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BPD_1938

Playing with the light. ND Filters.

Most good modern DSLR’s have a good amount of Dynamic Range (DR), DRĀ is the measurement from the brightest to the darkest a sensor can capture in one image, beyond this range highlights will be blown and dark shadows will yield no detail. It is normally measured in Exposue Values (EV). A Good sensor will be at least 12, and maybe as high as 16.

But what do you do if the image you are trying to capture has more DR than my sensor can capture? Well there are a number of ways to deal with this, these are the most common:

  • Take multiple exposures to combine into one image, either as a composite merge or a high dynamic range shot (HDR), later models can do HDR in camera.
  • Add additional light to the scene.
  • Use filtering effects to modify the light being exposed.

BPD_1948HDR and adding light are fairly common, but using filters is not very common for night sky photography and Aurora’s. The reason it is not popular is that adding filters reduces the amount of light entering the camera, resulting in either having to use higher ISO settings or longer exposures.

However given the right circumstances using a filter can have great results. I like to use them for shooting Aurora’s provided the Aurora is very bright and it has minimal movement. If the Aurora is bright I don’t need to increase my ISO, and minimal movement like beams in the Aurora will mean I can increase the exposure time a little without blurring any details.

I have found that using a 0.9 (3 stop filter) helps significantly with exposure compensation, balancing out the light Aurora in the sky to darker foregrounds. Not only does it help with the balance and bringing out blacks, but it effectively gives your sensor a 3 stop advantage.

A sensor that can shoot 14 stops of DR is suddenly equivalent to 17.

Suddenly I’m no longer dealing with those horrible black dark areas where the noise hides.

FOTGA Fader (Variable) ND

Recently I read a few reviews that indicated that the FOTGA ND 8 Stop was a good fader or variable ND filter, and should be considered for landscape work. Most information I read gave it favorable reviews with the only draw back being the typical black “cross” you get when using it to the extreme.

So here are the results from my testing:

Camera: Canon 6D with Canon 16-35mm f2.8 II + FOTGA Slim Wide Band Fader ND (W) 82mm.

Settings: Manual Focus, Av Mode, f5.6, 100 ISO.

The filter was tested at 16mm, 24mm and 35mm, with the filter set at Min, 1/4, 1/2 and 3/4.
It should be noted that the marks on the fader mean nothing, so I have also indicated the strength based on the camera shutter speed equating them to the closest f-stop(s) of light reduction when compared to no filter.

Post processing: All of the images were imported into light room 4.6, and had lens correction applied to ensure that the standard lens vignetting was removed. For the purposes of the test I was not concerned with sharpness or color balance.

Results & Conclusion:

FOTGA

I think the results speak for itself, for me with a full frame camera (6D) and a good wide lens, suitable for landscapes the results were terrible, bad copy? fake cheap knockoff? maybe, but I doubt it. In my option this filter is only useful on the min setting or 2 stops, beyond that significant vignetting is introduced. It may work better at focal lengths beyond 35mm, and when I get a step up ring I will trial it on longer focal lengths.

Bottom line this filter is not suitable for landscapes.

How is the Samyang 14mm going?

So I have had the Samyang for more than a while now, and I thought I’d give some more feedback. Firstly I must say this lens is SUPER sharp, at f5.6 it is incredible.

What I am finding however is that the distortion plug-in for Adobe Lightroom is not perfect, and I’m still left with a little distortion which is a little bit frustrating. Probably more me looking for the issue, knowing it’s there. However it would not be easily seen in most shots.

I am finding the fixed hood and no front thread very frustrating, and I long to use my ND grads and variable ND filter. To that end the Canon 14mm or any other brand at 14mm would have the same issues, so I think it still warrants having a 17-40mm or 16-35mm lens as well, maybe even a 20mm f2.8. I have managed to salvage most shots where an ND Grad would have been useful, like this one I took recently in Perth.

Still, I can’t complain given the cost…