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Tuesday, August 26, 2014

Optical test

Moving on with the tests on my latest lens the Samyang 500 mm f/6.3, here is a very objective comparison to give an idea of the level of magnification and optical performance this cheap lens is capable of. 

The photo below is a 100% crop from Castelo de São Jorge in Lisbon at a distance of 700 meters (taken from the Miradouro da Arco da Rua Augusta) showing the portuguese flag on the left and the city hall flag on the right. It was taken with a 35mm f/1.8 Nikon AF-S G prime lens (for DX). The settings were ISO 100, f/8 aperture and an exposure time of 1/250 seconds.

The photo below shows the same two flags but taken with the Samyang 500 mm f/6.3 at a distance of 6250 meters (measured with the Google Earth ruler). This last photo was taken during a calm windless night with the 2x teleconverter, yelding a focal length of 1000mm and an aperture of f/12.6. The selected sensitivity was ISO 200, and an exposure time of 20 seconds was used.

By comparing the pixel coverage of the same objects in both crops we can see that in spite of the 10x greater distance, these objects appear 3x larger. By doing simple math this means that we have roughly 30x magnification in respect to the 35 mm lens. 

If we calculate from the lens reported focal lengths, we get Mag = 1000 / 35 = 28,57x. This is quite close to the first estimate based on the distances and pixel coverages.

Even though it is not a fair comparison putting side by side entirely different lenses and commenting the different levels of sharpness (it is like comparing a scalpel to a chain saw in terms of cutting accuracy), I must say that given the low cost of the Samyang lens, the contribution of atmospheric artifacts, and the large magnification, the overall result is very sharp given the dimension of the challenges that are implied in photographing under these conditions.

Saturday, August 23, 2014


Satisfaction with the 500mm reflex lens increases as I explore its potential in different situations. This time I took a number of shots holding it by hand during an afternoon next to the Lisbon international airport main runway. It was quite a challenge because of the moving targets, the lens being a pain to focus, and the fact that the camera was being held by hand. But the results seem to tell the rest...

To finish this topic full circle, here is a bit of cruise ship spotting, from the comfort of my balcony. These photos and videos were taken with a tripod and the 2x teleconverter added, resulting in a focal length of 1000 mm:

Wednesday, August 20, 2014

World Photography Day

Coincidentally, after having purchased an exotic lens for my camera and some days of wait for the F-Mount adapter, yesterday during the World Photography Day, I finally managed to test the lens. Aware of the shortcomings of this lens, still I was very pleased with the results, which I must say, open doors to different types of photographic work.

The lens is a Samyang 500mm f/6.3 mirror prime:

It doesn't have autofocus, zoom or diaphragm. It is a pretty frugal design, just like a catadioptric telescope with a camera mount instead of an eyepiece. It is hard to focus given its small depth of field for the focal distance and the travel range of the focus ring. Many people don't like it's donut shaped bokeh. But still I found it a very interesting lens for its focal length, size and reasonable speed. It basically can do what no other 150 Euro lens can do. And sometimes getting a great shot is not about the bokeh, the sharpness, contrast, etc, but about simply getting the shot, capturing the moment, telling the story.

While not having had much time to perfection the shooting, I have made a few shots taking advantage of the view around my balcony, which covers a little bit of Almada, the Tagus river and Lisbon.

Train station, at about 600 meters of distance:

Old Almada, about 3 Km away:

Panteão Nacional (mausoleum), about 7 km away:

Soccer field lamp, 500 meters away:

Church inside Lisbon, about 7 km far:

In the field of astrophotography the lens capabilities are yet to be tested. The area where I live is complicated because of the heavy light polution of the cities nearby.