Vignetting reduces as the lens is stopped down and isn't really an issue past about f2.8.ĭistortion is very well controlled. On an image shot with a Canon APS-C sensor the corners were just over 2/3 stop darker than the center. I measured approximately two stop of light falloff in the corners of the full frame with the lens wide open at f1.5. Vignetting actually isn't all that much more than most fast 85mm lenses. When the white dot is lined up with the red dot all the way on the right means that the aperture is the same as the red dot next to the aperture scale. They're not, they're just a bit confusing. Confusing? I've seen people claim that their lens has the aperture marks backwards. However you're not at f1.5, you're at f4. However you are now at f1.5, not at f4! When you rotate the aperture ring all the way to the left, the white dot on the second aperture ring lines up with a red dot at f1.5. with the first aperture ring set to f4, there's a red dot by the f4 and when the second ring is rotated fully to the right, the white dot on the second aperture ring lines up with the f4 marking and the white dot. Then, when you want to shoot, you rotate the second aperture ring all the way to the left and it will hit the stop with the aperture at the pre-set f4. Then to focus (wide open) you rotate the second aperture ring all the way to the right. If you want to shoot at f4, you set the first ring to the click stop at f4. The second aperture ring actually controls the aperture and it has no click stops. Now you might think this controls the aperture, but you'd be wrong. The short answer is yes, but read on for more details.įor those who have never used a pre-set stop down lens, the aperture control may be somewhat confusing. It's a bit trickier for Nikon shooters since a purely mechanical adapter won't give you infinity focus and an adapter with glass which allows infinity focus alters the optics a bit, so +1 for Canon here! The question is does it still have the famous "swirly Bokeh" effect. The mount is still M42, so it's very easy to adapt to any EOS DSLR. By all appearances it seems to be the same lens design they used in the 1950s, the only difference being that the new lenses don't have a tripod mount. In 2012, the KMZ factory announced that they were going to put the lens back into production, and they have. Why it does this I'll speculate on later, but it's for this effect that the lens has been sought after. Shot wide open and with the right amount of defocus on the background, the background appears to "swirl" around the subject. Why, you may ask, would someone pay $500 for a used lens that's big, heavy, inconvenient to use and not very sharp? Well, it has this "Bokeh" thing. In this configuration, though there's a red dot next to f5.6 and a white dot lines up with f5.6 and the red dot, the lens is actually set to f1.5, Confused? Keep on reading. 20 year ago you could probably pick up a used example for $50 or less, but more recently they have been selling for around $500 or more. In recent years it has also gotten quite expensive. It goes without saying that it's manual focus of course. It also uses a rather awkward pre-set stop down metering system with two aperture setting rings at the front of the lens and a rather narrow focusing ring near the back. It's not a very convenient lens since it's fairly large and built like a tank (actually probably more like a hand grenade). The published MTF/resolution(?) curve shows an odd dip with the region about 10-12mm from the center of the frame being the softest The numbers aren't impressive either with a quoted center/edge resolution of 36/17 lp/mm. It's not a sharp lens, especially when used wide open. Over the years the Helios-40(-2) has developed something of a cult following. The M39 mount -40 version seems to have been made with a "silver" finish while the -40-2 version was available in black. The lenses made during that period had a built in tripod mount. Things got a little turbulent in Russia as the Soviet Union dissolved in 1992. The production dates of the Helios-40 and Helios-40-2 are a little tricky to nail down, but they were certainly made from the mid 1950s to the early 1990s. The optical design of the Helios-40-2 (the -2 simply refers to the lens in a M42 mount rather than the original M39) is shown below: Double Gauss lenses have been used since the 1930s for fast semi-wide to short-telephoto lenses. The Helios model 40 lens is an 85mm f1.5 which is reported to be based on the Carl Zeiss Biotar design, which is basically a double Gauss lens. They were/are made in the Krasnogorsk Mechanical Works (abbreviated as KMZ) near Moscow. Well, to start with "Helios" is the brand name of a line of lenses, often sold with Russian "Zenit" cameras. What's a Helios-40-2 you may well ask, and why should I be interested in it?
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