STC recently announced the release of a revision of their well known Hybrid CPL (Circular Polarising) Filter.

What is the difference between the ‘New’ Pure CPL Hybrid filter and its predecessor? According to STC the new filter has a more neutral colour balance.

I have used the original STC Hybrid CPL filter for some years now, so was interested to see the difference between the two filters for myself. As a result I obtained a STC Pure Hybrid CPL filter and put it to the test.

What makes the STC Pure Hybrid CPL filter special?

Made with Schott B270 super tough glass, has a double sided anti reflection, antistatic, oil and waterproof coating, the filter edge is black rimmed to reduce reflection from the edges of the filter, the filter rings are Teflon coated to ensure smooth rotation in addition to this a special polarising film is used . All in all this makes for an ultra light and ultra slim polarising filter which also cuts UV light.

Being a Hybrid filter it cuts light transmission by only 1/2 a stop whilst giving a 70% polarising effect.

The filter is supplied in a square hard plastic padded case, also included are a high quality lens cleaning cloth, a UV test card (to prove how much UV light the filter blocks) and a certificate of accreditation– STC filters are individually numbered, this identifies the filter when registering to activate the guarantee.

How the filter was tested.

For comparison purposes both the STC Hybrid CPL and STC Pure Hybrid CPL were fitted to a Nikkor 24-85mm f4.5 – f5.6 AFG lens on a Nikon D800 camera body. The combination was mounted on a tripod, using a remote shutter release. Exposures were made in Aperture Priority, using an aperture of f11, metering was set to Matrix, 100 ISO, Neutral saturation and Daylight balance, files were saved as NEF and converted to Jpeg for website use in Adobe Camera Raw without adjustment.

The NEF files were examined at 100% in Photoshop on a colour calibrated monitor.

Making the test images

Exposures were made without filter and at full polarisation. The filter ring was rotated several times on both filters to ensure that the full polarisation effect was used..The Teflon coated filter rings made rotation smooth with just the right amount of resistance.

When using full polarisation underexposing by 1/2 a stop sometimes helps compensate for the darker blue sky causing the camera to overexpose.

All photographs were taken in full sun from between 11.00 and 4.00

Test Images

                                                                                                                       Colour saturation

Without filter                                                 Original Hybrid CPL filter                                       Pure Hybrid CPL filter

 

Notice the difference in the RGB channels in the example screen shots below

                                                                                                                              Without filter

Original Hybrid CPL filter

Pure Hybrid CPL filter

Without filter                                           Original Hybrid CPL filter                                       Pure Hybrid CPL filter

 

                                                                                                                              Polarisation

Without filter                                             Original Hybrid CPL filter                                       Pure Hybrid CPL filter

 

Without polarisation                                                                                                      Polarised with Pure Hybrid CPL Filter

 

Without polarisation                                                                                                      Polarised with Pure Hybrid CPL Filter

 

Colour difference between filters

 Left –  Original Hybrid CPL filter colour balance                                                          Right – Pure Hybrid CPL filter colour balance

 

Results

As can be seen by the above screen shots the colour rendition between ‘Without filter and Pure Hybrid CPL filter’ are quite evenly matched and more neutral, whereas the original Hybrid CPL filter shows a slight cyan cast. Sharpness with or without  either of the two Hybrid CPL filters is unaffected, nor is there any  evidence of fringing thanks to the ultra slim high quality Schott glass and multi coating used. The Pure filter also makes a very good job of blocking UV light – see the examples below for further proof.

 

                                                                                            STC Ultra layer UV filter                 STC Pure Hybrid CPL filter

 

STC Ultra layer UV filter                 STC Pure Hybrid CPL filter

Conclusions

When viewed on screen photographs taken using the Pure Hybrid CPL filter are clearly neutral, combined with only a 1/2 a stop light loss, excellent polarisation properties and being ultra slim profile and light in weight, add to this the fact that the filter is excellent at blocking UV light – this new version of Hybrid CPL filter ticks all the boxes.

I keep a STC Hybrid CPL filter on my camera lens most of the time, the minimal light loss is hardly worth bothering about, plus it has the advantage that I have instant access to a polarising filter should the need arise.

This filter is a premium product so expect to pay around £138 for a 77mm Pure Hybrid CPL filter.

Would I recommend the Pure Hybrid CPL Filter?

Short answer -Yes!  The STC Pure Hybrid CPL filter will be my main filter from now on.

Extra Sample Images

STC Pure Hybrid CPL filter

 

Combination of STC Pure Hybrid CPL filter and STC ND 1000 clip filter

 

Thanks go to STC and their UK distributor InfinityX for supplying the new Pure Hybrid CPL filter for the purposes of this review.

As an extra incentive to purchase a Pure Hybrid CPL filter (or any other STC filter) there is a special 10% discount to be had when you add the discount code: 2023tpfp10off at the checkout through the link below.

https://www.stcoptics.com/discount/2023tpfp10off

The sun has now started to appear on a near daily basis now. That can mean only one thing!

Time to break out the Infra Red filters!

I should start by thanking our good friends William and Ashley at STC Optics for kindly providing the filters used in this review and  Protech Repairs for converting the Fuji X-E1 to a full spectrum pass filter.

In this review I will be testing 4 STC clip filters – 3 Infra Red pass filters consisting of: 590nm, 720nm and 850nm, in addition to this I will be testing a 650nm UV/IR cut filter.

The frames of  STC clip filters are made from black anodised 304 stainless steel which is virtually non magnetic, the glass itself is a mere 0.5mm thick and has a special nano coating to prevent dust from sticking to it.

First the basics – Infra Red pass filters allow the transmission of infra red light at varying wave lengths – the higher the number the less visible light is allowed through. A UV/IR cut filter on the other hand cuts out both UV and Infra red wave lengths – in the case of the STC clip filter, it absorbs UV light from 650nm. When fitted to a full spectrum pass converted camera and set to daylight balance it effectively becomes a regular camera suitable for general photography once more. (I used this particular set up when on holiday this year to reduce the number of cameras carried.)

How to use the clip filters with a Fuji mirrorless camera.

When using infra red filters of any kind the camera must first be adapted for use with infra red filters – this usually involves having the hot filter (this blocks infra red light) removed and replaced with a full spectrum glass. Warning – do not attempt do do this yourself, if something goes wrong you could be left with a very expensive paperweight! Contact a reputable company to undertake the process. – See link at bottom for my personal recommendation.

Installing the filter

When using the clip filters for a Fuji mirrorless system for the first time, be aware that on the reverse side of the filter the two outer edges have a sticky layer, this is revealed by removing the clear cover layer.

Remove the camera lens and place the filter into the throat of the camera, ensuring the lettering on the filter is facing outwards –  most of the STC clip filters will only fit one way up with the exception of the Fuji filter , this will fit upside down, but with lettering outward. Very gently press the outer edges of the filter to ensure the sticky layer make contact, replace the lens.

 

Inserting clip filter                                                                                                          Clip filter in position

 

Before taking a photograph a custom white balance must be made. This is done by first setting the camera to ‘Custom White Balance’, (the exact method of making a custom white balance vary with each camera model, consult your camera manual for further guidance.) Typically a 590nm balance is created using a white sheet of paper, for 720nm and upwards the white balance is done using green foliage as the neutral point.

The setup

For this review I used a full spectrum converted Fuji X-E1 plus a conventional Fuji X-T1 as a bench mark for daylight colour balance. Two lenses were used – the lake images were taken using a Meike 12mm f2.8 manual focus lens, the broken wall images were taken with a Andoer 35mm f1.8 manual focus lens. Custom white balances were made and set prior to taking the photographs, lenses were stopped down to f8, shutter speed set to Auto and sensitivity was 200 ISO. In both sets of tests the camera used was fitted to a tripod. All images were saved as Jpeg fine, large and 3:2 ratio. Focus confirmed prior to exposure. Lighting conditions were bright and sunny. It is worth remembering that Infra red light focuses at a different point to the visible spectrum, so ignore the fact that when focusing the point at which infinity is sharp will not align with the infinity mark on your camera.

 

Test images

The Lake photographs are shown in ACR (Adobe Camera Raw) to illustrate the wavelengths of light each filter passes.

 

590nm pass filter

720nm pass filter

850nm pass filter

Converted Camera set to Daylight balance – No filter

UV/IR Cut Filter – Camera set to Daylight balance

Unconverted Camera set to Daylight balance – No filter

 

Wall and doorway

590nm pass filter

720nm pass filter

850nm pass filter

UV/IR Cut Filter – Camera set to Daylight balance

Unconverted Camera set to Daylight balance – No filter

 

Additional Sample Images

                                   850nm Pass filter – Image converted to Black and White                                                 850nm filter – No Adjustment

 

UV/IR Cut filter in converted camera – Daylight Balance                                             UV/IR Cut filter in converted camera – Daylight Balance

 

Conclusions

All the photographs were opened and examined at 100% in Adobe CC on a colour profiled monitor, no alterations were made, the images are just as they came from the camera. The images were observed to be sharp from edge to edge and free from distortion and fringing.

The photographs taken with display more detail in the shadow areas compared with the full colour images, it is worth noting that there is a colour balance difference between the images taken with the UV/IR Cut filter and the unconverted camera, this could be down to the amount of UV/IR being blocked by the clip filter compared with a lens without a UV filter and also the variance between the sensor arrangement of the two cameras used, in saying that either of the colour images is perfectly acceptable when viewed on its own.

The all important question is. Do the STC clip filters offer value for money? For a Fuji X series APS-C  prices range from £96.99 for a single STC clip filter infra red filter (including case) to £111.99 for the UV IR Cut filter.

Whilst this might appear expensive at first glance, consider the cost of purchasing a filter for each lens you wished to use and in the case of ultra wide angle lenses that have a protruding front element fitting a filter is not possible.

Taking all this into account, the STC clip filter range offer excellent quality and great value for money. I own a number of STC clip and screw-in filters and would not be without them.

STC are unique in the range of clip filters that they offer, fitting cameras from Nikon Z series to Pentax APS-C and most cameras in between.

 

Update : STC Optics are offering readers of this blog a special discount on all their filters. Use the link below and add the discount code: 2023tpfp10off at the checkout.
Filters can be purchased direct from STC Optics

For further information on Infra Red conversions contact Protech Repairs