently depending on how steadily they are able to hold a camera.

Another thing to keep in mind is that this applies only when the camera is being hand held. If it's on a tri-pod, rested on something, or you very stable like elbows on a wall, then this does not apply. A fast shutter speed does nothing magical to sharpen up pics. It just reduces the effect of camera motion.

Thanks guys -- makes sense.

What's the difference between, say, a 40d, and a 5dmark 2 when it comes to this?

Since pixel density is nearly the same on both cameras, wouldn't you need to use focal length x 1.6 on the 5d2 as well to get pixel level sharpness?

mikekelley wrote in post #10197422
What's the difference between, say, a 40d, and a 5dmark 2 when it comes to this?

Since pixel density is nearly the same on both cameras, wouldn't you need to use focal length x 1.6 on the 5d2 as well to get pixel level sharpness?

This question was recently beaten to death (as you already know): https://photography-on-the.net/forum/showthre​ad.php?t=860274 and E-K already answered it in this thread.

The rule of thumb is correct 1/(focal length x crop factor) but as suggested, it differs from person to person.

If I use good technique, I can quite often manage double the rule (up until it gets to about 1/2 sec). Shooting without care, I follow the rule pretty well. I find the breath holding gives the biggest effect (think snipers)

mikekelley wrote in post #10197422
What's the difference between, say, a 40d, and a 5dmark 2 when it comes to this?

Since pixel density is nearly the same on both cameras, wouldn't you need to use focal length x 1.6 on the 5d2 as well to get pixel level sharpness?

The quick synopsis (because I'm not gonna beat that dead horse any longer) is that a 40D's image needs to be magnified 1.6X as much as a 5D's to get the same size print or screen. Any shake will be magnified 1.6X in the process.

-js

With the new 70-200 the IS works wonders...

number six wrote in post #10197764
The quick synopsis (because I'm not gonna beat that dead horse any longer) is that a 40D's image needs to be magnified 1.6X as much as a 5D's to get the same size print or screen. Any shake will be magnified 1.6X in the process.

-js

So then it doesn't really matter, and we should strive for as high a shutter speed as possible on all cameras, making the 1.6x shutter speed rule a load of you know what?

I would suggest that is correct unless, your going so fast that you must increase ISO to unacceptable levels to compensate.

mikekelley wrote in post #10198307
So then it doesn't really matter, and we should strive for as high a shutter speed as possible on all cameras, making the 1.6x shutter speed rule a load of you know what?

Well, this "rule" is for minimum handheld shutter speeds. Personally, I don't think it's fast enough as a minimum and I try for 2X if I can. Not because I'm particularly shaky, but because we tend to print much larger than we used to in the 35mm film days, where that "rule" originated.

I have a 20 X 30 inch print over my desk, taken handheld with my 6.3 MP 300D. I would never have tried to print a 35mm film shot that large - in fact I think the largest print I ever did with film was 11 X 14.

I wouldn't say "as high a shutter speed as possible", though - there are tradeoffs. How about "high enough", which for me is usually safely 3X. No point in sacrificing noise performance or depth of field to arbitrarily get the shutter speed high.

-js

mikekelley wrote in post #10198307
So then it doesn't really matter, and we should strive for as high a shutter speed as possible on all cameras, making the 1.6x shutter speed rule a load of you know what?

Perhaps you've misread some posts? 1.6x is a guideline for the minimum shutter speed when shooting hand held.