# Fake UV filters?



## duydaniel (Jul 24, 2013)

This:
https://www.youtube.com/watch?v=OfAwd_8aklE


Even Canon selling us fake UV filters?
Look like Zeiss is the only legit one. 
I wonder what about B+W since I am using them

If anyone has the uv flash light, can you test with the B+W?


----------



## Jim Saunders (Jul 24, 2013)

If no-one gets back to you in the meantime I have a B+W UV filter here and an enormously powerful UV light at home; I'll try it. I know off the top of my head that when I tried it with one which may or may not have been B+W the UV portion was thoroughly cut.

Jim


----------



## expatinasia (Jul 24, 2013)

There is very little reason to test one product of a brand. I am sure there are fake versions of pretty much everything, including cameras. I even read that there fake components (albeit still expertly manufactured) in many airplanes, cars, ships. Even food, just look at the recent horse meat issue in England!

We all try to reduce this risk by buying from more reputable dealers. But even then who knows whether a fake box with hundreds of fake filters, was swapped with a real box with real filters in it. Overruns like they have at clothing factories (where a small error is accidentally/purposefully made, but cannot be sold by the brand) have to go somewhere, and while some surely do get destroyed I know in my part of the world there are hundreds of clothing shops that sell original clothing at a very small fraction of what they would cost if they weren't overruns, and I am positive this happens in other industries, it is just more common to hear of someone selling L***oste shirts or R***x watches than it is camera lens filters... ;-)


----------



## neuroanatomist (Jul 24, 2013)

It's not about 'fake' - it's about transmission curves. 

Can't speak for the 'Rocketfish' or Canon, but Hoya, Zeiss, and B+W all publish their transmission curves. No filter has a perfectly vertical cutoff on a transmission curve - most good commercial multicoated filters that 'block' wavelengths ramp from ~0% transmission to their max of >99% over a 25-125 nm range (although some of the longpass and bandpass filters I use in microscopy are close to vertical, with a slope covering <5 nm - and they come with a price tag commensurate with that performance). 

The Zeiss has the steepest slope of the three, ramping up over the 410-435 nm range (in fact, it's cutting out some blue light, which is considered to start at 400 nm). The Hoya has the least steep slope, running from 350-460 nm or so, meaning its passing some UV in the 350-399 nm range, and blocking a bit of blue light as well. The B+W is intermediate, ramping up from 360-430 nm. 

So, with the '395 nm flashlight' (which actually uses an LED that emits at 380-385 nm, but what's 10-15 nm among friends?), you can see from the transmission curves that the Zeiss will block that, while the Hoya and the B+W filters will pass some of it. 

Of course, while that might be good to know if you're shooting film, none of that matters if you've got a dSLR. The dSLR's sensor is insensitive to UV light, so there's no difference between a UV filter (be it the 410 nm Zeiss or the 360 nm B+W) and a clear filter that fully passes the long end of the UV spectrum. I have empirically tested my 7D and 5DII for UV sensitivity with calibrated UV/Vis light sources (costing a hell of a lot more $$ than a flashlight to detect cat urine!) and some of those precise bandpass filters mentioned above (running a lab that has such equipment comes in handy sometimes) - there's no need for a UV filter. I do use UV filters for protection (B+W MRC or Nano), instead of clear - but that's only because every time I've needed to buy one, the UV version was cheaper than the clear one (although that's not the case with all brands or in all geographies). 

So, my advice is to just buy whichever is cheaper, clear or UV. I'd still pass on the Hoya - it blocks a bit too much blue (and that's the least sensitive color channel). Since it blocks less of the visible blue light, the B+W is actually a bit better than the Zeiss in that regard (because sometimes 5-10 nm _does_ matter among friends).


----------



## Jim Saunders (Jul 24, 2013)

...Here we see the difference between modestly-equipped speculation, and science. Good times.

Jim


----------



## weixing (Jul 24, 2013)

neuroanatomist said:


> It's not about 'fake' - it's about transmission curves.
> 
> Can't speak for the 'Rocketfish' or Canon, but Hoya, Zeiss, and B+W all publish their transmission curves. No filter has a perfectly vertical cutoff on a transmission curve - most good commercial multicoated filters that 'block' wavelengths ramp from ~0% transmission to their max of >99% over a 25-125 nm range (although some of the longpass and bandpass filters I use in microscopy are close to vertical, with a slope covering <5 nm - and they come with a price tag commensurate with that performance).
> 
> ...


 +1. If you do Astronomy, you'll know that different brand filter had slightly different transmission curve even they are the same type of filter... you had to look at the transmission curve.

Anyway, I found a website that had publish some UV filters test result with transmission and absorption curve:
https://ww2.chemistry.gatech.edu/~nmakarov3/INTERESTS/Photo_Filters/index.htm

Interesting to see the EF 50mm 1.4 lens also block UV light...

Have a nice day.


----------



## scottkinfw (Jul 24, 2013)

Well said.



neuroanatomist said:


> It's not about 'fake' - it's about transmission curves.
> 
> Can't speak for the 'Rocketfish' or Canon, but Hoya, Zeiss, and B+W all publish their transmission curves. No filter has a perfectly vertical cutoff on a transmission curve - most good commercial multicoated filters that 'block' wavelengths ramp from ~0% transmission to their max of >99% over a 25-125 nm range (although some of the longpass and bandpass filters I use in microscopy are close to vertical, with a slope covering <5 nm - and they come with a price tag commensurate with that performance).
> 
> ...


----------



## neuroanatomist (Jul 24, 2013)

weixing said:


> Anyway, I found a website that had publish some UV filters test result with transmission and absorption curve:
> https://ww2.chemistry.gatech.edu/~nmakarov3/INTERESTS/Photo_Filters/index.htm
> 
> Interesting to see the EF 50mm 1.4 lens also block UV light...



IIRC, Lenstip also tested transmission of many UV filters with a spectrophotometer. 

It's interesting that the 50/1.4 blocks some UV, but not surprising. Standard microscope objective lenses don't transmit UV all that well, so for applications with UV fluorophores, we use objectives specifically designed for better transmission down to ~340 nm.


----------

