Neutral Density Filters

Welcome to the second of our reviews involving STC filters.
In this we are testing something quite different. We are testing an ND filter that actually fits inside the camera, rather than attaching to the camera lens, certainly not something we had seen before and hence were eager to try.
Again we are indebited to William Wu of STC Optics for his continued support.

Why use an ND filter?
There are times when one might wish to use a large aperture, for example to give a shallow depth of field, whilst maintaining optimum shutter speed, lighting conditions are so bright that the camera cannot use any higher shutter speed and is already at smallest aperture, or the reason most photographers use ND filters, to enable them to use extremely slow shutter speeds to obtain blur of moving subjects, for instance moving water.

We have tested the STC IR cut ND64 filter against several conventional ND filters, in this instance the opposition are a NISI ND1000 – a high end competitor, Hoya ND4 – a well known and respected brand, Rocolux ND400 – a readily available on Ebay budget filter and to make things interesting a Zomei ND 2-400 variable ND filter, another filter available through Ebay and Amazon.

Once again we have used a Nikon D800 body, this time fitted with a Sigma 24-60 f2.8 lens, tripod mounted and triggered by a remote release, set to daylight balance, ISO 160 and using an aperture of F10.

Fitting the STC is straightforward, on Nikon bodies: switch camera on, remove lens, switch camera to ‘Live View’,place filter inside camera throat (see photo below), put lens back on, switch camera back to ‘Live View’ (due to camera turning ‘Live View’ off when lens is refitted), then switch camera to manual focus.






Test conditions.
The filters were tested under two separate weather conditions, cloudy and in full sunshine also at two different locations.

Whilst all the filters can cause the camera to under expose by around a third to half a stop, this being due to the considerable reduction in light reaching the metering system, although this does not appear to affect the auto focus system.

Under both sets of lighting conditions, the results were the same.
In reverse order of colour balance and quality the results are as follows: Rocolux at the bottom of the pile! Horrible muddy red colour cast, although sharpness was ok, Nisi, displayed a cyan cast and loss of sharpness, Zomei variable ND at its darkest setting gave a blue cast and again a loss of sharpness, Hoya, although a weaker density still displayed a red bias, but maintained sharpness. The outright winner was the STC drop in filter, it was neutral in colour and maintained sharpness across the frame.

The evidence.








Control image













































Cropped section






Images all brightened to match control image.

Final thoughts

Why is the STC filter so much better? For several very good reasons, firstly, the filter has been coated with an Infra Red blocking layer which removes the excess infra red that reaches the camera sensor when using long exposures, none of the other filters tested here have this technology. Secondly, because it fits inside the camera, only one filter is needed rather one for each different filter thread size on your lenses, economically it makes a whole lot of sense!

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