.Experiment no. 2
. Not having close-up lenses handy, I used a made in China, el-cheapo reading glasses of +2.00 dioptres costing a few pounds. The lenses are not that great, I think plastic and on reflections they do not seem to have very good surface accuracy.
With the Minolta 8×23 compact AF 8 autofocus binocular, I placed one half of the spectacles in front of the right objective of the binocular. I was surprised how close I got.
With the binocular focused at 2 m, and using the spectacle lens, the computer screen letters were sharp at about 0.4 m.
With the binocular focused at the far point the computer screen to objective distance was about 0.5 m. These are rough figures.
The autofocus worked at these close distances, as I suspected it would.
The distance from the centre of the autofocus window to the edge of the objective is about 2 cm or less than 1 inch. If one was viewing insects I don't know whether or how this displacement would be relevant.
There is also the point that the dioptre correction range of this binocular is from -12 to +4, which is 16 dioptres.
Again, I don't know how one can use this to give a very large focus range.
. But the autofocus seems to work at close distances although it was taking about 0.3 seconds to get the focus point rather than 0.1 seconds approximately when used normally.
The image of the letters on the computer screen was not good, but I was only holding the spectacle glass in front of the objective, and it was certainly not positioned or angled correctly. In addition the contrast was not that good, but I think that is because the spectacle lens to binocular gap was completely open where it should be in a blackened tube.
If done properly, with an optically good +2 dioptre close-up lens, I think the results would be reasonable.
As mentioned, this binocular was also available as a 10×23, although I haven't come across one yet.
. Not having close-up lenses handy, I used a made in China, el-cheapo reading glasses of +2.00 dioptres costing a few pounds. The lenses are not that great, I think plastic and on reflections they do not seem to have very good surface accuracy.
With the Minolta 8×23 compact AF 8 autofocus binocular, I placed one half of the spectacles in front of the right objective of the binocular. I was surprised how close I got.
With the binocular focused at 2 m, and using the spectacle lens, the computer screen letters were sharp at about 0.4 m.
With the binocular focused at the far point the computer screen to objective distance was about 0.5 m. These are rough figures.
The autofocus worked at these close distances, as I suspected it would.
The distance from the centre of the autofocus window to the edge of the objective is about 2 cm or less than 1 inch. If one was viewing insects I don't know whether or how this displacement would be relevant.
There is also the point that the dioptre correction range of this binocular is from -12 to +4, which is 16 dioptres.
Again, I don't know how one can use this to give a very large focus range.
. But the autofocus seems to work at close distances although it was taking about 0.3 seconds to get the focus point rather than 0.1 seconds approximately when used normally.
The image of the letters on the computer screen was not good, but I was only holding the spectacle glass in front of the objective, and it was certainly not positioned or angled correctly. In addition the contrast was not that good, but I think that is because the spectacle lens to binocular gap was completely open where it should be in a blackened tube.
If done properly, with an optically good +2 dioptre close-up lens, I think the results would be reasonable.
As mentioned, this binocular was also available as a 10×23, although I haven't come across one yet.
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