UV Filter Test: K&F Concept vs B+W
Originally posted on Instagram. Notes from the repair bench, kept here as a searchable archive. View the original on Instagram
This is a tale of two filters. Both are UV filters and one is inexpensive and the other a much more costly choice. Which one will be the higher quality filter?
Often clients send me a UV filter installed on their lens when shipping me a repair. If this is the case, I inspect the filter as part of the evaluation process. If the filter does not test well, I send a note with the returned lens stating the amount of error.
I recently received an RB67 lens with a 77mm K&F Concept UV filter attached and of course I checked the filter on the auto-collimator. I really did not expect a really flat surface on this filter as I had not heard of this brand before and many of the large filters are generally not perfectly plane parallel. I was surprised when the target in the finder was sharp and no secondary image so this indicates parallel surfaces. I then ordered a K&F UV Nano K series filter in 58mm size which is the common Mamiya 7 lens size filter. This is because I am constantly asked about what UV filter would be best.
The 58mm K&F filter (less than $20) I received tested perfectly as seen in photo two. While the much more costly B+W filters generally test very good, the B+W filter shown in photo three was not that stellar as photo four shows. In fact, the surfaces were around 12 minutes out of parallel!
Testing was done on a NatCam (Pearl) C-6810 Auto Collimator by putting the filters on a plane mirror and observing the reflected image
What you don’t get on the K&F filter is a brass mount like on the B+W. So, is the brass mount worth $50 or more extra? Keep in mind that I only tested two filters of this line but both results were really good. These were the less expensive Nano K series and the company has a confusing (to me) lineup of various styles.
I have no connection or affiliation with K&F filters and just putting this out there for info. And, in fact I think the best filter is actually no filter at all. While I don’t use or recommend a UV filter, I realize that many people do want one for protection of the lens.
