Blackmagic Forum

Hello
What order should the filters be in?
LENS-IRUV-DIFFUSION-ND?

As long as they are in front of the lens it doesn't matter as they are all passive devices. Maybe there is a case for the filter with the best anti reflection coating going on the front and also a case for not using IR filtration unless absolutely necessary.

Test it, see what you like best. I’ve noticed a difference in the look based on the order, especially using diffusion filters.

Que Thompson wrote:Test it, see what you like best. I’ve noticed a difference in the look based on the order, especially using diffusion filters.

With a diffusion filter the distance from the lens will definitely change it’s effect but not the order itself.

If you use a hot mirror type of IR cut filter, it should be placed as far from the lens as possible, on top of the stack.

There's a guy on Reddit that seems pretty knowledgeable about most things in this area. Both he and his wife are Camera Assistants working in Vancouver's film industry Here are couple of posts he made on 6/5/21:

u/near-far-invoice said:

"...It is NOT the order. It's better to have the diffusion closer to the lens, yes, this order is backwards. But that's NOT what causes the double image."

I placed an ND filter on top of the lens and then placed a pro mist on top of that. I realized there were some ghosting happening(double imagine) in the image especially for white wardrobe. Was the order of the filters causing this? I used donut ring so no light could be coming ' from the back'.

https://www.reddit.com/r/cinematography ... nt/h0otdw3

near-far-invoice said:

"Diffusion always closer to the lens."

Will a 58mm Tiffen ND filter thread onto a 58mm Tiffen Black Pro Mist 1/4 filter? And do you put the pro mist or ND on the lens first?

https://www.reddit.com/r/Filmmakers/com ... nt/h0ou137

The RED One camera was notorious for having poor IR filtration and needed an IR cut filter. I found this in my notes from 2008:

Pawel Achtel said "...The IR cut should always come first, not last. This is because IR will go through all of your NDs and bounce back from IR cut filter causing flare and reflections in IR spectrum."

Hot Mirror/IRND/Mirror ND Filter Matrix [Parts 1-4]

http://www.reduser.net/forum/showthread ... -1-4/page7

That applies to the hot mirror IR filters. The ones which are just blocking IR might simply get hot if not ventilated.

Uli Plank wrote:That applies to the hot mirror IR filters. The ones which are just blocking IR might simply get hot if not ventilated.

Uri, in the post, Pawel responded to this:

"Originally Posted by First Light Films View Post

I'm using the B+W IR cut filter - It comes in a 77 mm circular, which I mount on the lens. the NDs and pola go in the matte box. Any opinions on this set up?"

So you're saying that he is mis-interpreting the operation of an IR cut filter as a Hot Mirror filter?

In my imagination, I was thinking that he was telling us that some visible near infrared light was reflecting around in the filter stack and flaring, possibly defeating the purpose of the IR cut filter a little due to it's placement, especially with old lenses that are not multi-coated.

It's a shame that the post is so old, maybe we could ask him directly what he meant.

That is interesting what you said about IR cut filter ventilation. Could IR heat cause an IR cut filter to fog up if it was not on the end?

dondidnod wrote:That is interesting what you said about IR cut filter ventilation. Could IR heat cause an IR cut filter to fog up if it was not on the end?

Funny, I just had this happen to me today. Though not just from heat. I screwed the IR Cut on the lens, stuck my greasy finger tip in the middle of it. Took it off, washed it – yeah, controversial perhaps, but the gentlest way I've found to clean filters is: lather with hand dishwashing liquid and rinse with plenty of running water, dry with a lens blower (I'm open to suggestions ). I put the ND in front of the IR Cut. Went outside, 27°C. Was wondering where all the flares are coming from, and it just got worse every minute. Finally realised, there was still some moisture probably in the filter glass to rim seam and it was fogging up in the heat. Luckily the heat also dissipated the fog quickly when I unscrewed the filters.

Ordinary water is not free of residue, like some minerals. I'd use medical grade alcohol or isopropanol and one of the small sticks with a tip of soft leather. Alcohol will get off the grease from fingerprints without any detergent, which might also leave some residue.

Uli Plank wrote:Ordinary water is not free of residue, like some minerals. I'd use medical grade alcohol or isopropanol and one of the small sticks with a tip of soft leather. Alcohol will get off the grease from fingerprints without any detergent, which might also leave some residue.

Thanks Uli, for the suggestions!

I use isopropanol when cleaning lenses, which obviously can't be submerged. I swipe the surface with a cotton swab dipped in the alcohol and with a lens cleaning paper between. I switch to a new clean part of the swab and paper frequently. Still it often seems like its just moving the streaks around and takes five or more swabs and papers to clean one lens surface. What are these leather tipped sticks that you mention?

If the filter has a good water repellant coating it pretty much runs itself clean and dry by itself after my lather-and-rinse-method. Good point about the minerals in tap water, maybe I should at least switch to distilled water.

The probability of double reflections and ghosting, arising owing to point reflections of bright light sources, increases with increasing number of filter surfaces in front of the lens. And these reflections tend to be more prominent when using prime lenses than zooms, especially with apertures wider than T2.8.

In my experience, the screw-in diffusion filters by Schneider appear to produce more ghosting flares than do those by Tiffen.

If you’re stacking filters, then DIFFUSION–>IRUV–>ND may be all right. However, even if all these filters have anti-reflective coatings, there will likely be ghosting and double reflections simply because the light has several surfaces between which it can bounce.

The only way to minimize these reflections is to use not more than 2 filters at a time. Alternatively, one can use one of those matte boxes with tiltable filter-holders.

It would make sense to have the IR cut filter closest to the lens since the other filters will be the ones that will be changed to taste.
Not only that but the IR cut filter is there for the purpose of removing IR possibly introduced by any other filter that is being used at the time.
LENS>IR CUT>OTHER FILTERS

Leon Benzakein wrote:It would make sense to have the IR cut filter closest to the lens since the other filters will be the ones that will be changed to taste.
Not only that but the IR cut filter is there for the purpose of removing IR possibly introduced by any other filter that is being used at the time.
LENS>IR CUT>OTHER FILTERS

How can a filter introduce IR?