Thursday, August 4, 2016

Filter Galore…

The toys are finally here, and it is that time of the year! Even though it is hot outside but I have to cope a little and check the results of "playing" with my new toys.
As a brief for what I've ordered before, here is a list:
  • UV-cut gel (polyster) filter.
  • IR-pass gel (polyster) filter.
  • Solar filter.
  • Hot Mirror circular filter.
  • Motorized tripod head.
There are other stuff but no need to list them right now until comes to talk about them. This set of filters is the core of my testing this week, beside the motorized head. The hot mirror (or IR-cut) filter is of interest for me because I'm intending to use it with my B+W Black 403 filter, which passes Ultraviolet, but has a considerable leak in the infrared region as well, and here comes the hot mirror part: to block infrared from reaching the B+W filter.


In the beginning, I've tried to test a combination of various sets of filters against a tungsten lamp, but realized later after some research that tungsten lamps, despite being a good source for infrared, but are not good sources for ultraviolet. Moreover, and probably because I was shooting the source directly, the images of the tungsten lamp with stacked circular filters suffered internal reflections. It looked good though!

Consequences of internal reflections in between the filters stack (in the circle).

For this reason, I had to think of shooting a reflective surface, and under the sun of course since the sun is source #1 for ultraviolet. Even though most of my lenses are not specialized for ultraviolet and do have some coating, but I carried on the tests with both cameras; converted and unconverted (regular) one. The interesting part was done with the converted camera, while for the unconverted camera, I just wanted to see and check how UV-cut and IR-Cut filters do affect the image. We'll come to that later.


Since I barely have time to do what I want to do at home (specially after coming back home from work with a wrecked body because of the heat), I decided that it is best to pick my stuff with me to my workplace and try to test these filters by shooting some green foliage around the place. Even though none of my lenses is prepared for ultraviolet shooting but the results were somewhat significant. I decided to work without calibrating the White Balance (like I did when shooting the tungsten lamp) and to avoid any dragging (changing focus or zoom by mistake) I've used 50mm f/1.4 lens, affixed at f/11.

Click to enlarge.
Legend: Null=no filter, UVC=UV-Cut, IRC=IR-Cut, IRP=IR-Pass, UVP=UV-Pass.
Plain=camera and lens without any pass filter applied.

As can be seen from the comparison table above, I've organized the work by shooting with the camera and lens plainly, then applying the pass filters gradually, and by the end, applying both pass filters with each other. In every trial, the band-cut filters were applied; single and together by the end. As I stated before, the White Balance was not calibrated and it was not changed later when editing the RAW format, but I did some work with it later on to compare some results in particular. The color space was fixed to Adobe 1998 (unlike my usual way to work in ProPhoto). I'll try to navigate through some particular observations in order:
  1. Using the filters first on the lens directly, it is noticed that UVC doesn't do much, but IRC gets the image closer to the real colors, and adding UVC later probably makes it darker a bit and maybe closer further to the real colors. The image still reddish after adding the hot mirror (i.e. IRC), and probably this is caused by the fact that the hot mirror starts blocking infrared only at 700nm, while some considerable amount of infrared do in fact exist before this range as well (at around 650nm, in some instances).
  2. Using IRP on lens and then applying the filters again, probably emphasizes the fact that the hot mirror does leak a bit of infrared further. My B+W 092 filter starts its transmission at around 650nm. It is noticed that the image gets darker and redder as IRC was added. UVC did not change much features significantly, either alone or with IRC.
  3. Using UVP on lens and applying the filters again shows again that UVC didn't have much effect in fact, and the hot mirror blocked some infrared indeed and the image becomes darker. That doesn't mean we are looking at pure UV image though, since we have the coating on the lens and the UVP filter does leak IR a bit before 700nm, and thus in between that range we would still be looking at a tiny amount of infrared still.
  4. Combining the two pass filters here, IR and UV, and applying filters on them, provided some unique looks, specially with IRC. The whole scene turned into something like a X-Ray slide but in red, with edges being brightly the most. UVC didn't add much here though but it did contribute a little to the image brightness (i.e. reduce it a bit further). It's hard to notice with first glance maybe.
Away from these results, a quick inspection for all these sets after fixing the white balance in the RAW file, yielded some interesting results, such as that shots taken with IRC filter on (excluding the plain shots) tend to be yellowish in general, and shots where UVC is involved tend to remove some bluish streaks slightly and lighten the shadows a bit.


With my unconverted (i.e. regular) Canon EOS 7D, not much was noticed using UVC and IRC filters; not even the very old 18-55mm lens. However, of interest to me, was the UV gel (or polyster) filter which I've purchased specifically to be used with fisheye lenses, specifically Canon EF 15mm f/2.8 fisheye lens, which is my main tool for making panoramas.

Kylemore Abbey
Notice the bluish streak on the mountains.
 As it can be seen here with this example above, getting bluish streaks is common with my work, and beside the chromatic aberrations, these blue tints can be really troublesome to fix, specially when the work done involves HDR technique. For this reason, I was hoping that LEE UV-2B Resin Filter would be the solution for this. In fact, to my understanding, the UV-2B works on a range of wavelengths different than that of the circular UVC (scientifically, UV is divided to 3 bands: A, B, and C, but seems the naming is irrelevant to this). According to the description provided on B&H website, it is mentioned that it is "... useful for high altitude photography and eliminates almost all UV present..."

Click to enlarge
A: with UV-2B filter.
B: without filter.
Looking carefully at the two shots above, it can be seen that the grass and shadows are brighter when shot using the UV-2B filter. Notice that the two exposures are the same, at 1/200sec. Moreover, upon a close-up check, this filter greatly reduced the bluish haze around the branches; and this is a problem which I usually suffer from when shooting a panorama outside with trees or fine objects against the sky.

Click to enlarge
200% zoom of the branches.
Left: with filter
Right: without filter.

In zoomed portion above, notice how the blue streak around the branches on the right, is reduced on the left. Also, the shaded area of the tree or bush looks brighter with the filter. This blue streak around fine branches is a major problem when applying HDR technique and doing panoramas in general. Many panoramas had this strong bluish glow around fine objects set up against the blue sky. I'm hoping this filter will be the salvage for some of my problems with colors when doing panoramas. I've made a square piece for my Canon fisheye lens, and probably will make another one for my Rokinon 8mm fisheye lens as well, even though I didn't test the filter with this lens yet, which has a stronger distortion. Would this filter be useful in reducing chromatic aberration as well? Though logically they are not connected, but since the filter acts in the blue range, it might help with its reduction.

100% crop of a panorama done in Cahir, Co. Tipperary, in 2010.
Notice the purple and blue streaks around the branches.
The situation became catastrophic further with sharpening!
Could the UV-2B filter enhance such panorama and make it better?

Now with all these results, it is time to pick up a project and work on something to discover more about these filters; specially the UVP and IRC combination, and also using the UV-2B gel filter for regular panoramas.
Along the line, I'm researching the possibilities of putting my old useless lenses to use back again by adjusting them for UV Photography, as it seems there is some specific way to remove the coating from the lens front element. Not sure if the rest of the elements do have special coatings as well but I might as well research that to see. There are 3 main lenses which are kept aside; two of them because of damage and one because of its old age and little malfunctioning: Tamron 70-300mm (broken), Canon EF 55-200mm kit lens (broken), 18-55mm kit lens (malfunctioning). Some "adventurers" talk about the use of chemicals to remove such coatings and some speak of rather physical activity (like using sandpaper?) to remove the topmost layer of the lens front. I think it is worth a try, since these lenses are just taking some place and I hate to throw them out just like that. I think it is the time now for them to be useful for little experimenting!


With these tiny experiments, still more to come, as I need to test the IR gel filters, and the solar filters (tried some but no success). The motorized head had gone some testing too, and it is a valuable tool but has some cumbersome sides to it, which I might address in a review on B&H.
As I'm typing these words, I've received a new email message telling me that another panorama was chosen as an Editor's Pick for 360Cities website. This is the second time in around a week or so since my other panorama from Oman was picked as well. This looks promising, even though the panorama didn't appear yet in the Picks section of the website yet.

Inside The Victorian (B&B)

There is a call which I hope I can discover or try soon,  and that is the aerial panorama. I'm not sure how it is done, but if it involves the usage of those new 360 cameras to take the whole space, I might as well skip the idea. A drone is out of question for the time being, but it needs a further investigation to see what's behind such a trend!

With summer getting on my nerves already, and the seemingly becoming-harder life in here, makes me wish to travel as soon as possible and putting a burden on my budget. There is a vacuum in the heart, yet I'm not sure how to fill it. I'm tired…

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