Which fixed ND filter for the FS100 kit lens?

[Piotr Wozniacki]

OK, so even though I do have a proper set of 4x4" ND filters for use with the matte box, and the Heliopan vario ND - I decided that for the kit lens I also need an old good screw-on fixed ND one, too...

The reasons are two-fold:

- the kit SEL18210 lens is the one I most often use in R&G style of shooting, so I'd like to put something on it that cuts a good amount of light, and forget about it - no adjustments

- of all my glass, it's the kit lens that is most prone to exhibit the dreaded cross-hatch vignette with the variable ND filter

However, I'm uncertain on which ND value filter I should buy. On a bright sunny day at this time of year, keeping the shutter at 180 deg, I need to close the kit lens as much as F22 to get proper exposure... I realize a single ND filter will not cover all lighting conditions / DOF requirements, but if I define aperture in the 4.0-8.0 range as my goal - which ND value do I need?

My calculations suggest at least ND 1.5, but I don't have much experience with external filters as all my previous cameras had internal ones. Can someone more knowledgeable suggest the best compromise?

Of course, if I really need a shallow DOF, I will not hesitate to increase my shutter speed from 180 to 90 deg, which will give me some extra flexibility..

[Cees van Kempen]

Hi Piotr,

It seems you have the Heliopan. You could put the Heliopan on your lens on a day with 'standard' light conditions (I realise this doesn't exist as such, but I mean on conditions that you take as your reference) Turn the Heliopan in a setting that gives you the filter setting you like most and see what fixed filter will correspond. I believe the Heliopan has markings, that indicate the filter level.

Cees

[Piotr Wozniacki]

Thanks Ces for your suggestion - I have already decided to go with ND 1.2. Four stops cut will bring me down from F22 to F5.6 on a sunny, summer day - which is in the middle of the kit lens' maximum aperture range. Should I need to close even further (like for those special, extremely shallow DOF scenes in full sunlight), I can always use shutter speed of 1/100th. Otherwise, I'll be fine with smaller apertures like F8.0.

Of course on a cloudy day the ND 1.2 might be a bit too strong, but I can always use my 77mm variable ND Heliopan with a step-up ring from 67mm. For indoors shooting, the kit lens doesn't need ND, anyway.

Piotr

PS As a second thought, I guess getting 2 filters (like 0.9 and 0.6) would cover all lighting conditions, but I'm reluctant about stacking screw-on filters - given the FS100 reflections vulnerability... What do you think? Does anyone stack 2 screw-on filters on the stock lens?

[Matt Davis]

I used to - so long as you use the petal lens hood (or some sort of lens hood) you should be fine unless the light is going staight into the lens. After all, this is what's happening in your matte box most of the time. Same rules apply.

[Piotr Wozniacki]

Matt,

True about the mattebox... But there also is another reservation:

- in order to be able to keep using the petal hood, I'd like to go with 67mm version of the filters for my kit lens. Won't they be vignetting when stacked? Any experience with this?

Even my 77mm Heliopn slightly vignettes at 18mm (and I'm not talking about the dreaded cross hatch vignette!)
TIA,

Piotr

[Matt Davis]

Ah yes, very wide lenses. Different story - hence matte boxes.

Before we go all 15mm, there are non-petal lens hoods referred to in other threads that have the 3 stage rubber hood. I know these to work in at least two of their three stages.

However, Genus matte box with Pola and ND grad works with Genus pushed all the way back, and I have to admit that as soon as it looks like I need Pola and ND together, much as I hate it, it's matte box time.

My lenses tend to wear either a Vari-ND *OR* an ND/Pola if I'm shooting FS100 in DSLR mode. I don't tend to stack even if it's theoretically possible. I remember trying to do this on a building site with 30 mins to do a full set of GVs (and it was a BIG site) and thought 'there has to be an easier way' and bought a matte box.*

And in fact about to invest large sum of money with Dear Sam Morgan Moore for a rig that accepts this issue and lets us move forward. Sigh. I feel for you with the drop-arms debate on your rig post too.



* Okay, so it was with an EX1, but the theory still applies. It wasn't the vignetting, but the buggeration factor at that point.

[Piotr Wozniacki]

Wait a minute, Matt...Are you saying you can use the 77mm 3-stage rubber hood (with 67->77 step-up ring) on your SEL18-210 lens, and it does NOT vignette at 18?

Mine does :(

[Matt Davis]

No, not saying quite that. We're into 'FOAF' territory here, and the bigger 'medium format' rubber hoods were being discussed. Similar to the Lee system stuff. Hence there comes a point at which one realises why Matte Boxes were invented (lens shade sits back a bit, filters are really big and don't vignette on wider lenses).

Basically, Kit Lens style >18mm, I think you're okay with a couple of filters, 11-16 - "get thee a matte box". As far as rubber lens shades, the medium format ones are okay for 'sort of' 11-16 if you find a big enough one, but the 'poke out' value of the stacked filters is also a limitation.

[Piotr Wozniacki]

OK thanks - now I'm clear :)

Piotr

[Piotr Wozniacki]

Trying to make up my mind on which fixed ND filter to buy for the kit lens, for R&G shooting and considering the vario-ND Heliopan doesn't fit the hood, and the 77mm rubber hoods vignette - I realized there is one more important factor to be considered:

- at which aperture value do diffraction softness start on the kit lens?

I don't have access to resolution charts etc., so I can only judge with my naked eyes - and must say haven't noticed any at up to, and including, F11... But perhaps some of you guys have more precise data to share?

TIA,

Piotr

PS. BTW, the same question applies to the 11mm pancake with the 0.75% wide converter combo, as this is almost impossible to bet NDed at all :(