Hoya U 340 vs 360?

[Doug A]

Read that U 360 is good to 350nm. My camera, Igoriginal 35 and El-Nikkors go to 330nm. Should I be considering U 340 instead (with S8612)?

 

Thanks,

Doug A

[ulf]

1 hour ago, Doug A said:

Read that U 360 is good to 350nm. My camera, Igoriginal 35 and El-Nikkors go to 330nm. Should I be considering U 340 instead (with S8612)?

 

Thanks,

Doug A

Even if your camera reach 330nm it is dramatically less sensitive there.

The U-360 stack is still a pure UV-stack and the visual difference to a U-340 is not dramatic.

You will mostly loose in exposure time with the U-340 as it peaks further down in UV.

 

IMHO the U-360-stack is the optimal one. 

[Andy Perrin]

I think so too. Sadly the camera gain falls so fast past 350 that it’s like hitting a wall. It’s true that you can bash through a wall if you push hard enough, but sensible people who just want ordinary UV photos and aren’t trying to push their equipment to the limits (where it doesn’t perform very well) probably shouldn’t. 
 

Sooner or later you probably WILL try your luck with that wall, cause everybody does, but what you will find is that below 350nm you have less and less light to work with, and the camera acts like an old man with cataracts, and you start to find light leaks that you never knew existed in your camera body, and the infrared and visible light contamination that you THOUGHT you’d conquered are back again because now even OD5 blocking is not enough when the light is so dim and your poor straining camera is half blind. 

[Doug A]

@ulfand @Andy Perrinthanks. Got excited when a Hoya 52mm U 340 showed up for sale. Now I know why. I don't need more light leaks or flare. Still fighting the new helicoid for El-Nikkor 135. Causes hotspot that isn't there with bellows. Don't even get me started on M42 adapters.

 

Thanks, trying to be patient,

Doug A

[dabateman]

The U360 gives a bluer image than the U340, which is more yellowish.  If you like that than its ok. I like a more golden image.

U340 filters like zwb1 are good for led lights to keep everything below 400nm.

To get down lower you need custom lighting.  340nm leds are still too expensive and the 335nm Mercury lines isn't nearly as strong as the 365nm or even 313nm lines.

If you have a special 340bp or 335bp filter stacked with u340 to block the IR leakage,  than you can get the 335nm line out a blb compact fluorescent bulb.

But I don't think you want to go there. So you might just be happy with U360. 

 

Something else to consider would be a U330/UG5 filter. It gives you a green UV pattern look in color,  but looks the usual way in monochrome.  Thats a way to squeeze out some extra stops if you are only converting to monochrome. 

 

[Doug A]

Thanks @dabatemanfor the reply. Just noticed the filter is 3mm thick. It is a strange one, probably too specialized for my needs.

 

Thanks,

Doug A

[ulf]

I have a set of two even thicker U-340, I got from Cadmium, both 4mm thick.

These two stacked to make a 8mm thick U-340 stack creates an interesting UV-pass filter that do not need any BG-glass.

The stack eliminates the upper UV-A while still having a reasonable transmission.

The final result is more dependant on how the camera sensor's sensitivity is tapering off in the shorter wavelengths.

I have not yet had the opportunity to test it much, but some time in the future I hope to use it more.

I used it for this image:

 

 

Later I confirmed that the yellow sky is typical for WB against PTFE too.

At this time of the year there is no flowers. 

 

I hope to get really interesting images with closeups of flowers in the future.

[ulf]

 

[Cadmium]

Myself, I use U-360. U-340 (or UG11) is better for filtering light, torches, flash, because it cuts off more of the 400- range.