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Photography Q&A
Focussing on infinity in the dark with continuous autofocus lens rings
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<blockquote data-quote="okulo" data-source="post: 499529" data-attributes="member: 40687"><p>Ever since I got my first SLR, a Pentax ME Super, I have had a fascination with taking long exposure shots in near darkness. With my D70's lenses, there was still a distance scale on the lenses which allowed easy approximated focussing and the lens focussing stopped at infinity. However, since I bought my D5500, I have encountered difficulty focussing in the dark and I first discovered this during the recent lunar eclipse when the eclipse was total, the Moon was virtually invisible to the naked eye and the camera could not focus on it. Turning the focus ring all the way wasn't an option because the lens I have, the 18-300mm f3.5-6.3 has Buzz Lightyear focussing; i.e.beyond infinity and turning to the lens's soft stop is well past infinity.</p><p></p><p>I have been seeking a solution to this problem and most answers seem to suggest either using a torch to illuminate a nearer subject or focussing on a distant object such as the Moon, which is OK if it is visible; neither is very helpful for focussing on a distant scene when there is not enough light and no Moon.</p><p></p><p>I think I may have come up with a workaround. In daylight, I focussed on a cloud and then, using a reference point on the lens, such as the ridges or white lines by the Auto/Manual switch or VR On/Off switch, select the nearest ridge on the focus ring's rubber and then turned the ring past infinity until it reached its soft stop and then counted the ridges on the focus ring back to the reference point, on my lens this was eight. I then unfocussed and turned the focus ring to the beyond infinity soft stop and, using a reference point, turned it back eight focus ring ridges and the lens was focussed perfectly on the cloud.</p><p></p><p>I had read that the reasoning behind these lenses focussing beyond infinity and have continuous focus rings is to reduce wear on the end stop when the autofocus is searching but also due to inconsistencies caused by changes in temperature on certain elements in the lens. I'm not going to say that I know for a fact that either of these reasons are true but I have tried using the eight ridge rule I have measured and it seems to work consistently and given that I always close the aperture to allow longer exposures, any slight inaccuracy will be buffered in depth of field.</p><p></p><p>It is an inelegant procedure but quite simple once the initial measurement has been worked out. If anybody else has been looking for a solution to this problem, I hope this works for you too.</p></blockquote><p></p>
[QUOTE="okulo, post: 499529, member: 40687"] Ever since I got my first SLR, a Pentax ME Super, I have had a fascination with taking long exposure shots in near darkness. With my D70's lenses, there was still a distance scale on the lenses which allowed easy approximated focussing and the lens focussing stopped at infinity. However, since I bought my D5500, I have encountered difficulty focussing in the dark and I first discovered this during the recent lunar eclipse when the eclipse was total, the Moon was virtually invisible to the naked eye and the camera could not focus on it. Turning the focus ring all the way wasn't an option because the lens I have, the 18-300mm f3.5-6.3 has Buzz Lightyear focussing; i.e.beyond infinity and turning to the lens's soft stop is well past infinity. I have been seeking a solution to this problem and most answers seem to suggest either using a torch to illuminate a nearer subject or focussing on a distant object such as the Moon, which is OK if it is visible; neither is very helpful for focussing on a distant scene when there is not enough light and no Moon. I think I may have come up with a workaround. In daylight, I focussed on a cloud and then, using a reference point on the lens, such as the ridges or white lines by the Auto/Manual switch or VR On/Off switch, select the nearest ridge on the focus ring's rubber and then turned the ring past infinity until it reached its soft stop and then counted the ridges on the focus ring back to the reference point, on my lens this was eight. I then unfocussed and turned the focus ring to the beyond infinity soft stop and, using a reference point, turned it back eight focus ring ridges and the lens was focussed perfectly on the cloud. I had read that the reasoning behind these lenses focussing beyond infinity and have continuous focus rings is to reduce wear on the end stop when the autofocus is searching but also due to inconsistencies caused by changes in temperature on certain elements in the lens. I'm not going to say that I know for a fact that either of these reasons are true but I have tried using the eight ridge rule I have measured and it seems to work consistently and given that I always close the aperture to allow longer exposures, any slight inaccuracy will be buffered in depth of field. It is an inelegant procedure but quite simple once the initial measurement has been worked out. If anybody else has been looking for a solution to this problem, I hope this works for you too. [/QUOTE]
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Focussing on infinity in the dark with continuous autofocus lens rings
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