Asahi Super Takumar 135 f:3,5

[photoni]

I don't like long focal lengths, but I bought this Asahi Super Takumar 135 f3.5 at a good price

It should be the 2nd version. LINK

I thought I was lucky, a simple scheme with four separate lenses, and no SMC.

Before using it, I checked its transparency with the diffraction grating.

Unfortunately it is not as good as the Meritar 50mm, or the two Astron (which however do not have a thread for the filters)

The comparison test are at the same distance with flash light and fluorescent light,

using the emission peaks as a measure.

(I discovered that these lights are no longer for sale in Europe and have been banned because they contain mercury)

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[Andrea B.]

Tony, you will get some good use from this Asahi 135/3.5. 

It might not transmit as much UV as the Meritar, but it's certainly good in a nice range around 365nm.

 

Una domanda, per favore:  Non ricordo come usi il "diffraction grating" per effettuare le misure?

Is the diffraction grating in a filter ring?

How do you produce the black background shown above?

I recently bought some new diffraction grating material and would like to try this kind of measurement myself.

 

 

[photoni]

16 hours ago, Andrea B. said:

Tony, you will get some good use from this Asahi 135/3.5. 

It might not transmit as much UV as the Meritar, but it's certainly good in a nice range around 365nm.

 

Yes, I believe that researching the depth of UV is useless with my cheap filters.
Using ZWB1 (~ UG11) + TSN575 or QB39 3mm (~ BG39)
all light is cut below 350 nm

[photoni]

On 8/30/2022 at 8:30 PM, Andrea B. said:

Una domanda, per favore:  Non ricordo come usi il "diffraction grating" per effettuare le misure?

Is the diffraction grating in a filter ring?

How do you produce the black background shown above?

I recently bought some new diffraction grating material and would like to try this kind of measurement myself.

 

I used an old flash lamp with a very wide tube, in the middle it has a standard E27 socket I can put a "quartz" or "fluorescent" or "wood" light
then I use a 70cm black paper tube that ends with a lens hood for 52 diameter lenses, where I change the filters (I don't put them on the camera)
at 20 cm from the tube I put a 1mm chromed steel wire
I photograph the chrome wire from the side at 90 degrees.
the backdrop is black cardboard
the diffraction grating can be close to the camera, or if it is large at an intermediate distance from the wire

 

 

[Andrea B.]

Grazie mille! I appreciate your taking the time to illustrate your method. It will be useful to many of us.