Has anyone tried adding a filter holder to lens adapters?

petrochemist wrote:

E Dinkla wrote:

ProfHankD wrote:

Honestly, I haven't found filters all that useful with digital cameras except for special purposes. I suppose a polarizer might be worthwhile... but if the adapter is designed to have a filter with a specific optical thickness, you'd need one even for clear to keep the same rear focus distance, which would still degrade IQ a bit.

I do not see much use for them either but an ND and a polarizer is in the bag. The 58mm step up filter ring added to my 3D printer hoods is convenient for the 58mm caps and the use of the two 58mm filters that I have. Sure there is a risk that dirt on the filter shows faster when more extended from the front element but the depth of the hood for my lenses usually goes along with the focal length of the lens. I am measuring the hood depth all around more precisely now in manufacturing.

https://www.dpreview.com/forums/post/62095208

For the 75mm 5.6 scanner lens mounted into an M42 macro extension tube I made a hood that fits in the M42 thread at one side and a 58mm filter thread at the other side. A deeper hood I made for the 100mm scanner lens also mounted in an M42 macro extension tube. The M42 extension tube mounting makes it all quite universal when both side M42 threads, male/female, can be used. For example in reversing the lens. The diameter of the lens barrel has to be small though. M52 extenders could be used for larger diameters.

100mm on longer helicoid and its hood showing the rear side with the male M42 thread

100mm reversed mounted to the helicoid with a dual male M42 extender

Even projector lenses could be used in M42 female threads when an M42 thread on their barrels is made with a lathe. Studying that possibility; the standard 42 to 42.3 mm diameter lends itself quite good for that work, little to cut off for the thread and enough wall remains. For hoods a female M42 ring at the rear of the hood could be used.

Met vriendelijke groet, Ernst
No photographer's gear list is complete without the printer mentioned !

I use a long m42-52mm helicoid for most of my projector lenses - it's much easier to stick a 52mm stepping ring to the outside of the lens body than cut a M42 thread. Only one of my projectors is too big for this & that's got a very long registration, so might be better connected via a lined drainpipe!

I've never tried reverse mounting my projectors, perhaps I should just stick filter rings to the front as well - not quite as neat as your adaptions admittedly.

Adding a very short M42 extension tube with the filter glued in behind helicoid and lens could be a solution for you. There are also the M42 to M39 adapter rings of about 4.5 mm thick that may fit somewhere between a male and female M42 connection. Filter glass disc of 38mm diam should fit with some glue into the 39mm female thread. Odd imperial pitch so unlikely a filter would fit that thread right away.

Aliexpress.com see M39-M42 Camera Lens Adapter Ring M39 Lens M42 Romp Ring M39-M42

For RF wide angle lenses that did not cope well with the FF sensors there has been some R&D done at the Fred Miranda forums. Most solutions had one extra element (dioptr filter) implanted at the front but I recall one at the rear of a lens too. So extra glass at the rear is not always becoming an issue.

I try to avoid huge lens constructions. Is the 52mm helicoid not much wider than the M42 one?  I understand the 52mm helicoid has a thread of 0.75mm pitch which is like filters can have so a stepping down ring from 52 to ? could do it.  What is the best size then at the 42<>42.3mm diam of slide projection lenses?

Reverse mounting of projector lenses is not delivering much I guess. Wide aperture is an advantage but the designs aimed at scaling beyond 1:10 and most have focal lengths that start above 60mm, you will need very long extensions to get to that scaling when reversed. Filter step up/down ring with the right diameter to glue on will not be that difficult to find. Male/male 52mm might be available too. I received a 58mm this week.

Met vriendelijke groet, Ernst
No photographer's gear list is complete without the printer mentioned !