Manual Focusing Question

[JimbobJimbo]

Ok, this may be a newbie dSLR owner question, but I was wondering. If you have a lens that does not have a distance scale how do you manualy focus to infinity? I have a Canon XSi, and using a 18-55mm f3.5-5.6 and 55-250mm f 4-5.6 kit lenses with no distance scale. Thanks

 

[Geoff_M]

Most dSLRs have what's called an "electronic rangefinder" (Nikon's term, anyway). Basically it's an "in focus" indicator that will illuminate when the image is in focus when focusing manually. The distance range scales on lenses have never been practical for the sake of focusing, even before the days of auto-focusing cameras. Their only real practical use is to provide an estimation of the depth-of-field range for the selected f-stop. "Infinity" also isn't really a focusing point.

 

[thomas998]

you look through the viewfinder and slowly turn the focus ring... when what you want to be in focus is in focus - you're done.

 

[dr_zero]

To infinity wouldn't you turn it all the way in one direction? Like on mine its all the way to the right.

 

[Geoff_M]

To infinity wouldn't you turn it all the way in one direction? Like on mine its all the way to the right.

It sounds nonsensical, but most lenses will go "past" infinity. This is to allow for variabilities in the manufacturing process. If you'll notice, even when you focus on something like a far away mountain, you will still be able to turn the lens' focus ring a little further.

 

[dr_zero]

It sounds nonsensical, but most lenses will go "past" infinity. This is to allow for variabilities in the manufacturing process. If you'll notice, even when you focus on something like a far away mountain, you will still be able to turn the lens' focus ring a little further.

Ah! makes sense guess I will have to look closer at that.

 

[GrillMouster]

I think you mean to ask about hyperfocal distance. For maximum depth of field use the smallest aperture (highest f-stop) and focus on a point one-third of the way into the scene (hyperfocal distance). Small apertures allow less light through, so use a slow shutter speed and a tripod. You can increase the ISO, allowing you to use a slightly faster shutter speed (possibly allowing you to hand-hold), but I highly recommend using the lowest ISO possible and a tripod or some other method of stabilizing the camera. You may also want to use a remote shutter release or the timer, and mirror-up (if your camera allows it).

When you do the above, much of the scene may still appear to be out of focus in the viewfinder, but that's because the lens aperture is always wide open at it's maximum size, and doesn't stop down until the shutter is released. So, what you see through the viewfinder is what the image would look like if you were to set the lens at its maximum aperture (lowest number f-stop). When using a different aperture setting, you could use the depth of field preview button (if your camera has one) or take the image, review it in the LCD, adjust your settings, then shoot again.

 

[boBQuincy]

A convenient way to focus at infinity is to use the auto focus to focus on something very far, then switch the lens to manual without disturbing the focus.

 

[Pea-n-Me]

Good explanations of How to.

Now, who wants to tackle why you'd Want to?

Will include this thread on The Learning Curve for future reference since it does come up here and there.

Thanks

 

[MICKEY88]

Good explanations of How to.

Now, who wants to tackle why you'd Want to?

Will include this thread on The Learning Curve for future reference since it does come up here and there.

Thanks

fireworks would be a good reason to want to, you're not going to be able to focus on them as they go off, so you pre-focus, switch to manual, and leave the focus where it is, for fireworks shots..

 

[JimbobJimbo]

fireworks would be a good reason to want to, you're not going to be able to focus on them as they go off, so you pre-focus, switch to manual, and leave the focus where it is, for fireworks shots..

That was the main reason that I asked the question. Everywhere I've read says for fireworks to focus to infinity by using the distance scale, but my lens doesn't have a distance scale. Thanks for all the replies

 

[BuzzLiteyear]

Good explanations of How to.

Now, who wants to tackle why you'd Want to?

Will include this thread on The Learning Curve for future reference since it does come up here and there.

Thanks

fireworks would be a good reason to want to, you're not going to be able to focus on them as they go off, so you pre-focus, switch to manual, and leave the focus where it is, for fireworks shots..

Lightning would be another example. Auto focus does not work well/at all for distant thunderstorms.