Strange colour shifts and a loss in clarity when shooting outdoors or in fluorescent light is a problem that many shooters are familiar with. It’s an issue that rears its head with many cameras, but is especially obvious with REDs, Blackmagic and some Sony cameras. Add a regular neutral density (ND) or variable ND filter and the problems can get even worse.
The problem is caused because digital sensors ‘see’ parts of the light spectrum that the human eye can’t. This light is usually from the infrared and ultraviolet parts of the spectrum. As every sun worshipper knows, there is more light from these wavelengths in the daytime. Different cameras react differently but in general this is what turns blacks into brown or gives them a green or purple tint. It can also make skin tones go way off.
The standard way camera makers try to deal with this is with filtration, preventing unwanted frequencies from ever getting to the sensor. A thin filter covers the sensor and blocks certain light frequencies from getting to it. We often refer to these filters as IR cut, or UV/IR filters.
Unfortunately, it turns out that the filters on many popular cinema camera sensors are not that great at blocking the unwanted wavelengths. Some, like ARRI and Canon, seem better than others, notably RED and Blackmagic.
At the BIRTV show in Beijing SLR Magic were showing a filter that is designed to cure all these problems in a very clever way. If it works well then I expect them to be the big ‘must have’ accessory of the year.
The traditional method cinematographers have used when facing these problems is to add front mounted glass filters. There are several expensive filter options from makers like Tiffen, Schneider, TrueND and NiSi that work to greater or lesser degrees. Anyone who has shot seriously with RED or Blackmagic will be familiar with these. RED users often go further and sit special filters behind the lens in front of the sensor to get a better result.
Even with these filters, the results are not always what was expected. According to SLR Magic’s Andrew Chan, the reason is that while these filters do screen out UV and IR, they also affect other parts of the spectrum adversely. They cause gaps in the spectrum where, perversely, too little light passes through at a particular frequency range. These inconsistencies continue to cause colour shifts. He showed us the diagram below to illustrate what is happening to the spectrum.
As you can see, the problems are even worse when you add a variable ND filter. Most variable ND filters cause a strong colour spectrum shift (some are better than others) when you stop them down. This is because a variable ND filter polarises the light coming in and this can result in a lot of IR pollution. The resulting gaps in the light spectrum cause the bad colour shifts in your images.
Enter the SLR Magic Image Enhancer Pro. The new filter attempts to optimise the spectral curve for UV, visible light, and far infrared to improve clarity. Essentially, it is a totally different “recipe” of filter to other UV/IR blocking filters on the market. It changes the relative spectrum values between 200nm and 1200nm, restoring the spectrum to a more natural balance, without the gaps seen in other filters. If the diagram is to be believed it really is a wonder filter that does what no other can.
SLR Magic claim their filter effectively prevents haze from UV, colour shift, and IR contamination issues. When I asked Chan about the filter he told me that “the Image Enhancer Pro will change the spectrum to look natural in complicated lighting situations as well as when ND is used”. He said that “we make a general correction shaping the spectrum to a curve we think is right”, this is done using around 50 different layers or coatings. He believes it “does not make things sharper, but it adds clarity”. This clarity in turn can aid the appearance of sharpness.
From the quick tests our Newsshooter team did at the show, the filter certainly seems to work well. If you look closely you can see the difference it makes to getting rid of IR pollution and colour shifts. I look forward to a more thorough evaluation in the coming weeks.
You can combine the Image Enhancer Pro with a variable ND or regular ND filter for a much better result than before. The design of the filter is quite slim with this in mind. When combined with SLR Magic’s own variable ND filter, Chan told me, it eliminates the warm colour shift usually seen at the end of the range.
Obviously, variable ND filters with a wider front diameter are less prone to vignetting when you stack an Image Enhancer Pro onto the front. SLR Magic’s variable ND filters seem well suited to the task but other high quality ones should also work well.
Some older IR/ND filters on the market are known to distort the image and have uneven effects which restrict their use with wide angle lenses. I remember my old 486 filter for my Sony EX1 doing this back in the day. At longer focal lengths it had a nasty kind of wavy effect on the image and you couldn’t use it wider than about 35mm (full frame equivalent). Chan claims that these things are not a problem with the Image Enhancer Pro thanks to a different production method. There should be no sharpness issues and no focus shift as the filter is front-mounted. Take a look at the picture below to see the difference between a 486 filter (the greener one on the right) and the Image Enhancer Pro.
One thing that Chan was keen to point out is that many ND filters also exhibit a colour shift that is clearly visible. A green, or red, or blue tint that is obvious when you look through the camera. This is not something that the Image Enhancer Pro can fix. The solution here is to combine the Image Enhancer Pro with better quality ND filters which are more neutral.
Also the Image Enhancer Pro is not designed to be used with other front-mounted UV/IR, IR ND and IR Cut filters. It cannot restore gaps in the spectrum made by these filters because it cannot balance out colours that have already been removed.
Initially the Image Enhancer Pro will be available in round filter sizes. A 52mm is expected to cost around $70 US and a 82mm around $100 US – although this pricing is still to be confirmed and there is no firm release date. The company is considering other filter types and sizes for future release.
SLR Magic were also showing some near-final production versions of their two new PL lenses at the show. The APO-HyperPrime 25mm T2.1 and APO-HyperPrime 85mm T2.1 were originally announced at the NAB show earlier in the year, and now join the APO Hyperprime Cine 50mm T2.1. The new lenses now have an 82mm front filter thread so that the Image Enhancer Pro can be used.
Both lenses will be shipping towards the end of August.
This from SLR Magic:
Hong Kong, China (August 24, 2016) – SLR Magic introduces the The SLR Magic Image Enhancer Pro (IE Pro), a unique filter suitable for use in both photography and cinematography to help increase image clarity and restore color shift issues introduced by light contamination beyond the visible spectrum to digital sensors. The filter will be officially introduced during the BIRTV 2016 show in Beijing.
The IE Pro is a unique filter that optimizes the light spectrum from 200nm to 1,200mn to ensure light rays passing through the filter are natural to the human eye. The digital imaging sensors’ greater susceptibility to infrared light contamination leads to colorcasts when shooting subjects at instances where the light source has increased levels of infrared light that is not visible to the human eye.
Traditional UV/IR filters are commonly used to address color shift and infrared contamination. However, hot mirror type UV/IR filters sold as 680nm, 700nm, 715nm, or 750nm rating typically cut out the red spectrum along with infrared spectrum to produce blacker blacks but will create an unnatural skin tone reproduction. At times, traditional UV/IR cut filters produce a green or red color shift when certain lenses wider than 35mm are used. The SLR Magic IE Pro is designed to work with lenses from wide angle to telephoto.
The SLR Magic IE Pro is designed for use on digital cameras for both photography and cinematography. The light spectrum curve with IE Pro shows the optimization of light transmission through unique attenuation of light in the light spectrum leading to improved clarity within the image and more tonal depth. IE Pro can be positioned in front of your lenses with or without electronic ND filter or in front of your ND filter or variable ND filters. 50-layers of multi-coating is used in the IE Pro to minimize reflections and flare, thus achieving a unique level of optimization across the entire light spectrum as well as attenuate UV and Infrared light to minimize chances of colorcasts and ensure cleaner blacks and truer skin tones.