Holger Merlitz
Well-known member
Thank you, Jonathan, your 'A' is noted. Glad to know that you like my reviews!
Cheers,
Holger
Cheers,
Holger
-
Welcome to BirdForum, the internet's largest birding community with thousands of members from all over the world. The forums are dedicated to wild birds, birding, binoculars and equipment and all that goes with it.
Please register for an account to take part in the discussions in the forum, post your pictures in the gallery and more.
Measurement of human visual distortion (1 Viewer)
- Thread starter Holger Merlitz
- Start date
Holger Merlitz
Well-known member
Dear All,
I have now summarized the results in an update of the same web-page:
http://www.holgermerlitz.de/globe/test_distortion.html
Altogether, 56 test persons have participated, thanks again for your efforts!
As some of you had already speculated, the data appear fuzzy and their interpretation is tricky. This experiment is not easily carried out, and there are some pitfalls and potential sources of errors. As a consequence, it is not possible to pinpoint any particular distortion value that would be typical for the majority of test persons. This could mean that either such a value does not exist, i.e. there exists a wide range of distortion values among the population, or the experiment is too inaccurate, or both of them.
Anyway, some results appear to be sure: Helmholtz's suggestion (k=0.5 being a typical value for the human visual distortion) can be ruled out, the measured distortion was lower with almost every test person. It is also obvious that there are quite a few people with a visual distortion larger than k=0.8 (corresponding to k-values of smaller than 0.8), and those would surely observe a globe effect with distortion-less binoculars. Hence, the manufacturers should make sure to have some pincushion distortion added to the optical formula, with k=0.7 being a reasonable compromise. The times of the angle condition (k=0) seem to have passed, never again we will have to suffer such a high amount of pincushion distortion. Let's hope that the manufacturers refrain from shifting to the other extreme of complete absence of distortion.
All the best,
Holger Merlitz
I have now summarized the results in an update of the same web-page:
http://www.holgermerlitz.de/globe/test_distortion.html
Altogether, 56 test persons have participated, thanks again for your efforts!
As some of you had already speculated, the data appear fuzzy and their interpretation is tricky. This experiment is not easily carried out, and there are some pitfalls and potential sources of errors. As a consequence, it is not possible to pinpoint any particular distortion value that would be typical for the majority of test persons. This could mean that either such a value does not exist, i.e. there exists a wide range of distortion values among the population, or the experiment is too inaccurate, or both of them.
Anyway, some results appear to be sure: Helmholtz's suggestion (k=0.5 being a typical value for the human visual distortion) can be ruled out, the measured distortion was lower with almost every test person. It is also obvious that there are quite a few people with a visual distortion larger than k=0.8 (corresponding to k-values of smaller than 0.8), and those would surely observe a globe effect with distortion-less binoculars. Hence, the manufacturers should make sure to have some pincushion distortion added to the optical formula, with k=0.7 being a reasonable compromise. The times of the angle condition (k=0) seem to have passed, never again we will have to suffer such a high amount of pincushion distortion. Let's hope that the manufacturers refrain from shifting to the other extreme of complete absence of distortion.
All the best,
Holger Merlitz
Last edited:
Surveyor
The more I understand, the more I understand why I
Thanks for the update Holger. I have followed your work and find it fascinating.
I do wish you had had a far greater number of respondents to get a better handle on the margin of error, although, just following the respondents on BF, the SD was better than I expected from such a small sample and the average was close to your overall sampling.
In particular, I like your admonition, “Additionally, the distortion curves should be smooth, avoiding any local extrema or inflection points.” About 18 months ago I mentioned a pair of binoculars that I used that were nauseating to use in motion and posted a picture of the grid. The edges had reverse curves in them and they are not pleasant if viewed near those edges. I believe I remember Henry Link commenting that he had run into that situation before also.
http://www.birdforum.net/showpost.php?p=1534374&postcount=26
Please let us know of any updates.
I do wish you had had a far greater number of respondents to get a better handle on the margin of error, although, just following the respondents on BF, the SD was better than I expected from such a small sample and the average was close to your overall sampling.
In particular, I like your admonition, “Additionally, the distortion curves should be smooth, avoiding any local extrema or inflection points.” About 18 months ago I mentioned a pair of binoculars that I used that were nauseating to use in motion and posted a picture of the grid. The edges had reverse curves in them and they are not pleasant if viewed near those edges. I believe I remember Henry Link commenting that he had run into that situation before also.
http://www.birdforum.net/showpost.php?p=1534374&postcount=26
Please let us know of any updates.
henry link
Well-known member
The photos of distortion in the Swarovski 8.5x42 SV from the thread below show the same compound distortion, in a milder form, as Ron's Leupold 7x20. Both appear to match the type of distortion in the BPO 7x30 discussed by Holger. I've noticed this same kind of wave shaped linear distortion in a few other binoculars and telescope eyepieces.
http://birdforum.net/showthread.php?t=175077
http://birdforum.net/showthread.php?t=175077
Last edited:
Holger Merlitz
Well-known member
Dear Henry,
Your observation is correct: The anomalous distortion curve of the 8.5x42 is of quite peculiar shape, somewhat similar to the BPO's. This is one reason why much more people complain about the globe effect of the 8.5x than of the 10x Swarovision. This odd distortion curve adds to the impression of an image rolling 'over the edge' in the outer parts of the field. Through computer animations, these effects are now well understood and I am confident that in future designs our experience will be taken into account.
All the best,
Holger
Your observation is correct: The anomalous distortion curve of the 8.5x42 is of quite peculiar shape, somewhat similar to the BPO's. This is one reason why much more people complain about the globe effect of the 8.5x than of the 10x Swarovision. This odd distortion curve adds to the impression of an image rolling 'over the edge' in the outer parts of the field. Through computer animations, these effects are now well understood and I am confident that in future designs our experience will be taken into account.
All the best,
Holger
