Full disclosure - I received this filter via the Amazon Vine review program. Neither Amazon nor K&F has a say over my review.

I am not a professional photographer, but I have been an enthusiast for many years - starting with 35mm film. I do enjoy using physical filters in my photography (more on that below) and so I was keen to try this K&F Black Mist/CPL combo filter. I ordered the 82mm version particularly to try out on my Sigma 35mm 1.2 Art - a lens I thought may be fun with a filter like this in certain circumstances - especially environmental portraiture.

The K&F Concept NANO-X Series Black Diffusion and CPL filter is a premium filter intended to provide a mild 'dreamy' look to images and video, by blooming highlights while still providing good black levels. Those into video production might be more familiar with this. I am primarily a stills shooter, and this is the first time I've laid hands on such a filter.

My impression of K&F in the past has been of a budget low-end brand, somewhere around the level of Neewer - maybe a little better. It's obvious now that they're punching up and releasing ever higher-quality products. This particular filter sits up in the premium range, employing Japanese optical glass and advanced coatings to produce a compelling product. The likes of B+W should not sit on their laurels, less they become irrelevant in the face of such competition.

My thoughts on this filter:

- I took comparison shots on a brightly lit day hoping to introduce some 'bloom' to see what it's all about. For this I took shots with no filter, some with the K&F diffusion/CPL Filter, and some with a reasonably well performing Sirui CPL filter.

- The diffusion effect on the K&F is there, but very mild - this is what I expect from a 1/8 diffusion filter though. I expect this might be better in night photography or stronger lighting conditions. Comparing with the cheaper Sirui CPL, which was a little smeary at the time (cheap diffusion effect), there honestly wasn't a great deal of difference at a glance. The K&F did offer a benefit in achieving that highlight effect while keeping the darks fairly contrasty though - slightly more clarity overall. I need to experiment with this more and look forward to doing so.

- Polarisation is mild, but nice and smooth. It was about on par with the Sirui as far as I could tell.

- Colour balance - while I didn't use a chart, just examining the raw shots in my images and comparing vs no filter, the K&F appears to have done an excellent job. It wasn't noticeable different to zero filter based on the RGB channels. The Sirui CPL did add a warm cast, but the K&F seems neutral.

- Build - no complaints here - very nicely constructed and finished. I really do prefer a nice brass B+W ring - that's just me. I have seen people complain about getting this filter on and off the lens - I think this is really something you need to take care with, as filters are incredibly easy to cross-thread regardless of the make (a filter wrench is not a bad idea - back the filter out as soon as you feel it bind). I do think brass rings fair much better here.

- Coatings - these look good with a nice low reflectivity. I did not perform exhaustive testing, but with the sun from above and slightly behind my scene I didn't notice any significant flaring or nasty artefacts.

- Price - well, K&F doesn't seem to be a budget brand now, with this filter coming in at over AUD200 for the 82mm version (to be fair, this is on the large side). Still, there are frequent discounts on K&F and I have to acknowledge that the glass and coatings appear to be high quality and obviously expensive to engineer and manufacture. In comparison to other premium lens filters I think the RRP is reasonable but I would always look to buy these on a discount, which makes them a much more compelling product.

So with modern image processing allowing so much post-processing latitude, why would you buy a filter like this? It could be argued that there is a bit of fiddling to achieve the same ends in post - and perhaps an inability to achieve exactly the same effect. Or, like me, you just like to do things the old fashioned way. It's a valid point though, but in no way detracts from the utility of this excellent filter.

I'd like to try the 1/4 now. Another filter to add to my stack. It's great to see more serious competition in this market!