Using effects lens filters
Old lens filters for effects
Old lens filters – are they useful today for colour and B&W?
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After being given a stack of unusual lens filters, Keith decided to see if any were of use on a modern digital camera.
Such filters can often be found in charity shops and the like at very little cost – but do they do anything useful and what can trying them out tell you about how your camera captures images?
If you’ve used any of these in the past and have any further info, please feel free to add a comment at the foot of the article!
Assorted lens filters
The stack of filters were all 49mm, and in the spirit of always helping people dispose of spare photo kit they were inducted into my ever expanding photo-junk drawer.
49mm is a small size for any of my modern lenses, but I know that it’s what some of my ~40 year old Olympus OM lenses take, so they should happily work with my Zuiko 50/1.2 and 24/2.8 lenses on my Canon EOS RP.
These lenses work really well on a mirrorless camera like the RP [see my EOS RP review]
Split field filter
It’s essentially a close-up lens sawn in half. The filter freely rotates once fitted, so you can decide which half of your field of view gets magnified.
The effect is easy to see in this shot of me holding the filter – there is no glass on the right hand side.
First a shot taken at f/5.6 with the 24/2.8 lens, with no filter.
Pretty much the view you’d expect – focus peaking in the viewfinder of the EOS RP makes such lenses really easy to use.
Now with the magnifying effect on the left. The right side is focused normally on the big plant.
Not only has the half lens brought the point of focus closer, it has increased the focal length, making the doorway larger.
Now, if I wanted this photo doing ‘properly’ I have used the TS-E24mm tilt shift lens [TS-E24 review] and tilted the lens to the left to run the plane of focus along the length of the tripod.
However the effect is interesting and I can see how you might use it for landscape where you wanted a bit of close foreground detail (flowers?) in the shot.
It was with this filter that I was reminded of the need to avoid very small apertures, since they had the effect of making the dividing line obtrusively sharp.
Multivision 3 filter
Now this is one where I did know what I’d be getting. The lens is in the form of a thin prism, shifting the image. Actually it’s 3 prisms, giving multiple overlapping images. You get the idea in this shot of me holding the filter.
Yes, it’s the effect I remember from ‘Top of the Pops’ on TV in the 1970s
I have a great shot of Karen (three of them) eating soup, but was refused permission to show it…
So, here’s a building
Once again, the sharpness of the transitions is affected by aperture, but this effect is one I have some difficulty in seeing where I might use it in a non-ironic way…
Coloured filters for black and white
There were two coloured filters. I’ve used coloured filters with B&W film in the past, so I expect these are a way of localising the filter effects in your composition.
Coloured filters were a useful way of changing the tonality of a scene recorded on black and white film. The effects varied with the spectral sensitivity of any particular film stock and the filters (by absorbing light) required a lengthening of exposure.
The classic uses of coloured filters for B&W film was the range from light yellow though orange to red where the progressive diminution of blue light would increasingly darken blue skies
This view of the Suffolk coast at Shingle Street was taken (with the same Zuiko 24mm lens) using a light orange filter to darken the blue sky – I can’t remember what film I used.
What about coloured filters for digital cameras?
First, let’s look at a colour digital image, taken in Wyoming, where I stopped to look at the very orange rocks. The strong colours are one reason I’ve used this image for many years when talking about digital black and white photography.
For simplicity I’m using Photoshop’s B&W conversion, which offers a complex setting of colour channel strengths, as well as preset options named after common filter types.
One of the older pages on the site has a huge collection of techniques for converting colour images to B&W
This is the default B&W conversion.
A ‘green’ filter lightens the green grass areas and makes the blue sky a little darker.
A ‘Yellow’ filter setting makes the sky a lot darker, whilst those orange rocks in the foreground are rendered a lot lighter.
The ‘Red’ filter option is even more extreme, but shows up drastic pattern noise in the dark sky (you can see it in the images above). Modern cameras are a lot better but this was taken with my 11MP full-frame Canon 1Ds in 2004.
So, we have the effects of coloured filters on B&W film and the effects of digital filtering applied to a digital image captured in three colour channels (Red/Green/Blue).
What about coloured glass filters on a digital camera?
The split colour filter
At first thought, this filter should let you apply an orange filter to the sky and a green one to your landscape. Both the orange and green filters absorb some light, so ideally a longer exposure should suffice for both halves.
I’ve shown screen grabs with the B&W conversion (channel mixer) sliders for ACR, which I’m using for processing the RAW camera files.
The effect of the colour filter is obvious – as before, the selected aperture will define how sharp that boundary is.
The default B&W conversion doesn’t show much effect.
Tweaking the sliders shows a bit of an effect, but not much.
I took a few more shots with the filter boundary vertical, so as to make i more obvious what was being affected by the filtering.
Here’s a vertical version with the default B&W conversion.
Can you really see much difference?
Tweaking some of the sliders gives me a bit of the orange filter look on the right, but not in an intuitive way.
In effect, I’m trying to reproduce aspects of the spectral response of a B&W film with the sliders. However I’d note that I can do that without the coloured filter and that I’m not limited to having a 50/50 split.
So it would appear that when I told someone years ago that their filters for B&W photography wouldn’t work for digital, I was right.
The colour spot filter
This one simply has a hole in the middle.
The thickness means that with the 24mm lens I’m using, the edge of the hole is having a blurring effect on image quality.
Converting to B&W give me a ‘ring blur’ effect…
Shots at f/16, f/11, f/5.6 and f/2.8 show how a wide aperture blurs the sharp cutoff.
I suspect that the narrower field of view of the 50mm would show less of the edge of the hole, but even so, this filter is a mystery to me…
And your point was… ?
Sure, none of these filters are likely to make it into my day to day gear, but it was an interesting diversion and helped remind me of just why I used to use coloured filters with B&W film every so often.
It also reminded me again that software film emulation has some distinct limits given the RGB nature of image capture.
One more thing… It got me looking through my photo archive, there’s probably a lot of stuff in there that I’ve not properly looked at.
I’m looking to write lots more reviews and articles for the site over the coming few months. If you’ve any suggestions or topics you’d like to know more about, please do let me know – Keith
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