When I bought my first expensive lens for my DSLR back in 2011 – it was the Canon EF 70-200mm f/2.8L USM – I felt obliged to protect that precious piece at all cost. Most photographers around the web recommended buying a UV-filter of the highest quality (because “if you buy cheap, you end up buying twice”, they said).
I did some research on UV-filters on film vs digital cameras because I was sceptical.
First off, the UV-filter is quite useful for film, because the UV light, while not visible to the human eye, does expose the film and results in sunny scenery looking washed out. The UV-filter swallows all the UV light (that’s the light with wavelengths below 390 nm) and thus helps to improve contrast and such on your film images.
What about digital cameras?
Well, the UV-filter doesn’t really help here. The simple reason being that the image sensor is covered by a filter already. This filter keeps out both infrared (IR) as well as UV light.
Many photographers will tell you that they use UV-filters to protect their lenses and this might be true. However, while browsing the manufacturers for their various filters, I found that most of them also offer so-called Protector-filters with the sole purpose of protecting the lens front element.
My filter collection
I ended up buying one of these protector filters, the HOYA HD Protector. Later on I also got one for my Fuji X100S (now to be used on my vintage lenses, because most of them accept the same 49mm filters) and I also have one on my crown jewel, the Canon EF 85mm f/1.2L II USM.
Being the most important filter in digital photography and its effect impossible to recreate in post processing, I bought a HOYA HD CPL (circular polarizer) next.
I even got a 10-stop ND-filter in at some point in time (though never used so far *blush*). It’s a Haida Slim Pro II MC ND3.0 1’000x. I bought this filter for 60 bucks on eBay, because a Lee Big Stopper costs around 150 bucks, and that’s without the filter holder. Also, the B+W 10-stop filter costs more than 90 bucks and many reviews found it to not be superior to the Haida filter.
Because I wasn’t sure whether I would ever get serious about landscape photography – turns out that I never did – I only spent like 20 bucks on a chinese copy of the Cokin P system (called TIAN YA) with a 77mm adapter ring and various coloured gradient filters as well as a set of solid ND filters and an ND grad. I will not test the colour gradients, although I got a nice picture using the brown one for a sunrise:
With my recent vintage lens purchases I also got hold of a cheap Hama UV390 UV-filter and a very nice looking Rollei R1.5 Skylight-filter.
Lastly, not so long ago I bought a cheap filter set from K&F Concept on eBay. It’s in 49mm and contains a CPL-filter, a UV-filter, a set of ND’s (2,4 and 8) and a purple filter. The set was less than 15 USD including shipping and it came with a nice carrying pouch and a lens hood, so I didn’t expect too much. But, I wanted the solid ND filters and the polarizer for the vintage lenses.
This image shows most of my filters, with a few specimen missing:
The TIAN YA filter holder for the rectangular slide-filters holds the ND grad. Missing are the 77 and 82mm Hoya HD Protector filters and the Hoya HD CPL.
Let’s start with some tests and comparisons, shall we?
Testing procedure for colour cast and light transmission
I used the Voigtländer Color-Ultron 50mm f/1.8 to compare the 49mm filters and the Samyang 35mm f/1.4 to compare the 77mm filters.
In order to be able to compare exposure and white balance, I used my 5’500K daylight lamp and my grey card as a neutral subject like I did in previous tests. The camera was set to Manual mode at f/5.6, iso 100 and a shutter speed of 0,4″ (the 10-stop filter being the exception, but I’ll explain later). I repeated the measurements several times because some simply didn’t make any sense to me.
Protection, UV, Skylight and that purple thing
What do these filters do?
As I explained before, the Protector does not do anything aside from protecting the front element. With most lenses, it’s also a lot easier to clean a filter instead of the front element.
The UV-filter does filter UV light only, therefore should have no effect on the final image whatsoever.
The Skylight-filter is meant to add some warmth to your photographs while also filtering the UV light. That’s quite handy when you shoot film but not so much with digital images, where you can adjust the white balance accordingly.
The purple filter, called FDL, is a very special case. It’s sole purpose is on film cameras and there it really makes a difference. While everything looks pretty “neutral” to our eyes, no matter what light sources we’re looking at, a film camera is not capable of adjusting the “white balance” like that. Most film was created for the use in natural light, meaning somewhere around 5’500 K. This means that, when you use a film camera in an office with fluorescent lights, your pictures will look green. Using the purple filter will counter that and result in neutral colour temperature and tint.
Here’s the result of this first comparison:
I adjusted the white balance according to the image taken with the Color-Ultron without any filter attached (top left) so you could judge the colour cast introduced by each filter. I also did NOT change the exposure so one can make some claims about light loss.
Because of the uneven brightness on the grey card (light source pretty close but to the left of the camera results in a gradient to the right in the picture), I did some measurements in Lightroom and have the exact numbers here (coloured so you can see in what direction the shift goes):Mind you, to adjust White Balance from Daylight (5500K) to Cloudy (6500K) and Shadows (7500K) respectively, you have to increase the temperature by 1’000K each time. Therefore, a change of 100K isn’t bad at all. A small change in tint, however, will change the appearance of an image drastically, especially when skin tones are involved. Even adjusting tint by +/- 10 can mess up a portrait completely.
My UV filters, while not top of the line, are pretty neutral when it comes to the white balance, but they also swallow some light and thus require slightly longer shutter speeds. For low light photography I would therefore stay clear of UV filters and rather use a protector instead. The Skylight filter clearly belongs to the vintage stuff and should not be used on digital cameras.
A circular polarizer absorbs polarized light and can be used to annihilate reflections off of glass, paint, rocks, leaves, but not metal. It brings your photography to a whole new level when used correctly. Bryan @ the-digital-picture has some really nice examples displaying the effect.
I only have the Hoya HD CPL and the K&F CPL but you could say that these filters couldn’t be further apart. While the K&F was included in my 15$-filter set, the Hoya HD CPL costs up to 80 USD
Here are the results, with the Hoya HD CPL on the Samyang 35/1.4 and the K&F CPL on the Color-Ultron. Both lenses were adjusted for white balance and then I took a few shots with the filter attached using the same values.
I did take pictures at three different settings (0°, 90° and 180° on the Polarizer) to see if there would be variable results but all the values turned out to be identical.
The Hoya HD CPL wins in all tested disciplines but not as clearly as many might have expected. However, I’m really curious to find out how these filters will handle flaring.
Included in the K&F filters set were filters labeled ND2, ND4 and ND8. My Cokin P copy, the TIAN YA slide filter set has filters that seem to be ND2, ND4 and ND8 as well, along with the coloured and the neutral gradation filters.
Because ND-filters are very confusingly named with identical numbers meaning different things for different companies, here’s what these filters are supposed to do:
ND2 – doubles the shutter time, so it swallows 1 stop of light
ND4 – increase shutter time by a factor of 4, thus swallowing 2 stops of light
ND8 – multiply shutter time by 8, taking 3 stops of light
On the other hand, the ND3.0 on the Haida filter means 10³ and therefore it should increase the shutter time by a factor of 1’000, thus swallowing 10 stops of light.
You often hear/read arguments against cheap ND filters because they supposedly introduce bad colour casts. I couldn’t care less, because you can easily remove those by shooting RAW and correcting the white balance in post processing. Heck, I could even remove the colour casts introduced by the radioactive lenses in post processing ( article about color casts).
Now here’s the pictures for the K&F ND-filters on the Color-Ultron:
And here are the pictures for the TIAN YA ND-filters on the Samyang 35mm f/1.4:
Here are the numbers:
Temperature-wise, all the filters cool down the image somewhat, with the darker specimen being really cool. Looking at the tint, the situation is really okay and can easily be handled in post processing.
The most interesting thing, however, is the brightness. The ND2 filters both don’t get you a full stop, thus I’d rather use one of the polarizers for that effect. The ND4 are quite close to their target of 2 stops, but the ND8 clearly overshoot their target of 3.0 by a half stop.
Special ND filters
This is the TIAN YA ND Grad shot through the middle (approx.), through the clear side and through the dark side (ND2).
Here are the numbers:
While the temperature varies only by 100K from top to bottom, the difference in tint measures 20! This means that you can either have a purple-ish sky or a greenish foreground, but without time-consuming measures to adjust white balance for upper and lower image areas separately you won’t be able to use this filter properly.
And here’s the Haida 10-stop filter. What do you need a 10-stop filter for, many may wonder. Usually these filters are used to really, really blur water or clouds passing by in landscape photography, because the shutter time is increased by a factor of 1’000 when you use such a filter (Meaning a shutter speed of 0,5″ becomes >8 minutes, e.g.). You can also use such a filter to get rid of people in a crowded place, which is what I’d like to do some time in the very near future (I will show the results in a future article and write some words about the process of course).
I shot the unfiltered image at iso 100, f/5.6 and 0.4″ shutter speed. In Lightroom I reduced the exposure by 1 stop. I adjusted the settings in camera and later on in Lightroom to achieve the same brightness for the filtered image.
In reality, the image with the Haida-filter would be ~800x darker than the unfiltered image.
Obviously, it’s green:
However, the colour temperature remains unchanged and the tint can easily be removed in Lightroom.
In the second part I will look at how the filters handle flaring from a light source in the frame. Read on here, if I caught your interest.