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Filter - UV or not? (1 Viewer)

Mike Johnston

Well-known member
I want to put a good B+W filter on my scope, mainly for protection. Is there ANY optical advantage in using a UV filter over a plain glass protective one? Thanks.
 

SPOTTED FLYCATCHER

Well-known member
Hi Mike,

I use a Hoya SMC UV filter on my Opticron Hr80 scope and I do find that it cuts down heat haze, giving me a clearer image at higher magnifications.

Steve
 

The Kerreran

Has hat, will stand in the rain
I want to put a good B+W filter on my scope, mainly for protection. Is there ANY optical advantage in using a UV filter over a plain glass protective one? Thanks.

Hi Mike,
I use Hama HTMC UV filters on both my Nikons [ED82 & ED50] - and like Steve I find they help with heat haze a little, and also cut glare; thus giving a much 'easier' view on the eyes. Looking at waders on wet mud, or seawatching into the light, it's a definite advantage. There is [inevitably, with 2 extra glass/air interfaces] a little light loss - so I'd advise that you buy the best filter you can to minimise that. I doubt there'd be any real difference in light loss between UV and plain glass of similar quality though [possibly with good coatings a high-end UV may even be better?].
 

hollis_f

Well-known member
Hi Mike,

I use a Hoya SMC UV filter on my Opticron Hr80 scope and I do find that it cuts down heat haze

Really? But that's physically impossible. Heat haze is caused by hot air rising from the ground. The different densities of the rising hot air and the surrounding cool air cause differences in the refractive index which makes the visible light 'wobble'. Just filtering out the UV can't change that.

Some people believe that a UV filter can cut down the blue haze you get when photographing long-distance landscapes. That was true in the days of film, which is sensitive to UV light. But digital cameras aren't - nor are our eyes. So a UV filter should have zero positive effect on anything you can see.
 
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SPOTTED FLYCATCHER

Well-known member
Hi Mike,

Perhaps is dosen't 'technically' and specifically reduce the effects of heat haze, but the UV filter certainly seems to improve the image quality at higher mags. There is a very very small amount a light loss but the improved image quality gives as 'the Kerreran' says, a more relaxed view.

Steve
 

The Kerreran

Has hat, will stand in the rain
Really? But that's physically impossible. Heat haze is caused by hot air rising from the ground. The different densities of the rising hot air and the surrounding cool air cause differences in the refractive index which makes the visible light 'wobble'. Just filtering out the UV can't change that.

And yet the evidence of our eyes is that a UV filter has a small but definitely present effect. I'm not a physicist, I can't explain it, I only know it's there. To my [perhaps freakishly odd?!?] eyes, the quality of the optics you're looking through has a larger effect - comparing my ED82 with a Kowa 883 made me a little envious - but even then it is only a small percentage improvement, against what is not really 'serious' haze. Maybe one of Birdforum's resident optical experts can enlighten us?

Some people believe that a UV filter can cut down the blue haze you get when photographing long-distance landscapes. That was true in the days of film, which is sensitive to UV light. But digital cameras aren't - nor are our eyes. So a UV filter should have zero positive effect on anything you can see.

Except our eyes are affected by UV light - we just can't 'see' it. As I said before, a UV filter helps to counteract eyestrain, and this is the chief [after protecting your expensive objective lens] reason for using one. Photographers looking at digital images naturally needn't be bothered.. ;)
 

hollis_f

Well-known member
Well, I happen to have a UV filter in front of me.......


Nope, the world looks exactly the same through the filter as it does without.
 

Birdbrain

busy doin nothing
United Kingdom
Tom

Where did you get your Hama HTMC UV filter from ?
It would be for my ED50 ?
Can you put a link on here for me ?

Thanks Buddy
 

The Kerreran

Has hat, will stand in the rain
Steve,

Got mine from Amazon. A search for something along the lines of "Hama HTMC UV filter 55mm" in their electronics and photo section should do the trick! :t:
 

Kevin Purcell

Well-known member
As others have said the UV filter does nothing for the human eye. But it may help protect the objective.

It was handy for flim (which would haze up with near UV).

Most of the UV is not going to make it through the optics of the scope: the glass is opaque to the UV even more so than camera lenses (more elements and a couple of prisms).

And the only way it can affect the eye is by stimulating a receptor (the S or blue cones) so you will "see" it if you could see it.

It can't fix "heat haze" that's an effect of refraction in the air which is jumbling light rays. You have to spend a lot of money on adaptive optics to undo that effect.

A poor UV filter might reduce light through put through the scope (and that cuts down on glare) but you get perhaps a better effect with a neutral density filter (pick the density that works best).

Or even better, especially for sea watching, a polarizing filter.

If you are using a non-roof prism scope then sunglasses work well too if you want to cut down the light (especially water reflected light and polarized sunglasses).
 

npos

Well-known member
I want to put a good B+W filter on my scope, mainly for protection. .

I use a B+W easy-to-clean UV as a protective plate over the objective in bad weather conditions. In that regard clear vs. UV does not really matter, though your choice of a high quality filter such as the B+W is a good one because you won't degrade the optical quality you've got.

NP
 

kristoffer

Used Register
Is it not a problem that moist can accumulate behind the UV-filter and causing fog when you are out birding? Since it is not watertight.
 

etudiant

Registered User
Supporter
Moisture condensing inside the filters has certainly been an annoyance, particularly as it happens gradually, so the image degrades unexpectedly, just when a good bird is coming into view. Maybe wiping the filters with an anti condensation cloth would help, but it may affect the image.
Has anyone found a real world solution?
 

BobinKy

Well-known member
When I used to do nature photography, I would carry two or three extra UV filters in my filter case. I was always getting dust or mud on the filter (outside glass), so I would change them in the field when they became dirty. After I got home, I would clean the dirty filters and get ready for the next outing.

If the condensation forms on the inside of the UV filter, but not on the objective lens, carrying an extra UV filter in the kit might help.
 

Fernando np

Well-known member
Altough I don't use UV filter the advantage is evident, in the Zeiss 85, round midday in full light. The binoculars FLs, with the same whitish bias probably would get same gains with filters.
 

jaymoynihan

Corvus brachyrhynchos watcher
I attached avery good one to my objective end with plastic tape (no filter threads). Did it to protect the glass, had it on for years. Now i have it off and using one of those flip-up covers made for large rifle-scopes. No difference in the view noticed.
 

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