1/Focal Length Rule of Thumb

[joe_bailey2]

I have read that 1/FL should be used for minimum shutter speed to

prevent camera shake blur. If I attach a 2x converter to my 200mm

lens, should my minimum shutter speed be at least 1/400 - or 1/500

(rounded to nearest speed). Also, how much should my IS help. I've

read about 3 stops, but does this mean I could go all the way down

to 1/60. Thanks.

[oceanphysics]

Well, if you put a teleconverter on it, it's a 400mm lens. So yes, assuming you take the rule seriously.

 

1/400 plus 3 stops is about 1/150.

[mcgarity]

Personally I have found that even shots taken with image stabilization benefit from faster shutter speeds. But if thats not possible do everything you can to help IS out and stabilize yourself and the camera. By bracing against a very solid object you can get sharp handheld shots at 1/20 of a second with an image stabilized 400mm lens. But even with IS you can get fuzzy ones at 1/400 of a second by just waving the camera around.

[danield]

1/400 plus 3 stops is 1/60 - roughly, but 1/125 (2 stops) may be safer.

[steve_dunn2]

<p>A 200mm lens with 2x teleconverter is a 400mm lens in every way. If this weren't so, manufacturers wouldn't make 400mm lenses; they'd make 200mm lenses with built-in teleconverters :-) So yes, you need to account for the TC when figuring out the minimum safe shutter speed for handholding.</p>

 

<p>Do keep in mind that this is a <em>guideline</em>, not a hard-and-fast rule, and that it's for <em>acceptable</em> sharpness in a moderate-sized print. Take the same shot at a substantially higher shutter speed, or using a decent tripod, and you <em>will</em> get sharper results. Will the extra sharpness be important? For a 4x6" print, probably not; for a 16x24" print, yes. If you've just run up a hill to get a better vantage point on some wildlife on the other side of the road (been there, done that, didn't have IS, didn't get a good shot) or have been drinking too much coffee, you can expect to need a higher shutter speed.</p>

 

<p>IS depends on the lens in question. The latest generation of IS is claimed to give a 3-stop benefit, so 1/60s should be OK on a 400mm lens. Older generations are only claimed to give a 2-stop benefit for telephoto shots, so you'd need 1/100s. The two IS lenses I've been using for the last few years (28-135 and 300/4) both have older 2-stop IS versions, and while I haven't really done formal testing of this, I believe that 2 stops is pretty safe, and occasionally I get more. I just bought a 70-200 IS, which has the latest 3-stop version, but haven't had a chance to see for myself if it really is that much more effective.</p>

 

<p>Also, is this full-frame or a digital body with a crop factor? I'm not certain that there's universal agreement on this, but personally, I believe that on a digital body with a crop factor, you have to take into account the crop factor when calculating a minimum safe shutter speed for handholding, because to make the same print size from the smaller "frame", you need to enlarge more, which magnifies any shaking. So if you put that 200mm lens and 2x TC on a 1.6-crop DSLR, instead of needing 1/400 as you do on a film body, I believe you need 1/640.</p>

[joe_bailey2]

Thanks for all the info. I actually just purchased a 1.4x for my 70-200 2.8L IS. I used the 2x example for the sake of even numbers. This will be going on my 5D, so there will not be any cropping factor.

[yakim_peled1]

<p> Not all IS lenses are created equal....</p>

<p> <a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00EsnE&tag=">http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00EsnE&tag=</a> <b></b> </p>

 

<p>Happy shooting, <br>

Yakim.</p>

[oceanphysics]

<i>1/400 plus 3 stops is 1/60 - roughly, but 1/125 (2 stops) may be safer.</i><p>

Yes, you're right. Not sure what math I was using there.