[BikeGeek]

I've got an inexpensive digital camera that I've been taking on rides with me. When it's on the auto focus setting the rider is usually through the frame before the camera focuses and shoots. I've been playing around with setting the focus distance. The camera has several settings, ie. 0.5 m, 1 m, 3 m, etc. The final setting is infinity (∞). What is that exactly?

 

[Toshi]

you'd use infinity when focusing on the horizon, for instance. effectively it will keep objects from that point in to about 100m or so in acceptable focus (very rough figure! depends on your sensor's size, resolution, lens you're using, print size; google for "hyperfocal distance" if you're interested).

 

[BikeGeek]

Thanks!

 

[binary visions]

Find something in the path that the rider will be crossing through, and half press the shutter button and hold it there. The camera will focus, and when the rider actually enters the viewfinder, press it all the way.

The camera should take the picture immediately, and the rider will be in focus. Even inexpensive digital cameras are usually fast enough to capture riding shots if you pre-focus.

...and when you get a few good ones, make sure to post 'em

 

[MikeD]

you'd use infinity when focusing on the horizon, for instance. effectively it will keep objects from that point in to about 100m or so in acceptable focus (very rough figure! depends on your sensor's size, resolution, lens you're using, print size; google for "hyperfocal distance" if you're interested).

For digital cameras with tiny focal-length lenses, infinity focus is going to come a long way before 100m...

It might be in your owner's manual; actually, if it's not, there's a serious problem with that manual. Just look up the manual focus option and it should give you the exact distance at which infinity focus occurs (ie, once you've focused at this specific distance, everything beyond that point will also be in focus.)

MD

 

[BikeGeek]

For digital cameras with tiny focal-length lenses, infinity focus is going to come a long way before 100m...

It might be in your owner's manual; actually, if it's not, there's a serious problem with that manual.

The manual blows.

 

[TN]

I always use BV's method when shooting with my el-cheapo HP digi-cam. Yours may not have a fast shutter (like my HP) so you might have to pan with the action to keep it from turning out blurry.

 

[Toshi]

For digital cameras with tiny focal-length lenses, infinity focus is going to come a long way before 100m...

good point. for a nikon 5700 at 7.1 mm (i made up this figure, but it's full wide on compact canons so shouldn't be too far off) and f/2.8, hyperfocal distance will be 2.23 m according to this calculator: http://www.nikonians.org/html/resources/guides/dof/hyperfocal2.html

dang small sensors . for a camera more like mine (i used nikon d1h, 28mm, f/4) the hyperfocal distance would be at 9.83 m. i guess my 100 m figure was way off, altho it is true for longer focal lengths on dSLRs ink: (my 135 f/2 has a hyperfocal length on this theoretical d1h of 455.8 m at f/2, 114 m at f/8)

 

[Toshi]

I always use BV's method when shooting with my el-cheapo HP digi-cam. Yours may not have a fast shutter (like my HP) so you might have to pan with the action to keep it from turning out blurry.

every camera has a shutter fast enough to freeze mtb action, assuming that figure is around 1/500. you just need to make the camera open the aperture and/or raise the sensitivity (iso) enough so that it can achieve 1/500 with a proper exposure.

 

[BikeGeek]

Good tips! I'll try that pre-focus thing if it ever stops raining.

 

[MikeD]

I've found the manual-focus method to be the best with compact digis. Just use a setting with some good depth-of-field, either with high ISO settings or wide apertures, and add some pan to reduce blur and help separate the rider from the background.

 

[jacksonpt]

Find something in the path that the rider will be crossing through, and half press the shutter button and hold it there. The camera will focus, and when the rider actually enters the viewfinder, press it all the way.

The camera should take the picture immediately, and the rider will be in focus. Even inexpensive digital cameras are usually fast enough to capture riding shots if you pre-focus.

I've tried this a few times and never had good luck. I'm sure it's something I'm doing (or not doing), but...

It might be in your owner's manual; actually, if it's not, there's a serious problem with that manual. Just look up the manual focus option and it should give you the exact distance at which infinity focus occurs (ie, once you've focused at this specific distance, everything beyond that point will also be in focus.)

Would this be a good alternative to using a very narrow aperture setting (f/16) for greater focal depth? I have a hard time getting enough light into the camera with narrow aperture settings and faster shutter speeds.

 

[binary visions]

I've tried this a few times and never had good luck. I'm sure it's something I'm doing (or not doing), but...

What's "bad luck"? Poorly focused shots? Rider not being in the frame the way you want them to be?

 

[jacksonpt]

Blurry pics - rider, background, foreground, everything. Initially I thought I was moving the camera while the pic was being taken, but I don't think that's the problem every single time.

 

[binary visions]

Blurry pics - rider, background, foreground, everything. Initially I thought I was moving the camera while the pic was being taken, but I don't think that's the problem every single time.

It sounds like the camera isn't locking the focus properly.. or you're not focusing on the right area. Try taking a couple without any distractions like waiting for the rider - half press the button, shift what you're pointing at, and snap the shot. See if the area you focused on originally comes out sharp.

Maybe your camera just doesn't support that? I'm not sure I've ever seen a camera that didn't! The camera might have a constant focus feature that overrides your "locked" focus area. Some digital cameras do this (constant focus) when you put them in "sports mode" - I never use the specialized modes on my camera.

 

[Toshi]

Would this be a good alternative to using a very narrow aperture setting (f/16) for greater focal depth? I have a hard time getting enough light into the camera with narrow aperture settings and faster shutter speeds.

noooo. like you said the shutter speeds will drop. also depth of field is effectively unlimited at sane (as in not really close up) subject distances on point 'n shoot digitals, as MikeD correctly pointed out. finally, diffraction becomes an issue for small cameras at small apertures. a slr might suffer from diffraction starting at f/16, but small cams see the effect sooner, and that's why most won't even let you select an aperture smaller than f/8.

 

[MikeD]

Would this be a good alternative to using a very narrow aperture setting (f/16) for greater focal depth? I have a hard time getting enough light into the camera with narrow aperture settings and faster shutter speeds.

It depends on how far away your subject needs to be for infinity focus...and if you're using a camera with a sub-15mm focal length lens, pretty much everything will be in focus at nearly any aperture setting.

You shouldn't need to stop all the way down to F/16 on a compact digi at any time, really, to get some depth of field.

MD

 

[binary visions]

You shouldn't need to stop all the way down to F/16 on a compact digi at any time, really, to get some depth of field.

I don't even know of a compact digi on the market that will allow an aperture that small... 98% of them stop at f/8 as Toshi pointed out. Many stop at larger than that (f/6 or f/5).

 

[jacksonpt]

It sounds like the camera isn't locking the focus properly.. or you're not focusing on the right area. Try taking a couple without any distractions like waiting for the rider - half press the button, shift what you're pointing at, and snap the shot. See if the area you focused on originally comes out sharp.

Maybe your camera just doesn't support that? I'm not sure I've ever seen a camera that didn't! The camera might have a constant focus feature that overrides your "locked" focus area. Some digital cameras do this (constant focus) when you put them in "sports mode" - I never use the specialized modes on my camera.

My camera does it... it's a Sony DSC-S85. About 4years old, but still a decent camera. What I've done in the past is prefocused on the part of the trail where the rider is going to be when I want the picture taken (i.e. on a particular obsticle). Then, once the rider gets to that section of trail, I press the shutter button the rest of the way.

 

[jacksonpt]

noooo. like you said the shutter speeds will drop. also depth of field is effectively unlimited at sane (as in not really close up) subject distances on point 'n shoot digitals, as MikeD correctly pointed out. finally, diffraction becomes an issue for small cameras at small apertures. a slr might suffer from diffraction starting at f/16, but small cams see the effect sooner, and that's why most won't even let you select an aperture smaller than f/8.

OK... I guess then it would be the closest thing my camera has to a manual focus mode. Setting the focal distance still has a similar effect as setting the aperture. And by the way, I don't use F/16 (I don't think my camera goes that small). I generally use F/6.