64mm and 70mm filters

[Doc W]

I just got a 250mm Fujinon W f/6.7. I like to have protective filters - front and back - on all my lenses but the filter sizes are 64mm and 70mm! Talk about a rare bird. I could get by just using a lens cap on the rear but I really would like a protective filter for the front. I would also like to be able to use my 77mm filters. I am thinking of getting a machinist to make a 70mm to 77mm step up ring but I bet that won't be cheap.

Any ideas?

 

[Doc W]

UPDATE: it looks like the number on the lens cap was NOT the thread size. The lens cap for the front element said 70mm but is in fact 67mm (thanks, Ari) which means I can use my step-up ring. That leaves the rear element but I am going to find out exactly what the size is before I make any further rash judgements.

 

[Doremus Scudder]

If you have lens caps, you really don't need "protective" filters. They don't protect any better than a lens cap and the four extra air-to-glass surfaces will degrade your images somewhat. Use filters when you need them and avoid them when you don't for best image contrast and quality. My lenses all have front and rear caps that get removed only when the lens is mounted on the camera. The rear element is more than adequately protected inside the camera; the front gets a protective filter when water or sea spray is a danger. However, these latter are of more danger to the shutter than the lens itself anyway. Lens glass cleans up easily after exposure to sea spray; it's much harder to clean the shutter and other exposed metal parts that corrode easily when exposed to salt.

And, a "protective" filter is more likely to break and damage a lens element when the lens is dropped (heaven forbid) than a lens cap.

Best,

Doremus

 

[Doc W]

Thanks, Doremus. I have often wondered about this. I am a clumsy person and I did drop a lens (once and once only!). It survived but was quite bent. Perhaps I am now over-compensating.

I was of the opinion that high quality protective filters would not degrade the image at all. I guess all I really need to do is make a few tests, with and without protective filters.

 

[John Koehrer]

With decent filters image degradation is mostly theoretical not visual to 90% pr better of people.

 

[jim10219]

I wouldn't worry about losing image quality with a filter. But I also don't think they'd provide any extra protection on a large format camera. On a 35mm, where you might be hand holding the camera while running through brush, it could come in handy. But since you don't generally shoot LF handheld, a lens cap usually works just as well. The only time you should have the lens cap off is when the camera is secured on top of a tripod. And if it falls over then, a filter isn't likely to do much other than shatter and throw shards at the coating.

 

[Doremus Scudder]

With decent filters image degradation is mostly theoretical not visual to 90% pr better of people.

I agree; the slight degradation introduced by adding two filters will likely not be visible to most and could easily be compensated for by exposing a bit more and printing a bit contrastier. However, lens caps are a heck of a lot cheaper than high quality filters that are really not doing much good if protecting the lens is their only function. Plus, you have to remove the front filter to mount other contrast filters (unless you want to stack them on top of the protective filter), which seems fiddlier to me than just mounting and removing a filter when needed. So, it's cheaper and less clumsy to not use filters. I don't really thing having a filter on will be much help if you drop a lens either, and there's always the danger of the filter breaking and damaging a lens element if a lens is dropped. If there's no filter mounted, you might get by with just a bent filter ring.

Best,

Doremus

 

[Jim Noel]

Having a filter on a lens to protect if dropped makes no sense. If the lens is dropped, or hit, the filter will probably be broken and fragments may scratch the lens.

 

[Doc W]

All good arguments. I just saved myself a pile of money. I love APUG!

 

[bdial]

For drop protection, a lens hood probably makes more sense. Plus, it will help reduce flare when the lens is in use, which a filter cannot do.