Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
06-16-2021, 07:17 AM   #1
Pentaxian
bdery's Avatar

Join Date: Mar 2008
Location: Quebec city, Canada
Photos: Gallery
Posts: 8,772
Experimenting with K&F Concept's ND2-ND400 variable ND filter

Iíve had the chance to play with a variable ND filter from K&F Concept recently. This is my report on it. This being me, it takes the form of a kind of short review 😊

There is a small number of brands for filters which dominate the market, and rightly I take care of what I put in front of my lenses. After being impressed by the companyís system of magnetic filters, I felt quite comfortable testing that one.

The filter ships in a very nice leather case with magnetic closure. Itís better than many other cases Iíve seen, and I actually see myself using that one. In particular thanks to the easy way to pull the filter out : just pull on the piece of fabric (which makes a cradle for the filter). While straightening, it pushes the filter up. Easy and simple.




The filter itself is solidly made. I particularly like the adjustment tab, instead of a pin sticking out, itís a kind of double-sided thumb-rest. Easy to move, less likely to catch on things than a pin, and better looking.





The level of friction is a bit higher than Iíd like, but good enough. There are markings on the side between ND2 and ND400. I would have assumed those dots mark steps where the ND ratio doubles (2-4-16-32 etc) but in that case, the ND400 mark must be interpreted as being beyond the last dot, which would be at ND256. Note that it's somewhat rare for a VND to cover such a broad range while still reaching ND2.

In my tests, I have seen no X pattern regardless of the focal length used (between 20mm and 250mm). I stayed within the boundaries of the scale mentioned above.

The filter creates a subtle yellow tint, thatís not unusual with polarizers (but not something I observed with the companyís magnetic filters). It didn't visibly impact normal shooting.

I used a test chart to see if there was any decrease in resolution. Just like with their magnetic filters, I did not see any observable decrease, thatís pretty impressive! And itís probably the biggest compliment that I can make to that less-known brand.

Below are some test images, just for fun. The results are pretty good!








I will say that the filter is somewhat thick, I much prefer using the ultra-slim magnetic filters, but still Iím glad to have access to a variable ND filter for when thatís needed. I might just try to find a way to attach a magnetic adapter to this VND filter for simplicity.

Hereís the product Iím referring to for anyone interested:

Amazon

For me these results are not really a surprise given my experience with the magnetic filters, and itís an easy recommendation. Cheaper than most alternatives and, it appears, just as good.

06-16-2021, 08:19 AM   #2
Loyal Site Supporter
Loyal Site Supporter




Join Date: May 2007
Location: Flagstaff, Arizona
Posts: 1,120
QuoteOriginally posted by bdery Quote
Note that it's somewhat rare for a VND to cover such a broad range while still reaching ND2.
I presume the mode of operation is crossed polarizers. A single polarizer gives a one stop reduction in light - i.e. it cuts out one polarization, which is half the light. If the two polarizers are lined up, the second one doesn't affect things much - it just passes the already polarized light on through, so 2x sounds about right as a starting point.
06-16-2021, 08:52 AM   #3
Pentaxian




Join Date: Jan 2018
Location: Jersey C.I.
Photos: Albums
Posts: 1,553
QuoteOriginally posted by bdery Quote
In my tests, I have seen no X pattern regardless of the focal length used (between 20mm and 250mm). I stayed within the boundaries of the scale mentioned above.
I've done some testing myself using a couple of "generic" polarising filters Ö (easier said than done unless you fix one so's it doesn't rotate!) Ö I found two factors relevant to the "X" effect.

To not have any problems :-
i) - one filter must be a circular polariser and one must be an "old-fashioned" linear polariser
ii) - the circular polariser must be fitted to the lens first

Having only a very limited range of filters to play with, I was only able to check a couple of lenses with all combinations and the above configuration was the only one that was totally reliable.

Inevitably - YMMV
06-16-2021, 09:00 AM   #4
Pentaxian
Kozlok's Avatar

Join Date: Jun 2012
Location: Albuquerque
Photos: Gallery
Posts: 3,099
Does the adjustment tab work in the little removable door found on most Pentax hoods?

06-16-2021, 11:53 AM   #5
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 21,507
QuoteOriginally posted by Kozlok Quote
Does the adjustment tab work in the little removable door found on most Pentax hoods?
If it does Iíd think it would limit the adjustment range a lot.

---------- Post added 06-16-21 at 02:57 PM ----------

QuoteOriginally posted by bdery Quote
Iíve had the chance to play with a variable ND filter from K&F Concept recently. This is my report on it. This being me, it takes the form of a kind of short review 😊

The filter itself is solidly made. I particularly like the adjustment tab, instead of a pin sticking out, itís a kind of double-sided thumb-rest. Easy to move, less likely to catch on things than a pin, and better looking.

I used a test chart to see if there was any decrease in resolution. Just like with their magnetic filters, I did not see any observable decrease, thatís pretty impressive! And itís probably the biggest compliment that I can make to that less-known brand.
Iím hoping that tab can be removed for hood use. But your description of the friction required to be overcome makes me wonder if this can be used effectively without that tab.
06-16-2021, 12:39 PM   #6
Site Supporter
Site Supporter




Join Date: Jun 2008
Location: Idaho
Photos: Gallery
Posts: 1,614
Now I know two new words - Janpanese and Putter.

Good price for this type of filter and an interesting design with good promotional features. I would consider giving one a try in order to tame those cases where shutter speed or aperture are not the solutions (and there are such cases).
06-16-2021, 04:13 PM   #7
Loyal Site Supporter
Loyal Site Supporter
Paul the Sunman's Avatar

Join Date: Aug 2011
Location: Melbourne
Photos: Gallery
Posts: 3,931
QuoteOriginally posted by UncleVanya Quote
I’m hoping that tab can be removed for hood use.
Agreed!

I see they make several other VND filters: 2-32; 8-132; 8-2000. And a "K&F XB41 77mm Variable ND&CPL Filter 2 in 1 Function Nano Coating No “X” cross".


Last edited by Paul the Sunman; 06-16-2021 at 04:19 PM.
06-17-2021, 05:31 AM   #8
Pentaxian
bdery's Avatar

Join Date: Mar 2008
Location: Quebec city, Canada
Photos: Gallery
Posts: 8,772
Original Poster
QuoteOriginally posted by AstroDave Quote
I presume the mode of operation is crossed polarizers. A single polarizer gives a one stop reduction in light - i.e. it cuts out one polarization, which is half the light.
Correct, that amounts to ND2.

QuoteOriginally posted by AstroDave Quote
If the two polarizers are lined up, the second one doesn't affect things much - it just passes the already polarized light on through, so 2x sounds about right as a starting point.
Correct also. If the two polarizers are aligned, the second one does nothing more.

QuoteOriginally posted by kypfer Quote
To not have any problems :-
i) - one filter must be a circular polariser and one must be an "old-fashioned" linear polariser
ii) - the circular polariser must be fitted to the lens first
A circular polarizer is, in fact, a linear polarizer coupled with a second component which splits back again the light into two polarizations. So indeed it needs to be the second one otherwise the second polarizer won't do anything.

QuoteOriginally posted by Kozlok Quote
Does the adjustment tab work in the little removable door found on most Pentax hoods?
I doubt it. It's relatively narrow but in most cases I don't think it would work.

QuoteOriginally posted by UncleVanya Quote
I’m hoping that tab can be removed for hood use. But your description of the friction required to be overcome makes me wonder if this can be used effectively without that tab.
It's held by two screws.

QuoteOriginally posted by Bob 256 Quote
Now I know two new words - Janpanese and Putter.
Yep, I learn that too :P

QuoteOriginally posted by Bob 256 Quote
I would consider giving one a try in order to tame those cases where shutter speed or aperture are not the solutions (and there are such cases).
Indeed there are many such cases. For videographers of course, but also to fine-tune your aperture and exposure when light conditions vary.

QuoteOriginally posted by Paul the Sunman Quote
I see they make several other VND filters: 2-32; 8-132; 8-2000. And a "K&F XB41 77mm Variable ND&CPL Filter 2 in 1 Function Nano Coating No “X” cross".
Yep that company offers many products. I believe the one I mention is their newest.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
adjustment, decrease, filter, filters, k-mount, mark, nd2, nd400, pentax lens, pin, results, slr lens, tab, test, tripod
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: 58mm Filters: B+W ND1000, B+W CPL, K&F Slim Variable ND2-ND400 sojournaut Sold Items 1 10-07-2018 01:19 PM
Variable ND Filter - Fader ND mark II yusuf Pentax SLR Lens Discussion 2 11-16-2010 11:39 AM
Promaster 72mm ND2 Filter as good as a Hoya HMC ND2? shaolin95 General Talk 1 04-19-2008 03:23 PM



All times are GMT -7. The time now is 05:55 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top