DM-3 2.8/78 Review
DM-3 2.8/78 (Russian ДМ-3 2,8/78) is a projection lens for overhead projectors "Sputnik" and "Sputnik-2." Designed to project slides in size 24x36 cm. Produced on the Azov optical-mechanical plant in USSR. Optical design of the lens is Triplet. The lens is manufactured with different design frames. There are also similar lens DM-2 2.8/78, differences, except in the title is hard to find. Lenses of triplet optical design interest for art photography, it is characterized by the formation of large bubbles in bokeh. But each lens is still different character. Projection lenses with a Triplet design released a lot with various modifications.
DM-3 2.8/78 Handling
The lens has a tiny size. The barrel is made of metal. front ring has a width of 1 cm to the design of the "Zebra" for which the lens moves hands in mine overhead projector to focusing.
The lens length is 35 mm.
Barrel diameter 40 mm in the front and rear 28mm. Hood, unfortunately, the lens does not have.
Mounting DM-3 2.8/78 to the Photo Camera
I mount the lens on Nikon D3100 camera using a helicoid from the Helios 44-2. The lens is placed in the margin of the internal hole in the barrel of Helios. To it fits tightly, I wrapped it with electric tape.
Mounting on Nikon D3100
This method is suitable for testing only. For serious use of the lens, you need to come up with something more reliable. To compensate for the flange distance I added a small M42 extension ring, and annexed the entire structure through an adapter M42-Nikon.
DM-3 2.8/78 Example Photos
All examples were made on Nikon D3100. RAW export without any post-processing.
DM-3 2.8/78 Sharpness
The lens has a low sharpness.
I have previously used Triplet 2.8/78, which is designed for the format 6x6 cm. So, the sharpness of the DM-3 seemed to me no better, and sometimes worse than Triplet. Although the logic of small-format lenses have better sharpness than the medium format.
The examples can be seen on the field spread. I focused the lens on the green dot. Maybe the problem is that it is difficult to hit the focus. In any case, the practical use of lens sharpness is not great.
DM-3 2.8/78 Character and Bokeh
I did not find in this lens of some highlights. Spherical aberration at the DM-3 is less than the Triplet 2.8/78, and it deprives certain artistic drawing.
Yes, you can catch bubbles in bokeh and this is probably the only advantage in the character. But even they have something rude.
I do not like the transition from the sharpness in a blur, it is a technical one.
Maybe it's subjective feelings, for some genres it goes, but it takes portraits I did not like.
DM-3 2.8/78 Color Reproduction and Contrast
Lens has a single-layer purple coating. Because the lens does not have a hood, it was afraid backlit and side light, catches flare.
But when the frame does not have a strong light source, the contrast is good, colors are also good.
Landscapes are soft, reminiscent of the painting.
Summary DM-3 2.8/78 in the photography does not show anything special. Lens without pretensions to art. In sharpness it weak, but also to the soft-focus lens, it does not hold a character. Triplet 2.8/78 I liked more.