melles griot / cvi ashperical lens produce unsharp edges - why?

[mash.m]

hi,

last week i ordered the 01lag123 lens 37mm focal lenght with coating at cvi to compare with the kaidomain lens. but the cvi lens produce a unshapren "corona" outside the led die:

sorry for the white balance.

any ideas why this happen?

if the head is screwed completley in, the melles lens produce the better beam, without any shade.

markus

 

[mash.m]

and defocused the cvi lens produce the better spot without any hotspot or shadow:

markus

 

[LukeA]

The MG lens is more precisely formed. It doesn't view the whole 3mm*3mm in focus the way the KD lens does. The evidence for this is the differences in the crosshairs between the dies. The crosshairs on the MG lens is darker and smaller than the KD lens.

 

[DocD]

Take a look at the under side of the lens the KD is slightly dome and maybe the melles griot is not this would explain the two diffrent images cheers DocD

 

[65535]

Looks to me like the focal point is tighter than the KD a more precision lens. Normally that is a good thing, but it does bring flaws or anomalies into the picture that are normally blurred out.

 

[LuxLuthor]

First, I see that Melles Griot has merged with CVI Laser and has a whole new website and part number system. The new part number without anti-reflective coating is LAG-52.0-37.0-C on this web page. With the AR coating it is part number LAG-52.0-37.0-C-SLMF-400-700

Several issues are illustrated here.

• First these aspherics do best with single die LED, such as those used by Saabluster in his DEFT, or those used by Mac & Ledean. Some of the differences and rings you are seeing are due to the interaction of the die against each other, and with none in the exact center of lens.

• Second, there is a significant difference in the quality of the glass, with MG being the highest standard. That is the greatest difference in performance, with a slight variation in focal length & shaping in KD lens being a secondary issue.

• Third, adding the AR will likely increase the off center multi-die LED reflections within the glass, resulting in your brown halo. If you look at the large view of the first image in the above Mac & Ledean linked thread, you will see a slight halo on white wall with these LED's.

• Fourth, I do not know if you are using a reflector, but none of my aspherics use one, and they do better without.

 

[mash.m]

thanks to all for your answers.

@luxluthor:
there is no reflector - of course.

last night (bevor you postet i testet with a single die emitter, and you are right the halo is minimized.

i think i will use the cvi lens, cause it have the better build quality and makes a perfect defocused spot.

@all other that will think about to use this lens. this lens do not fit without modifying the mag head!

markus

 

[LuxLuthor]

Markus, if you act now you can get in on the 2nd round of longer bezels that will allow you to use that lens without any adjustments. You can see I was very happy with it....even promoted it in my Mac Ledean Aspheric review thread.

A whole bunch of us tried different focal length aspherics, and different LED emitters, including the MC-E, so if you can look up those old threads you will see all this was tested and reported on previously. The Melles Griot lens used to be available from www.SurplusShed.com at a low price of like $8 until they ran out.

Here are a couple of those older threads:

http://www.candlepowerforums.com/vb/showthread.php?t=175386
http://www.candlepowerforums.com/vb/showthread.php?t=161748