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A history of Sony Alpha - Minolta AF 50 mm f/1.7 versus Sony DT 50 mm f/1.8 SAM

1 December 2009
Szymon Starczewski

9. Ghosting, flares and transmission

As we have tested both lenses on a spectrophotometer, we can present their transmission curves.

A history of Sony Alpha - Minolta AF 50 mm f/1.7 versus Sony DT 50 mm f/1.8 SAM - Ghosting, flares and transmission

The Minolta fares very well for a 20-year-old construction. In the middle of the visible spectrum both lenses, with the results at the level of 93-94 %, perform neck and neck. In the red part of the spectrum the Minolta slightly prevails. In the case of the blue and purple light the Sony has the upper hand for a change. Generally the graph looks a tad better for the Sony as it is more flat, the transmission over 90% is achieved in a larger range of the spectrum so the colours are reproduced better. The difference between both devices is rather slight, though, and it would be difficult to see it in real-life photos.


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What about the flares? Apart from the transmission, measured for the light falling along the optical axis we must take into account other factors like the transmission of light falling at an angle and the design of the lens itself, including its internal blackening. First let’s have a look at the results of the Minolta.


A history of Sony Alpha - Minolta AF 50 mm f/1.7 versus Sony DT 50 mm f/1.8 SAM - Ghosting, flares and transmission

A history of Sony Alpha - Minolta AF 50 mm f/1.7 versus Sony DT 50 mm f/1.8 SAM - Ghosting, flares and transmission

As you see, you can catch some light artifacts. It is slightly easier near the maximum relative aperture, where the unwanted flares are a bit more intense.

Let’s check how the Sony fares in the same conditions. The appropriate photos are presented below.

A history of Sony Alpha - Minolta AF 50 mm f/1.7 versus Sony DT 50 mm f/1.8 SAM - Ghosting, flares and transmission

A history of Sony Alpha - Minolta AF 50 mm f/1.7 versus Sony DT 50 mm f/1.8 SAM - Ghosting, flares and transmission

It is clear that the newer Sony construction works more efficiently here. In its case the light artifacts are very weak and difficult to notice.