Center filter order with 6x17

[Dilznik]

Hi,

The Schneider site says you should put the center filter on first and then any filters after that. This pretty much leaves you with no choice but to get a Cokin X-Pro type system. I only want one extra filter at a time and 82mm is an easy size to get filters for. Is it really necessary to put the center filter first or would it not matter?
Also, would there be vignetting?

This is for a Linhof Technorama with the 90mm fixed lens (first version).

[Bob Salomon]

It is very important for the center filter to be mounted directly to the lens. That is why the instructions tell you to do so.

Also, to make sure, for the center filter to work the lens MUST be stopped down at least 2 stops from wide open. So you must shoot at at least f11.

You aren't limited to Cokin. Any quality slim 82mm filter like the ones from Heliopan and Rodenstock will not vignette on the CF.

[Lachlan 717]

I mount a Pol filter to the lens and then the CF on my 6x17cm and have no idea why it is "very important for the center filter to be mounted directly to the lens". My images seem okay to me. I'd be interested to find out why it's allegedly so important not to do it this way.

[SMBooth]

Ill would say the further away the filter is the more severe the graduation. How much 5mm much I don't know.

[hoffner]

I mount a Pol filter to the lens and then the CF on my 6x17cm and have no idea why it is "very important for the center filter to be mounted directly to the lens". My images seem okay to me. I'd be interested to find out why it's allegedly so important not to do it this way.

Bob Salomon is right. The distance of the CF from the lens changes the angle of the rays that hit the lens after passing through the CF.

[Emmanuel BIGLER]

The distance of the CF from the lens changes the angle of the rays that hit the lens after passing through the CF.

I would say things differently but the consequences are identical.
The important reference point is the centre of the entrance pupil and when the lens is stopped down as it should be for proper operation of the CF, the only rays to take into account are those aiming at the centre of the entrance pupil. So the ray tracing is extremely simple, it is a simple cone of rays at a given angle.
The CF is calibrated so that a certain angle in entrance has to go through a certain density at a certain place on the CF.
If you move the CF away from the entrance pupil, the same ray with the same angle will hit the CF further away from its center, hence the more pronounced compensating effect as mentioned by SM. Booth, since the filter is darker on its edges.

And even moving the filter further away from the lens you can get abrupt mechanical vignetting instead of a smooth graduation.
Those 90° to 120° ultra wide angle beasts are a challenge to our usual ideas regarding simple ray tracing in photography ;-)

[hoffner]

I agree, Emmanuel. It's like a ring through which the rays pass - the further away the ring is from the lens , the narrower is the angle of rays passing through it. It simply changes the effect wanted by the CF.

[Dilznik]

Thanks all.

Sorry, with Cokin I meant when I have the center filter on it goes from 82mm to 105mm. So any filter sets I get after that have to be for 105mm, which the x-pro does. I was hoping to get away with the 82mm Tiffen graduated ND screw on and then the CF after. Because I'm poor. And lazy.

[hoffner]

Of course, before you go for the CF you could just see for yourself if you ever need any. I have been using Technorama 617 (the same model you have) for ages and did not see any need of a CF for it.

[Lachlan 717]

Where theory and reality don't equate IMO. Perhaps I'm not priggish enough to notice the difference?

[hoffner]

Being priggish is one thing and not to understand a theory is another one. Take your pick.

[Lachlan 717]

And being too caught up in said theory to notice that it makes no discernible difference is yet another thing. Take your pick.

[hoffner]

Notice also, that not to understand a theory and being too caught up in thinking that it does not matter are also two different things. In this case your picks coincide.

[Lachlan 717]

Notice also, that not to understand a theory and being too caught up in thinking that it does not matter are also two different things. In this case your picks coincide.

The other option, of course is that I do understand the theory and it does, in fact, make no discernible difference, meaning that you're too caught up in erroneously and presumptuously hanging shit on my understanding of theory to realise that those who can, do, while those who can't sit and wax lyrical about theory. In this case, your picks coincide, Poindexter.

[hoffner]

Your understanding of theory? What understanding? That in your post n.3? Not so much to speak about, lyrically or not but enough to get "caught up in erroneously".

[Lachlan 717]

Your understanding of theory? What understanding? That in your post n.3? Not so much to speak about, lyrically or not but enough to get "caught up in erroneously".

You're not having a great day, are you? If you had taken the time to comprehend my comment in post #3, you would realise that I was questioning the claim of it being "very important" (which it isn't), not "what is the theory". You really, really need to get over your notion that I don't understand the theory if you're to continue trying to hang shit on me...

[hoffner]

I'd be interested to find out why it's allegedly so important not to do it this way.



You really, really need to get over your notion that I don't understand the theory if you're to continue trying to hang shit on me...

Looks like you understand and not in one and the same pick that became two. Masterly done.

[Lachlan 717]

Looks like you understand and not in one and the same pick that became two.

What I don't understand is your nonsensical use of English. I have no idea what this post means...

[Jeff Keller]

Interjecting a I don't understand:

Schneider makes center filters with different strengths for different lenses. Many of them have different thread sizes on opposite sides of the filter. If you don't use a Schneider center filter on a Schneider lens maybe the correct distance isn't mounted directly to the lens because the darkness and gradation weren't specific for that lens? If you are trying to mount a center filter which has different thread sizes further from the lens, you would almost surely cut down your image circle.

So if you have it try it and see if you like it ...
If you don't have it, load a scanned image into photoshop and find out how much gradation is perfect and how much is acceptable.

[Dilznik]

wtf happened to my thread?

Anyway, I have the Schneider one. I notice a difference without it. It's not terrible though and might even be useful. Maybe I'll try and bum an 82mm filter or two off someone and give it a try without the CF. Or just get a 100mm Singh Ray 2 stop grad and handhold it

[resurgance]

I have just been reading this post (well the first half anyway) having just bought a tecno 6x17 with fixed lens. It came with a center filter IV which i presume mates well with the 90mm SA. The optical details in this post make sense to me, but if that's the case, where do I get a gargantuan 105mm R72 filter to shoot IR with??
The 77mm Hoya I have been using with my 65mm Grandagon mounted on 6x12 that is for sale, post Linhof just got obsolete... (breath)

[resurgance]

Just out of interest, and I will try this when I hopefully take possession of an 8x10 enlarger, will the natural vignetting on an enlarged image (6x17 neg in 8x10 enlarger using 240mm process lens) counteract the in camera vignetting of an image taken minus CF?

[Bob Salomon]

Just out of interest, and I will try this when I hopefully take possession of an 8x10 enlarger, will the natural vignetting on an enlarged image (6x17 neg in 8x10 enlarger using 240mm process lens) counteract the in camera vignetting of an image taken minus CF?

no

[Bob Salomon]

I have just been reading this post (well the first half anyway) having just bought a tecno 6x17 with fixed lens. It came with a center filter IV which i presume mates well with the 90mm SA. The optical details in this post make sense to me, but if that's the case, where do I get a gargantuan 105mm R72 filter to shoot IR with??
The 77mm Hoya I have been using with my 65mm Grandagon mounted on 6x12 that is for sale, post Linhof just got obsolete... (breath)

105mm is a common size for Heliopan