How do rear gelatin filters compare to front-mounted filters, and how should they be handled?
Asked 6/25/2013
4 views
2 answers
0
Some lenses include a rear filter holder, which can be useful when front filters are awkward or impossible to mount, especially on certain ultra-wide or fisheye lenses. How do rear gelatin filters compare optically with standard front-mounted filters? Are there practical advantages such as reduced vignetting, and what are the trade-offs? Also, what is the best way to find, handle, cut, store, and clean rear gelatin filters like Kodak Wratten ND filters?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
2
B&H sells the Wratten 2 filters ND #96 3 and ND #96 4 in 75mm X 75mm squares. They carry the other sizes listed on the Kodak chart as well. Since searching the B&H site doesn't always find them easily, I searched for them by googling "kodak xxxxxxx" where xxxxxxx is the number listed on the Kodak chart. You can also order them directly from Kodak using the Kodak Motion Picture Products Price Catalog.
Since B&H lists microfiber cleaning cloths as an accessory, I would assume they are adequate for cleaning the Wratten 2 filters. Before using a microfiber cloth, I would first try to use an air blower to dislodge any dust. I would recommend you handle them as little as possible and avoid touching them with your bare fingers so that you don't get skin oil/fingerprints on them. Tweezers or non-powdered latex gloves are two ways you could accomplish this. As to trimming, something like an x-acto knife should do the job cleanly and effectively.
From a comment by Stan:
Most all sources recommend sandwiching a gelatine filter between a couple of sheets of lens tissue and using a pair of scissors to trim to size/shape. A soft lens brush can be used to dislodge some dust that a "squeeze-bulb dust blower" leaves behind. Gelatine filters cannot be cleaned, per se. I have never tried microfibre cleaning cloths for delicate optics such as first-surface mirrors and gelatine filters; but, would not recommend them.
Originally by user15871. Source · Licensed CC BY-SA 4.0
user15871
13y ago
0
Generated from our catalog & community — verify before relying on it.
Rear gelatin filters can be a practical option, especially on lenses that cannot take normal front filters. Based on the community responses, rear placement can reduce mechanical issues like vignetting, and some users consider internal or rear placement optically preferable to front placement. That said, compatibility depends on lens design: some wide-angle lenses protrude too far at the rear to safely use a filter there.
The main downside is durability. Traditional gelatin filters are very fragile, soft, and absorbent, so they scratch easily, are hard to clean, and can fade over time. Handle them as little as possible, avoid touching them with bare fingers, store them in their original packaging, and replace them when they age or fade. For cleaning, start with an air blower to remove dust; if needed, a microfiber cloth may be used very gently, but aggressive cleaning can damage the filter.
For buying, the answers specifically mention B&H carrying Kodak Wratten 2 ND #96 filters in square sheets, and Kodak as a direct source. Search by the Kodak product number if a retailer’s site search is poor.
Cut filters carefully to fit the holder, using a clean template and minimizing handling.
Recommended products
UniqueBot
AI13y ago
Your Answer
Related Questions
When should you use a rear gelatin filter instead of a front screw-in filter?
Glass vs gel ND filters: does placement affect image quality?
What changes optically when a filter is placed behind a lens instead of in front?
Can I use a screw-in variable ND together with graduated ND filters in a holder?
Why are most lens filters mounted on the front instead of the rear?