Hi,
I was wondering what the closest distance a 17mm lens can shoot clearly when the focusing is set to infininty?
I was wondering what the closest distance a 17mm lens can shoot clearly when the focusing is set to infininty?
superdave said:Hi,
I was wondering what the closest distance a 17mm lens can shoot clearly when the focusing is set to infininty?
blurblock said:What camera? 35mm SLR, 35mm DSLR, Medium Format camera? What aperture?
superdave said:I'm using a Canon 10D. Does the aperture setting and camera type (film or digital) affect the focusing distance? I tot it should be the same....
blurblock said:Yes it will .... so what aperture setting? The camera type affects the focusing distance due to difference in the circle of confusion.
superdave said:ok... I'm probably looking at a 2.8...
To better give an idea of what I plan to do... below is a sample picture of a shot I took while wakeboarding. I'm being dragged behind a little dinghy about 5 feet from the rider and my camera is being enclosed in a wet case which after its sealed, I am unable to make any adjustments to the camera settings. The shot was taken with a cheapo russian fisheye, so results are not great and it doesn;t work well with my flash.
I was thinking of getting another wide angle lens, something like a 17mm f2.8 for this kind of shots. Because the action is so fast and the framing difficult, I'd prefer to set the lens to infinity so the subject is in focus, regardless of how far they are from me... which is subject of course, to my question of what the min focusing distance is when the lens is set to infinity....
I was able to get the subject in focus (set to infinity) from just 5 feet away on the fisheye.
student said:I don't know about the 17 mm.
On my Canon 1V, using my 14 mm at f4, focus will be ok from about 4-5 feet away.
blurblock said:I don't think you can get the subject to be in focus at infinity from just 5 feet away at f/2.8, you mean that person is only 1.5 meters away from you? If you want to set to infinity from just 5 feet at 17mm you need to be at f/8.
For f/2.8, you are required to have a distance of about 2.7 meters or 9 ft away to get infinity. That is cutting it very thin as this is the distance of the near limit of acceptable sharpness where the focus point is not the subject.
I don't think there is anything wrong with your lens and your flash. Look at all those back light, chances are the flash is fooled by the background lighting to produce very little power to lighten up the subject. I suggest you switch to manual for your fill in flash instead.
knoxknocks said:you thinking of using a 17-35 f/2.8?
if I'm not wrong, what blurblock is talking about is calculating the hyperfocal distance and then dividing that by 2 to get the near limit of acceptable sharpness. When you focus at the hyperfocal distance, anything from 1/2 of the hyperfocal distance to infinity is in focus. Unfortunately, the 17-35 doesn't have a DOF scale, so you'll have to compute.
blurblock said:Whatever gives you the idea near limit of acceptable sharpness is Hyperfocal distance divided by 2?
Hyperfocal Distance = (Focal Length of the Lens x Focal Length of the Lens) / (Aperture x Circle of Confusion)
Near Focus limit = (Hyperfocal Distance x Distance of Subject in Focus) / (Hyperfocal + (Distance of Subject in Focus - Focal Length of the Lens))
Thus when you want to know thread starter wanted to know what is the minimum distance for infinite, I need to know the Aperture, Camera Type and Focal Length.
enzochang said:If far focus is infinity ... Hyperfocus is 10 feet ... nearest limit is 5 feet ...
If you have a DOF scale lens ... take a look .. its always half ..
blurblock said:Whatever gives you the idea near limit of acceptable sharpness is Hyperfocal distance divided by 2?
Hyperfocal Distance = ((Focal Length of the Lens x Focal Length of the Lens) / (Aperture x Circle of Confusion)) + Focal Length of the Lens
Near Focus limit = (Hyperfocal Distance x Distance of Subject in Focus) / (Hyperfocal + (Distance of Subject in Focus - Focal Length of the Lens))
Thus when you want to know thread starter wanted to know what is the minimum distance for infinite, I need to know the Aperture, Camera Type and Focal Length.
knoxknocks said:wah...i gong liao :bsmilie:. when focus at hyperfocal distance, DOF extends from 1/2 * hyperfocal to infinity no? sorry if i cause confusion.