STC Aura UV Filter

Being a long term user and supporter of STC filters, I am always interested when a new STC filter is announced.

However before I get to the review,  I must first extend my thanks to Ashley at STC for very kindly sending me the filter in question for me to test, along with several other equally interesting filters to review.

What is the filter and what makes it special?

It is a new generation UV Protector filter. According to STC’s website the filter is a world first and world thinnest 0.8mm filter glass.

The filter is made from new generation world thinnest chemical-strengthened 0.8mm single-crystal glass. The super slim lens is tough enough to withstand 700MPa, to prove this a 45g golf ball dropped on the filter from a height of 2.5mtrs, the filter was undamaged- impressive! In addition to this the STC Aura filter has lowest the Optical Path Difference in the industry – minimizing diffraction within the glass, thus enhancing edge detail restoration capabilities which is a must when shooting at 120 megapixels and 8k video. The filter is double sided anti smudge and anti-static nano coated. The filter ring itself is a rather fetching gunmetal coloured aluminium and is designed to be shockproof.

The STC Aura filter is supplied in high quality square plastic case fitted with foam inserts, also included in the package is a STC lens cleaning cloth, a UV test card plus a guarantee booklet that is signed by the technician who quality tested the filter. Also worth mentioning is the fact that all STC filters have a serial number on them, which is needed when registering the one year guarantee.

To get an idea of how well the STC filter performs I tested it against 3 other UV protection filters – these were: Hoya Pro 1 Digital UV, Kenko UV and STC Ultra Layer SMRC UV.

Filter Specifications:

Filter                                      Thread size             Coating                Weight

Hoya Pro 1 Digital UV                77mm                 Multi Coated               35g

Kenko UV                                     77mm                      None                       20g

STC Ultra Layer UV                    77mm                 Multi Coated               17g

STC Aura UV                               77mm                 Multi Coated               14g

 

Test Equipment and Proceedure

For test purposes I used a Nikon D800 equipped with Nikkor 50mm f1.8 D, Nikkor 24-85mm f3.5-4.5G ED and Nikkor 80-200mm f2.8 ED mounted on Manfrotto 190 tripod fitted with 115 head. All exposures were made using a remote release cable and the camera eyepiece cover in place.

Camera settings were: Standard colour, Adobe RGB Colour Space, Daylight balance, Contrast Normal, 0 exposure adjustment, ISO 100, Aperture Priority, Matrix Metering. All images were saved as RAW files.

The first 2 frames of each focal length test were made without a filter, then 2 exposures were made with each filter in place. Tests were made at 24mm with 24-85mm lens, 80mm and 200mm with 80-200mm lens.

All the filters were tested for their UV blocking capability using STC UV testing patches in bright sunlight.

Results

The first test performed was the UV blocking test – For this I used STC UV testing patches in bright sunlight.

The Hoya filter allowed a little UV through whilst the Kenko filter blocked very little UV and both STC filters blocked UV fully. The fact that the Kenko filter failed to block practically any UV light is to say the least a little worrying, admittedly the filter is the budget version offered by Kenko but still not an excuse.

 

                            Hoya Pro 1 Digital  UV                      Kenko UV                               STC Ultra Layer UV                         STC Aura UV

The second test involved photographing a gray target in diffused early morning light with each filter in turn – the purpose of this test was to check for any significant colour and density issues with the filters. The camera was equiped with a Nikkor 50mm f1.8 D lens, aperture was set at f8 and exposures were made in aperture priority mode. Subsequently the images taken were viewed in Adobe Camera Raw where the image and histogram of each file was examined for colour shifts.

The colour shift test was performed by overlaying each of the histograms one at a time over the image taken without a filter.

All the filters darkened the blue mid-range very slightly – the Kenko filter additionally darkened the blue highlight range slightly, whilst the STC Ultra layer filter reduced the mid range blue peak slightly and also darkened red mid range by a slight amount, finally the STC Aura filter made a small reduction in the peak of the green mid range.

 

Without filter

Hoya Pro1 Digital UV filter

Kenko UV filter

STC Ultra Layer UV filter

STC Aura UV filter

 

The third and final test was the sharpness test, this envolved making a series of exposures of Eastbourne Pier at 3 different focal lenghts with all four filters, the RAW files for each exposure were viewed at 100% in Adobe Photoshop using a colour balanced monitor – an image without a filter used was the baseline upon which all the filters were judged.

All images were saved as jpeg files in Photoshop without any corrections made.

From left to right images are: Without filter, Hoya Pro1 Digital, Kenko, STC Ultra Layer, STC Aura

Nikkor 24-85mm at 24mm

Nikkor 80-200mm at 80mm

Nikkor 80-200mm at 200mm

Under critical examination the Hoya Pro1 Digital showed a very slight increase in contrast, Kenko filter was a little warmer, the STC Ultra Layer filter displayed a slight increase in contrast and a slight increase in edge sharpness, the STC Aura filter was similar to the STC Ultra Layer filter in contrast whilst giving a slightly better edge sharpness.

Conclusions

None of the filters tested displayed a huge colour shift, which is not unexpected. Formulation of the glass and coatings used to enhance light transmission will always make extremely slight differences, but only close comparison of the histograms reveal this.

Coating of the filters also play an important part in maintaining image sharpness and contrast, however the thickness of the glass also has a part to play in this – thicker glass will diffract light more than thinner glass. This is where the STC Aura filter comes into it’s own, being a world first thinnest single crystal optical glass filter- allied to state of the art coatings. It helps to produce very sharp images with excellent contrast.

Surprisingly when comparing weight between the four UV filters, I was half expecting the Kenko filter to be the heaviest, how wrong I was -it weighed 20g a full 15g less than the Hoya Pro1 Digital. The STC Ultra Layer filter tipped the scales at 17g and the STC Aura filter came in at only 14g.

More worrying was how little UV light Kenko’s budget filter blocked (according to the test- none). To be fair to Kenko, there are other multicoated UV filters in their range which probably make a better job of blocking UV light but for the purposes of this test I wanted to test a recognised budget filter from a known brand (Kenko are part of the Tokina group) rather than one of the  ‘No Name’ brands that are on offer at various outlets.

What you expect from your UV filter and how much you want to spend will certainly dictate which filter you opt for.

If you want an inexpensive piece of glass to put in front of your lens then the Kenko filter is for you, just remember that it does not effectively block UV light. A better but obviously more expensive filter would be the Hoya Pro1 Digital, this filter made a better job of blocking UV light. The ‘Digital’ in it’s description aludes to the fact that the multicoating have been optimised for digital camera sensors. Top marks go to the STC filters, with the Aura filter making it to the top spot due to the better edge sharpness it produced. I tested all the filters with a 36.3mp camera, so imagine the image quality the STC Aura filter will produce at twice and four times that!

Further evidence to how robust the STC Aura filter is can be born out by personal experience – I accidentally dropped my filter onto concrete from at least a metre high, the filter was completely unscathed.

Prices of all four filters are subject to change, but as a rough guide for a 77mm filter : The basic Kenko UV filter costs on average £6.00, whilst a Hoya Pro1 Digital UV filter (now superceeded) or equivelant costs in the region of £73.00, STC Ultra Layer UV filter costs approximately £65.00* and STC Aura UV filter approximately £85.00*

* Prices converted from USD – Please contact UK suppliers for exact prices.

The final question is: What UV filter would I choose? Easy answer – the STC Aura UV filter, in fact I am already using one, it’s top quality!

 

Sample Photographs