Reflections in a sinar sinaron se f5.6 150 mm

[luis-LF]

Hello to all,

I am starting to build my 4x5 equipment. I am a newbie to large format and would like to ask your advice on this problem I am having.

I bought a Sinar Sinaron SE F5.6 150mm. The description says that the glass is in "excellent condition".

However, when I do the "Flashlight Test" I can see very small reflections (see pictures) in one of the front elements that look crystal-like. The seller tells me that this has "no effect on the quality of the pictures in anyway".

I have never seen this defect before and have no experience to judge if this is a serious problem that will affect the quality of my pictures.

Does anyone have experience with this and can tell me what the issue is? Thanks a lot!

Luis


PS https://www.kenrockwell.com/tech/flashlight-test.htm

[Oslolens]

Looks like fungus/fungi to me. Google it to compare.

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[luis-LF]

KenRockwell.com. indicates that "Fungus shows up like wildfire in a flashlight test. Fungus looks like little soft dots, usually white, sometimes fluffy, when you look into a lens in normal light."

The spots of this lens looks like tiny brilliant dots. Only seen when light hits them indirectly. There is no filaments. The seller indicates that this is the decay of the coating of the special ED element. He says that "the coating layers are sprayed in layers, which contain rare metals"...

I am wondering if someone has seen something like that before.

[Oslolens]

Put black velvet around the back of the lens and use a digital kamera in the back. The resolution will be lower than your average digital lens up to f16, but the contrast should be equal with a good sun shade and with the black velvet not lit up with by the sun. See if the results is acceptable for you.

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[ic-racer]

Sometimes that wipes off...sometimes not.

[Bernice Loui]

Could be dust or similar dirt particles. Could try un-screwing the lens cells from the shutter, blow off the particles then wet clean with the proper lens cleaner.

Do NOT use one of those micro fiber "lens wipes". If the particles are abrasive, the wipe will grind those particles into the optical glass, might be no problem, might cause damage to the coating and optical glass. Just depends on what the particles might be.

No, ED glass or modern coatings do not "decay" ED glass goes back decades before Rodenstock used in in this series of their LF lenses.

BTW, anti-reflection coatings are Sputtered on. Sputtering is done in a high vacuum chamber with the material to be applied turned into a violently energetic plasma (ions) which essentially impales these particles into the surface being sputtered (in this case optical glass). Does not come off easy at all once properly done and the materials used in modern AR coatings will be very long term stable.

Will this dust-dirt have a serious affect on images, not likely much if at all.


Bernice