Using filters on LF lenses

[Alan9940]

For 40+ years now, I've always held thin gel filters against the front of the lens whenever I needed a filter (don't actually use 'em all that often.) I have a need to use a glass filter because my hands will be working a computer. I've seen other photographers using filters on the front of the lens, but is there any considerations or reasons why I couldn't screw one onto the rear element? Assuming, of course, that threads are available. Seems like it would be a good place to have a filter; eliminate reflections, light flare, etc. Would vignetting be an issue? Would the image quality be degraded?

Thank you.

[j.e.simmons]

I’ve used filters behind the lens many times. You may have to refocus.

[Tin Can]

Horseman offered a LF rear lens filter holder

I have one somewhere, never used it

I also have a DIY one for Horseman, it was wood glued to the back of a Horsemen lensboard

None for sale

[Drew Wiley]

Most lenses are not designed for rear filter use. A few are. There can indeed be an image quality penalty. I've tested for that with high quality MC glass filters. Guess it depends on how much you need to enlarge the neg; but I'll never rear-mount one again. A second liability is that you'll be composing and focussing with a dimmer image, whereas during normal front-mount filter applications you can do all that first, and then, afterwards, apply the filter just before the shot. As far as reflections are concerned, you need a good compendium shade regardless, in flare-prone situations.

[Bob Salomon]

Any dirt, dust smudges, etc will effect the lens from behind much more then in front. And there will be a focus shift.

[Alan9940]

Thank you, all. Front it is!

[Mark Sampson]

I've been putting gel filters behind one of my lenses for 25+ years and never noticed a resolution or contrast difference. It's a 1950s Schneider 121/8 Super-Angulon, where ong ago I attached a Calumet "Xenophon" gel filter holder; it fits on the back of the lens board.
Focus shift, well, I put the filter in first. Admittedly not the theoretically perfect answer, but it does work. Since I'm running low on gels, I may have to break down and buy a few 82mm threaded filters.
...and per Ansel Adams, the focus shift with a filter behind the lens is 1/3 the thickness of the filter.

[Oslolens]

Any dirt, dust smudges, etc will effect the lens from behind much more then in front. And there will be a focus shift.
Focus shift and Refocus is mentioned now and then, please confirm my assumption the focus shift is only when attaching filter after focusing without filter first.

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[j.e.simmons]

Oslolens, that is correct. Focus first, add the filter, refocus. Or add the filter and focus for a single time. Some say simple gel filters don’t require refocusing.

I’ll point out that Sinar shutters, which go behind the lens, have cutouts on the rear for filters to be attached.

[Alan9940]

I've been putting gel filters behind one of my lenses for 25+ years and never noticed a resolution or contrast difference.

I, too, have used gel filters behind the lens for 40+ years. But, in this case the filter I need is very specific and can only be obtained as a glass filter. I looked at all the lenses I plan to use and I can get a 72mm filter and use step-up rings for the smaller lenses.

[Bob Salomon]

Focus shift and Refocus is mentioned now and then, please confirm my assumption the focus shift is only when attaching filter after focusing without filter first.

Sent fra min SM-G975F via Tapatalk

Focus shift is focus shift. If you place a filter behind the lens, and that lens was not designed for a rear filter, then you have created a focus shift.

[Mark Sampson]

Bob, of course you're right. But sometimes, "the perfect is the enemy of the good".

[Bernice Loui]

Sinar shutter has a 103mm glass or gel filter holder built in. Some LF lenses have a threaded rear element specifically designed for a threaded on filter. Some small imager/roll film lenses like the Canon 14mm f2.8 has a gel filter holder on the rear lens mount.

Rear of the lens filter works. The focus shift incurred MUST be compensated for by checking focus with the filter in place on the lens rear.


Bernice

[Drew Wiley]

Gel filters are just so damn susceptible to hazing, embedded grit, and fingerprints, that I only use them in the lab (never in the field), and only when I need a particular flavor which simply isn't available in high quality glass.

Mark - here we go again with the old mythology - "as per Ansel Adams", as if his opinion was definitive. Put that in context, way back when he said it. Ever seen some of his prints from sheet film negs enlarged more than 3X ? - they're anything but sharp, often a mess, really. I'm personally more interested in how to do things today, with far more optimal films, lenses, cameras, and yes, way better multicoated filters too. Not everyone is after a "retro" look.

[Bernice Loui]

Gel filters do not like getting wet... They are very fragile and easy to damage. Good high quality dye in mass glass filters hold up good for all the correct reasons.


Bernice



Gel filters are just so damn susceptible to hazing, embedded grit, and fingerprints, that I only use them in the lab (never in the field), and only when I need a particular flavor which simply isn't available in high quality glass.

[Drew Wiley]

Gels also widely differ in how the fade and age. The official Wratten handbook gives the relevant specifications for every one of them. And there is always a risk when buying old bargain ones, even in unopened sleeves, that they might be be partially faded. On a positive note, having all those specifications available, including the actual spectral transmission charts, makes Wratten gels very valuable for those kinds of technical applications many of them were designed for to begin with. But it's a big mistake thinking one is going to save money going gels over coated glass; many of them are quite expensive. I have quite a set of specialized gels, but pamper them; some of these are no longer available.

[Bob Salomon]

Gels also widely differ in how the fade and age. The official Wratten handbook gives the relevant specifications for every one of them. And there is always a risk when buying old bargain ones, even in unopened sleeves, that they might be be partially faded. On a positive note, having all those specifications available, including the actual spectral transmission charts, makes Wratten gels very valuable for those kinds of technical applications many of them were designed for to begin with. But it's a big mistake thinking one is going to save money going gels over coated glass; many of them are quite expensive. I have quite a set of specialized gels, but pamper them; some of these are no longer available.

In 1986 we became the USA distributor for B+W filters. First thing that happened is that Helix asked us to take back drawers full of special order B+W custom made Wratten filters that they had ordered years earlier from Bogen. While they originally thought that this was a great idea they found that Wratten gels, sandwiched between glass, also faded over time and with exposure to light and temp.
Helix eventually threw out whatever they had.

[Bernice Loui]

Think Tiffen also did this with similar results.
Gel filters simply do not last, they are essentially disposable filters. IMO, if one wants to have durable, reliable-predictable filters, get high quality glass filters. They are worth the $ in the long run. Have a good number of B+W filters that are decades old, they have held up good. Their brass rings are a plus even if the weight is more.

Gel filter sandwiched in glass Bad idea,
Bernice


In 1986 we became the USA distributor for B+W filters. First thing that happened is that Helix asked us to take back drawers full of special order B+W custom made Wratten filters that they had ordered years earlier from Bogen. While they originally thought that this was a great idea they found that Wratten gels, sandwiched between glass, also faded over time and with exposure to light and temp.
Helix eventually threw out whatever they had.

[Bob Salomon]

Think Tiffen also did this with similar results.
Gel filters simply do not last, they are essentially disposable filters. IMO, if one wants to have durable, reliable-predictable filters, get high quality glass filters. They are worth the $ in the long run. Have a good number of B+W filters that are decades old, they have held up good. Their brass rings are a plus even if the weight is more.

Gel filter sandwiched in glass Bad idea,
Bernice

When we dropped B+W to become the Heliopan distributor they also refused to do sandwiches.

[Drew Wiley]

Tiffen has a special thermal film sandwich process involving their own materials, not Wratten gels. I'm glad they've been around for a long time because in terms of glass filters per se, they have the biggest selection available. Only quite recently, and with just a few items, has coating become an available option. It helps, but don't expect it to be in the same league as Heliopan or B&W or Hoya.

The ordinary uncoated Tiffen filters attract smudge and condensation quite easily, and have to be constantly cleaned. And the sandwich-style construction does affect sharpness a tiny bit, relatively negligible in large format applications, but potentially a practical factor in enlargements from smaller formats. There's also obviously a greater risk of flare with uncoated filters; but that's what shades are for.

Consistency? - I dunno; I don't buy replacement Tiffens often enough. But I do know a 47 blue I bought recently certainly isn't as dense and deep a blue as a 47 I bought from them several decades back (and I'm not confusing these with 47B, which I also have). Reverse fading??? The Fountain of Youth??? I'd like to get ahold of that patent.

[Bernice Loui]

Another filter option for those using APO process lenses in barrel. Take advantage of the filter slot built into the majority of these APO process lenses. It does mean using a filter holder with cut to size disposable Gel filters. Non-round aperture shaped can also be used in this filter slot.


Bernice