29 December 2009: Note – the entry below describes a ND400 filter that I received in October 2009. Since then, I ordered another, which was faulty and produced a distinct magenta cross patter (see the comments below). The pattern it produces suggests that the filter is based on two ‘crossed’ sheets of polarising material. Citiwide are currently not able to provide a filter of the same quality as the first one I received, so have refunded me. I am hoping that they will be able to resolve the quality issues as I would be willing to purchase another one, if it works as described for the first copy I received. If I hear that the quality issues is resolved, I will update this page.
I have a B&W ND110 filter already. For those of you who do not know it, it is a very dark filter that allows slow shutter speeds in daylight. You might ask why. Slow shutter speeds will make moving objects blur or disappear in the final image, very handy for atmospheric clouds, waterfalls or getting rid of tourists. The B&W filter reduces light by 1000x or 10 stops, so instead of an exposure of say 1/60, with the filter the exposure is 8 seconds.
The only downside is that the B&W filter is expensive – £35 just for the 58mm version. At some point I want a 77mm version. Also, after successfully cutting down a piece of IR filter for attaching behind the Pentax 10-17 fisheye, I would like to repeat with a strong ND filter. So where do you go for cheap filters? eBay and China or Hong Kong of course! I found a generic Citiwide 77mm ND400 (9 stop reduction) for less than £13 on eBay. At that price I was willing to take a punt. This one was actually purchased as a gift, my intention was to buy a smaller version and get it cut to fit on the back of the fisheye.
Despite the post strike it arrived in the UK from HK in under a fortnight. Initial impressions are good, it is mounted in a slim (3mm) metal mount and seems fine. So how does it compare?
All photos are shot in RAW with the Pentax K100D, 18-55 AL II kit lens at ISO 200. This is the shot with no filter. Camera set to Daylight white balance, f16 1/180second. Click on any of the images to see a larger version.
Below, the real B&W ND110 with Daylight white balance setting. 15 seconds at f16 (approx 11 stops slower).
Again, the B&W ND110 with camera white balance set through the filter. Same exposure as above.
The image below is the cheap ND400 with Daylight white balance (to show the effect on colour this filter has). 30 seconds at f9.5. This filter is supposed to be 9 stop reduction, so one stop ‘faster’ than the B&W, but in practice this is closer to 12-13 stops and was still a bit underexposed.
Again, the eBay ND400, with white balance set through the camera. Not looking too good straight out of the camera. This was another stop slower, 30 seconds at f8 and still a stop or two underexposed.
All is not lost though, despite the obvious colour cast of the filter, it does adjust fairly successfully. This has had a quick tweak for levels in Lightroom. The white balance was set against the white clouds and the vignetting has been adjusted.
Conclusions: There is obviously potential in this cheap filter and I will be buying myself one. For £13 a 77mm 9 stop ND filter is a bargain, the B&W equivalent is £80 and up. But it is not the sort of filter for the impatient. For best results you are going to have to pay close attention to the exposure. Just dialling in 10 stops of compensation does not work and you will have to adjust levels, tone curves etc. Also, depending on how sensitive your camera is to red (and infrared) you may end up getting very odd results that need colour correction, so shooting RAW is essential as JPEGs are not likely to allow enough adjustment without colour clipping. For those of you who like the effect and have the cash to splash – buy the B&W.