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I just bought a old Minolta MD Zoom 35-135mm 1:3.5-4.5 lens together with two old Minolta SLRs to get into film photography.

Before using actual film I adapted it to my Canon 600D (using a no-name MD-EOS adapter) to play around with the lens. I quickly noticed a blue glare/flare in the center of the image. I then noticed that it is the opening of the aperture I see in the photos. See the example shots below were I opened the aperture from f32 downwards.

Why is the aperture showing up and can I prevent that?

Will this also show up when using the SLRs it was built for?

f32 f32 f22 f22 f16 f16

(...)

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  • \$\begingroup\$ It looks like this is happening on a cloudy day — the sun isn't just out of frame, right? Is it always right in the center? Does it decrease if you use a lens hood? \$\endgroup\$
    – mattdm
    May 19, 2018 at 16:54
  • \$\begingroup\$ @mattdm No, these fotos were taken looking south while the sun was very low in the west. The sun wasn´t even visible were I was standing. I didn´t have the lens hood on but I will try it and report any difference. \$\endgroup\$
    – asquared
    May 19, 2018 at 17:43

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Yes, that's because the adapter you're using - it is not possible to adapt Minolta MC/MD lenses to Canon EF while retaining focus to infinity without an adapter that has corrective optics (and additional crop factor) due to focal flange distance of Minolta mount. So what you see is a reflection of the adapter glass element. I've never seen reflection like that on properly used lens on the same mount camera, I've been using Minolta mount cameras and lenses for quite some time. Have no fear, there would be no issues like that on a proper film camera. You could try the lens on any mirrorless camera, they are a much better choice for adapting Minolta lenses than any DSLR out there.

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This looks to me like reflection from the sensor to the rear element and back again. Film is less reflective than digital sensors so some older lenses have either no anti reflective coating on the rear element or have a coating on that element which is not as effective at cutting out reflections from the sensor side.

If I'm right, this won't happen using the lens with a film SLR.

Edit: As others have pointed out in the comments, since the adapter you are using has an optical element it's most likely that this is the source of the reflections. It's likely that the coating on a cheap adapter is of inferior quality. A higher quality adapter may well not show this issue, and in any case it should not show on the original film SLR where the adapter wont be required.

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    \$\begingroup\$ I suspect it has something to do with the adapter (which has glass) not just the sensor. But I don't really know. \$\endgroup\$
    – mattdm
    May 19, 2018 at 19:56
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    \$\begingroup\$ Could be, I didn't clock that it's an optical adapter, also more likely to be either uncoated or have a poor quality coating on a cheap adapter \$\endgroup\$
    – Joseph Rogers
    May 19, 2018 at 20:04
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    \$\begingroup\$ I have seen similar effects when I was searching for a "speed booster" for Sony cameras. There was a cheap adapter available that showed such blue spots. The more expensive ones did not show this problem. Therefore I also assume it is due to insufficient coating of the lens. \$\endgroup\$
    – Gerhardh
    May 21, 2018 at 6:54

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