Please remind me

[forrest64]

What is the multiplying factor of the shutter speed when for using telephoto lenses?

It's something like if your at 1/125 with a 50mm then use X with a 200mm.

Please remind me.

Thanks......

[PacAce]

Are you talking about the rule of thumb for the slowest shutter speed for safely handholding a camera? I'm sure you're going to be many differing opinions on this but if that's what you are asking, to answer your question, multiply the lens focal length by the camera crop factor, then take the reciprocal of that as your shutter speed (or the closest speed available on the camera). For example, for a 200mm lens, if you are using a 20D which has a crop factor of 1.6, 200 X 1.6 = 320. The reciprocal of 320 is 1/320. So set your shutter speed to the one closest to that, erring on the slower side and that would be 1/250.

[forrest64]

Yep that's it. I have a 10D so the crop factor is the same. Thanks.

[forrest64]

By the way I'd rather err on the faster side of 1/320 to assure sharp pictures (ISO and light conditions allowing.)

[PacAce]

By the way I'd rather err on the faster side of 1/320 to assure sharp pictures (ISO and light conditions allowing.)
Doh! You're absolutely right! That's what I should have said. Sorry. :confused:

[forrest64]

Used your calculation to estimate shutter speed using a telephoto lens (using the next highest speed) and the pictures were sharp on closeup subjects (unlike the day before.)

Thanks...

[forrest64]

I'm beginning to think some of what people call "back focus" when using telephoto lenses might in reality be too low of shutter speeds. I thought this too when I took some pictures of ducks in which 8 out of ten were "out of focus." Using the calculated minimum shutter speed the problem seems to have dissipeared. Of course this solution needs plenty of light or high ISO's. Then again I could use fill flash.

[robertwgross]

Using the calculated minimum shutter speed the problem seems to have dissipeared.

If you get a chance, try using a long telephoto lens with Image Stabilization turned on.

---Bob Gross---

[forrest64]

I'd love to. I don't currently own one. I guess I could rent one but I'm afraid what the results would do to my budget.

[dhbailey]

One thing to keep in mind with IS is that if your subject is moving, the IS makes clear pictures more difficult to get, since it never really locks on. The newer generation of IS have two different axes of IS, both of which are switchable, so you can keep the vertical IS on while leaving the horizontal IS off and that helps a lot, from what I recall having read. I only have the 75-300 USM IS and while the IS has helped me get some good shots in lower light (read that as slower shutter speeds) I find that I am not all that thrilled with the lens.

[PhotosGuy]

You can adjust that rule depending on whether the subject is moving parallel to you (use the rule), or directly toward/away from you (slower shutter speed).

Leo: :D:D I wondered about that! ;)

[forrest64]

You can adjust that rule depending on whether the subject is moving parallel to you (use the rule), or directly toward/away from you (slower shutter speed).

Leo: :D:D I wondered about that! ;)

I was more concerned about camera movement with a long lens attached. I was getting blurry pictures even though the subject, ducks, were not in motion.

[Curtis N]

Here's what Norm Carr posted on another forum when discussing a similar topic. Just some food for thought.

"How much wine you drank last night. How much coffee you drank this morning. How windy it is. Whether you're standing up straight, or not. How far you walked (or ran) to get to where you are. How flat the ground is you're standing on. The weight of your camera. Whether you're hot, or cold. How long you've been holding up your camera already. How fit you are. How old you are. Whether you camera has a mirror. Whether you have something solid to lean against. What you consider to be acceptable sharpness for the reproduction and subject of your picture.
Just a few of the things I can think of that might affect your ability to steadily hand-hold a slower shutter speed. I bet a physiologist could think of many more. However you think about it, the notion of applying a ridiculously simplistic formula to hand-held shutter speeds is an exercise in futility.

I wonder where this myth ever came from."

[forrest64]

With all due regard to Norm Carr the formula may be simplistic but it isn't ridiculous. Certainly every one would agree that faster shutter speeds make for sharper pictures. The formula is a useful guide for determining a minimum shutter speed to take pictures of static subjects while holding the camera by hand. Obviously other variables such as hurricanes and standing on trampolines can skew the results. All I know is that it worked for me for the particular photographic situation I was involved in and I thank PacAce for sharing it with me.


Mark...

[Curtis N]

...the formula may be simplistic but it isn't ridiculous.
I agree, Mark.

Nothing wrong with thumbrules, as long as we realize they're just guidelines and that there are many factors in play. I try to keep the shutter speed faster than the focal length when I can, knowing that everything is a trade-off.

I've been doing some shooting lately in a theatre. Not much light, so I'm getting shutter speeds of 1/60 or 1/30 with a 75-300 zoom lens (wide open at 1600 ISO). Am I afraid to take the shots, knowing that some of them will be blurry? Heck no. I fire away, and I get a fair percentage of "keepers." Doesn't cost me a dime to trash the shots that turn out to be crap.

Ain't digital photography great?

[KennyG]

I did a lot of shots over the weekend at 1/250 with the 300 and 1.4 TC (420mm). They are perfectly sharp but I must throw them away because I have broken the rules. By my sarcasm you may gather I have no respect for this particular rule. The simple answer is, experiment until you find the right shutter speed for the circumstances that produces the effect you want. Trust me, there is no 'shutter police' checking up on you and you won't be woken at 3am by a knock on the door because you took a picture at 1/60 and 300mm.

[Curtis N]

there is no 'shutter police' checking up on you and you won't be woken at 3am by a knock on the door because you took a picture at 1/60 and 300mm.
You mean I don't have to hide all my EXIF data under my mattress anymore? What a relief!

[ed2day]

One thing to keep in mind with IS is that if your subject is moving, the IS makes clear pictures more difficult to get, since it never really locks on.

I don't understand this. IS works off motion-sensing gyros and not anything in the image. Or so I thought. Am I missing something?

[Wazza]

If you're producing 300mm and 1/60th, I would be putting a big sign on my door. ;)

I'm always breaking that rule also, and haven't had one run in with the police yet.