Intro to aspheric lenses (to help you choose the best one)

Nominate your favourite 'informative' posts to place here, and links links to suppliers too.
Locked
Humpers
Posts: 82
Joined: 25 Aug 2012, 08:08
Location: Surrey

Re: Intro to aspheric lenses (to help you choose the best on

Post by Humpers » 26 Jan 2013, 16:01

some bloke wrote:This is incredibly in depth stuff - thanks Humpers.

The ahorton lens seems to have now switched from the best to the worst performer, I have never tried the kaidomain ones but it now looks like I should if I am reading your last results correctly? EDIT: Were I to feel I need more light which I don't right now but hey - guys like to play with torches lol..

I seem to have got something muddled because I think I read that thicker lenses are better than thinner ones. I'm slighly dyslexic and sometimes have trouble absorbing the written word when it's too long or deep so I've probably got that wong. :oops:
Just to remind everyone that I have issued a health warning about my results, so they do need to be verified in the field really before you ought to totally trust them.

The ahorton, with a particularly short focal length, does capture more of the output of, for example, the Oslon Black than any other lens. This is why in V1 and V2 of my table it came top. But at that point I hadn't realised quite how important the "point source effect" was, i.e. the LED appearing small to the lens at it's focal length. V3 of the table takes this into account, which is why the other lenses with a longer focal length have overtaken it.

To be honest I don't think there will be much difference in the field between the ahorton and the Kaidomain lenses as there's only a relatively small difference between 10,000 odd and 14,000 odd on my table. From my experiments I think the ahorton is also optically a much better lens than the Kaidomain and Ant Supplies lenses, so will let through a greater proportion of the light that's hitting it than the latter, but this is only my opinion so don't take it as gospel.

Regarding your point about thicker lenses being better than thin ones, it depends how you define "better". I think they generally are of better quality optically as they are harder to make than thin ones so only the better manufacturers produce the thicker lenses, and they tend to take more care over the materials they use, etc. But because there are a number of factors involved in making a good LED + lens combination for our purposes, thickness only affects one of these factors (focal length) so it doesn't necessarily mean a thicker lens is better overall. Try asking your wife/girlfriend if thicker always means better!

If that still doesn't make sense then just ask.

Humpers

Humpers
Posts: 82
Joined: 25 Aug 2012, 08:08
Location: Surrey

Re: Intro to aspheric lenses (to help you choose the best on

Post by Humpers » 26 Jan 2013, 16:04

terry1001 wrote:I tried doing this using a Sony camera doubler lens in front of a 501b with dx lens etc but only inside the house and there did seem to be a significant improvement in the beam. It was only a brief and not very careful experiment but did show some promise but as I don't feel the need for more range at present I didn't go any further, it's just an idea for the future.
Hmm, interesting again. How was the beam improved? Brighter/tighter/other? I can see I'm going to have to try it.

I'm not familiar with camera doublers, so are they aspheric lenses?

johnnyrebel
Posts: 229
Joined: 11 Dec 2012, 21:47
Location: sheffield

Re: Intro to aspheric lenses (to help you choose the best on

Post by johnnyrebel » 26 Jan 2013, 16:58

Hi Humpers,
i wasn't suggesting that the laser with aspherics wouldn't work, just that i didn't get what i was looking for when i had a play around with them, and didn't notice any difference from the focusing on the laser. That being said , i hadn't removed the lens on the laser as i was still using it at the time and didn't want to add it to this ever increasing pile of expensive " also rans" that i seem to be collecting!. As for now though it is redundant and after reading through this thread for the last week or so, it seems to have sparked a bit of interest up again. I think i'll have a mess around with them later in the week and contact one or two of the lads from the club to see how they went on with them. I must admit the watec really made a significant difference to my nv set up, i'm seeing as far now without illumination as i was with it before!. I had tried an ledengin behind a 28mm aspheric which was loads better than the laser i was using (5mw i think?) but these oslon blacks are a different ball game altogether. Thanks for the inspiration........ going shopping again now!

john :idea:
i'd give my right arm to be ambidextrous

User avatar
some bloke
TRADER MEMBER
Posts: 7547
Joined: 27 Jan 2012, 16:14
Location: Cornwall or Leicester

Re: Intro to aspheric lenses (to help you choose the best on

Post by some bloke » 26 Jan 2013, 17:56

Thanks for that explanation Humpers me old fruit. :thumbup:
Image

terry1001
Posts: 981
Joined: 27 Aug 2012, 09:30
Location: Ipswich, Suffolk

Re: Intro to aspheric lenses (to help you choose the best on

Post by terry1001 » 26 Jan 2013, 18:26

Humpers wrote:
terry1001 wrote:I tried doing this using a Sony camera doubler lens in front of a 501b with dx lens etc but only inside the house and there did seem to be a significant improvement in the beam. It was only a brief and not very careful experiment but did show some promise but as I don't feel the need for more range at present I didn't go any further, it's just an idea for the future.
Hmm, interesting again. How was the beam improved? Brighter/tighter/other? I can see I'm going to have to try it.

I'm not familiar with camera doublers, so are they aspheric lenses?
The beam was tighter, better defined and brighter but this was only a quick test indoors although I would expect it to work as well outside. The doubler lenses are a group of different lenses assembled into a single housing, like this one http://www.ebay.co.uk/itm/37mm-37-mm-2- ... 43a0f1eceb. They do come in various forms, some fit specific cameras and usually fit between the body and normal lens and others (like this) screw into the filter thread of the lens. They will need to be at the correct distance from the first lens to get the best results. I presume that this is the type of thing fitted to the pulsar 550 and 750. I have used them on some cameras with quite good results. It's probably worth a try if you are trying for the ultimate range and can pick one up at a sensible price.

User avatar
some bloke
TRADER MEMBER
Posts: 7547
Joined: 27 Jan 2012, 16:14
Location: Cornwall or Leicester

Re: Intro to aspheric lenses (to help you choose the best on

Post by some bloke » 21 Feb 2013, 07:33

Bump.

Could this be put into the DIY illumination stickies please to make it easier to find?

Has anyone got all the details of the 'sunnydlight' or whatever basic host to add to humpers list?
http://nightvisionforumuk.com/viewtopic.php?f=31&t=1955

At 38mm ish - It sits quite nicely between the small torches and the biggies.
Image

Locked