Возвращаясь к теме о проекционном объективе ACT300 F120 1:1.6. Сделал небольшой непрофесиональный тест.
Описание на английском (извините, что без перевода).
Projection lens ACT300 F120 mm 1:1.6. Impressions.
Recently, I received the lens from a very interesting projector to make an amateur test. Theoretically, the background wash capacity (WOW 75) should be quite attractive for portraiture of the whole height.
Specifications:
- focal length: 120 mm;
- apperture: f1,6;
- shape: cylinder, outer diameter 82,5 mm, length - 113,5 mm;
- front element: diameter 74 mm;
- Rear element: diameter 55 mm.
- optical scheme: double Gauss; 4 groups, most likely 6 lenses, of which group 2 and group 3 - cemented doublets (see photo).
- Weight: 1190 g.
- working distance (about 70 mm from the back of the body and about 80 mm from the rear element to the focal plane (objektat infinity).
After evaluating the physical parameters and the most frequent DSLR flange focal distance parameters, there are about 23.5-26 mm of gap for mounting the focusing mechanism. Mirrorless camera - even more.
So, as said my collegue photographer, if the lens was not tested for a portrait, it's not a lens yet :). I wanted to try it, because in fact, the Internet managed to find just two portraits.
To do this, I needed some adapters and helicoid, as well as mirrorless FF camera. With my existing adapters I got a pretty big design, but I'm sure it can be made more comfortable.
The first attempts were made at home to evaluate background bokeh at different f values (using an adapter with iris aperture): f1.6; f2.0; f2.8; f4.0; f5.6. 100 percent crops at f1.6; f2.0; f2.8; f4.0; f5.6 give an impression of the sharpness changes. To compare the sharpness and chromatic aberrations at the open aperture, I chose for comparison the 35KP-1.8/120 projection lens and Visionar 141/1.9 projection lens. Pictures taken with Pentax K-1 (36 Mpix).
Subjective impression: The ACT300 F120 1: 1.6 at the open apperture is soft, 35KP-1.8/120 is sharper in the center and Visionar 141/1.9 is even sharper. ACT300 F120 1:1.6 at the open apperture behaves fairly well with chromatic aberrations in the center and in the periphery of the frame, purple fringing is visible but not very extensive. Meanwhile, the 35KP-1.8/120 shows green and red CA‘s in the center, while the periphery also shows red CAs. Visionar 141/1.9 is in the middle by intensity of CAs, but more contrasty.
And in the end you can see some street portraits made by the Sony a7II FF 24 Mpix camera and ACT300 F120 1:1.6 at open aperture. Photo unmodified, not sharpened. A fairly long blend has been used, so the vignetting is visible in the corners.