Sunglass Filter Stacks (IR+Visible)

[eye4invisible]

Reading through various online photography articles, I often hear that ND filters are "sunglasses for the camera".

 

Thing is, not all sunglasses are created equal. Variations in coatings means that, unlike true ND filters, sunglasses often create a colour cast, so I was curious to see how this would affect a full spectrum camera (given how sunglasses are generally transparent to IR light, depending on how deep you go into the IR). How would the sensor render through a green-tinted sunglass lens vs a brown-tinted one vs a neutral one?

 

So, I bought a bunch of el-cheapo sunglasses with circular frames and 54mm diameter lenses, and a bunch of 55mm UV filters in order to mount them in (to avoid light spills from unfiltered visible light and to avoid vignetting). Unfortunately, I ran out of UV filter rings due to my previous experiments with the dichroic glass filters, and then the coronavirus hit China. Fast-forward 3 months later, and my consignment of filters finally arrived.

 

This weekend finally brought the sunny weather I was needing (with enough clouds to make things interesting) however we've been instructed to stay at home as much as possible, so the only shots I could take were from my balcony. That said, it did give enough variation in reflective materials (buildings, road, evergreen trees, grass and cars).

 

In total, I shot various combinations of reflective blue sunglasses (subtle brownish cast) and reflective orange sunglasses (subtle greenish cast) and/or black sunglasses (somewhat neutral in cast):

 

Additionally, I tried combinations of sunglasses in front of the camera with no other filter, with a hot mirror filter, with a KV 365nm filter (to check for UV blocking ability) for a total of about 2 dozen shots. Custom white balance was done against a piece of white paper after each change of filter.

 

I won't post every single combination, as I'll most likely run out of quota space, but I'll post the more interesting ones.

 

These are all shot with my full spectrum Sony A7 with 28-70mm kit lens, and are all SOOC jpegs (raw converted to jpeg in Sony Imaging Edge 'Edit' application). Only change is to reduce the image to 10% of the original size of 6000x4000px, and to compress it to save space). No other editing done.

 

First up is a visible shot, for reference purposes only:

 

Single strength blue sunglass filter:

 

Double strength blue sunglass filter (held in place with finger-tip). Reminds me a bit of 590nm:

 

Single strength orange sunglass filter, pink foliage:

 

Double strength orange sunglass filter, foliage is more mauve, more definition in the clouds:

 

I stacked an orange and blue sunglass filter, which ended up looking a lot like the double-stacked blue sunglass image with a slightly different hue to the sky.

 

For the black/neutral sunglass filter, I went straight to double strength:

 

Was interested to see what would happen if I stacked one of the sunglass filters with a B+W 403. Here's the unstacked image:

 

Here's the B+W 403 stacked with the orange sunglass filter. Basically turned the image monochrome, allowing just a hint of blue through:

 

And, finally, because this is UV Photograpy, here's a stack of the KV 365nm filter and the orange sunglass filter. A 30 second exposure (sorry, forgot to lock the focus!):

 

My personal favourite out of the lot was probably the double strength orange sunglass filter, for the mauve foliage and somewhat aqua sky colours it rendered. I suspect, though, that it'll be a harsh filter for photographing people. More to come on that another day, when stay-at-home is no longer required!

[Cadmium]

Andy, Cool! My personal favorite out of them is the single strength orange, with the slightly pink/red grass.

[dabateman]

That single strength blue looked to invert grass and pavement to me. Had to double check from top why cars were on the grass.

 

Interesting effects.

[colinbm]

Pretty cool.....Andy

[eye4invisible]

That single strength blue looked to invert grass and pavement to me. Had to double check from top why cars were on the grass.

 

Interesting effects.

That might just be due to the resolution of the photo. The pale turquoise of the grass is close to the grey of the asphalt, and that parking lot is oddly-shaped :)

[eye4invisible]

Andy, Cool! My personal favorite out of them is the single strength orange, with the slightly pink/red grass.

Thanks, Steve.

 

It did occur to me after posting this that sunglasses are generally polarised, so the tones may have changed due to mixed polorisation vs strength of glasses. That's an experiment for another day, though.

[JMC]

Funky. I remember seeing some work done a while ago, looking at UV transmission by sunglasses, and and was shocked by how bad some of them were at blocking UV.

[eye4invisible]

Funky. I remember seeing some work done a while ago, looking at UV transmission by sunglasses, and and was shocked by how bad some of them were at blocking UV.

I always guessed that all sunglasses were polycarbonate, so blocked UV by default, not because they're dark. I guess the UV leaky ones are made from some other plastic.

[JMC]

Andy, typically I can't find the original article I saw now, but I did find this one;

 

https://journals.lww.com/optvissci/FullText/2019/07000/Spectral_Evaluation_of_Eyeglass_Blocking.8.aspx