Note: Refer to the bottom of this post for a further update made several months after writing this review originally.
Filters are essential to my landscape photography. The three filter types that every landscape photographer should have in their arsenal are graduated neutral density (GND) neutral density (ND) and circular polariser (CPL). GND filters need to be the rectangular gel type that fit into a filter holder system for swift changing and height adjustment.
The first filter holder system I ever bought was the Cokin Z-pro system. The holder is very basic and made from cheap plastic but it is reliable and still functions fine today after many years of use. As far as the Cokin filters go, the CPL is excellent, the GND's are okay but the ND filters have an awful magenta colour cast. Because of the colour cast issue I switched to Lee filters which have a great reputation for quality. Lee's glass ND filters are fantastic and any colour cast they have is subtle and virtually imperceptible to my eye. The Lee GND's are gel and are also excellent.
Recently, I had cause to re-view my filter system after buying the fantastic Pentax 15-30 lens.This fast, ultra-wide lens doesn't allow the fitting of a regular 100x150 filter holder system as it has a fixed, petal-style hood and no filter thread. It's field of view is also too wide for the smaller filters. Fortunately, because this lens is manufactured by Tamron and was based on the existing Tamron 15-30 lens, there were already specialized filter systems in the marketplace that would fit both variants of the lens. I looked at a few different options including Lee but the one I settled on (partly because of the reasonable price) was the Benro FH-150 system. Deciding to jump in with both feet I also got the Benro FH-100 with 82mm lens adaptor to replace my old Cokin holder as my primary filter system for my other lenses.
The holder seems to be very well made from high grade aluminium and polycarbonate, with the locking ring and adjustment knobs finished an attractive anodized blue colour. It is quite easy to install and the lens doesn't have to be removed from the camera like some systems. There are four small lugs which locate the adapter using the shape of the lens hood. The locking ring has to be tightened with a fair amount of force to get it tight enough to hold firmly on the lens but once this is done I have never had any fears of it slipping off. (It looks like Benro have redesigned the holder since I bought this which you can see at the manufacturer website. They have replaced the locking ring with two smaller knobs. This design may well provide an easier method of getting firm attachment.) Once the holder is on I find that I can even fit the friction fit lens cap onto the partially protruding hood which is handy.
The two blue knobs on the back of the holder perform two functions. Once loosened slightly the holder will rotate on the adapter to any angle, an important feature for working with GND's. This works very well and the knobs tighten easily and firmly. However, if you loosen the knobs too much you are in danger of the whole assembly coming off as this is the way the holder is dismounted from the adapter. When I first realized this I was concerned about it happening by accident while in the field. In practice though I have not found this as likely as I had thought. Once the knobs are tightened there is little danger of them loosening off enough to allow the holder to slip off and they only require a tiny amount of loosening to be able to rotate the holder. I just make sure they are always tight before I take my hands off the holder.
Rather than buy the Benro filters I decided to stick with what I know and use Lee. I especially like Lee's 6 -stop Little Stopper ND's. Fortunately the Lee filters have the same 2mm thickness as Benro so they suit the filter slots fine. I purchased a 4 stop 150x170 GND and the 150x150 Little Stopper. The GND works exactly how the Benro version would. The Lee Little Stopper has a foam light seal attached to the back of it to suit the Lee holder. This seal matches the Benro holder base and seals perfectly against it when used in the first slot (which would only be used if you weren't using the CPL). The CPL for this holder is a slim 150mm unit that is designed to fit the holder specifically. The holder design allows for the CPL to be rotated even though it is fitted at the back of the holder in the first slot. I have not yet purchased the CPL so can't comment on its use.
The filter slot stack can be disassembled by unscrewing the Allen head screws using the supplied Allen key. The plastic guide for the first slot is either a standard slot or the modified CPL slot if you choose to use one. Only 3 slots at a time can be used.
The large size of the holder system and the filters brings an issue with it - storage and cartage. Fortunately my Gura Gear Kiboko pack is deep enough that I can fit the filters into the main compartment standing on their sides and the holder will readily fit in one of the front pockets. Overall it is definitely a bulky system but the image quality of the Pentax 15-30 is so good that the extra bulk and weight of a filter system is worthwhile.
Though much more compact than the FH-150, this holder has some similarities in construction and style. It is equally well made and has the same method of attaching the holder to the adapter and rotating the adapter (the twin blue knobs). Unlike the FH-150, it of course just attaches directly to the lens filter thread via the adaptor, which is available in a few different filter sizes.
The filter holder slots are quite tight which is good as it prevents accidents but it can be a bit difficult to insert them sometimes. As with the larger 150x150 version, the 100x100 Little Stopper has a foam seal attached to the back of it for preventing light leaks or internal reflections (something I've never had issues with actually). It is possible to fit this filter in the first slot and the foam seals well against the holder base but it is a very tight fit. So tight that in the field I find it easier and safer to just use the second slot and put the GND in the third slot leaving the first empty. I guess the Benro ND's would not have the foam seal attached since the holder itself has a circular foam seal glued to it. I may peel off the built-in seal at some point in time which will doubtless make it easier to get the Little Stopper into the first slot.
The FH-100 has an interesting solution for the CPL. The kit I got came with the 82mm threaded CPL which is a very slim design. It screws onto the front of the two piece lens adaptor while the back of the assembly screws onto the lens. The two parts are free to rotate and the knurled edge of the front part is exposed behind where the holder mounts, so the CPL can still be easily rotated even when the filter slots are filled and the CPL is not accessible otherwise. If you refer to the picture above you can see that when fitted, it is flush with the mounting surface of the first filter slot so is completely protected and light sealed against the ND. The CPL can be used as a standard filter and screwed directly onto the lens if desired. It seems to be of high standard as I have noticed no affect on image quality. I typically leave it in place all the time and just rotate it to turn the effect on or off as desired. A little side benefit of this arrangement is that the lenses standard front cap can be attached to the CPL's front filter thread for protection of the CPL (or the adaptors front thread if the CPL is not fitted).
There are a few options for filter systems when it comes to the regular 100mm filter format. The Benro FH-100 holder is a great solution and a substantial upgrade in quality and CPL integration over my older Cokin holder. I can't say if it's the best system available as I haven't tried them all but it will serve my purposes perfectly so I have no hesitation in recommending it, especially considering its reasonable price and the very effective implementation of the CPL.
The filter holder choices for the Pentax/Tamron 15-30 are more limited. The comparable quality alternatives are Lee, Nisi and Wonderpana, none of which I have personal experience of. I find the Benro FH-150 to be very well priced (certainly cheaper than the Lee system), easy to use in the field, reasonably compact in size and with excellent manufacturing quality. With the flexibility of using either Lee or Benro filters I certainly suggest that any owner's of the Pentax 15-30 give the FH-150 serious consideration.
I have now been using these systems for several months and can report back with some further comments. Generally I am very happy with the FH100 system and do not really have anything more to add to what I said above.
The FH150 system does the job I need but as I discussed previously the bulky and unwieldy shape of this unit and the filters are something of a headache. This fact applies to any 150x150 filter system though. It is a judgement call on whether it is worth it or not but I like the 15-30 lens I am using so much I will continue to put up with the filter system.
Since writing the review I have purchased the 150mm circular polariser for the FH150. In order to fit this into the holder requires disassembling the stack of slots and putting in a special curved guide to the bottom of the stack. This works really well in terms of holding the filter securely (a good thing given the size and fragility of a piece of glass like that), however it is a real nuisance for using it in the field. Fiddling with tiny screws and plastic parts while actually standing on location is far from practical plus the Lee Little Stopper with its attached foam stripping is far too tight a fit and I become limited to the use of only 2 slots (leaving an empty one between the two filters). If you want to use the CPL with both an ND and a GND, I would advise using only the Benro ND filters not Lee. In the end I decided to leave the CPL out of the holder by default and only install it ahead of time if I know I will be going to a location that really calls for it (such as a waterfall for example).