{"id":805,"date":"2015-07-25T20:22:25","date_gmt":"2015-07-25T19:22:25","guid":{"rendered":"http:\/\/phillipreeve.net\/blog\/?p=805"},"modified":"2024-04-21T14:58:44","modified_gmt":"2024-04-21T13:58:44","slug":"defects-manual-lenses-lens-buing-advice","status":"publish","type":"post","link":"https:\/\/phillipreeve.net\/blog\/defects-manual-lenses-lens-buing-advice\/","title":{"rendered":"Defects in Manual Lenses and lens buying advice"},"content":{"rendered":"

This blog is mostly about manual lenses<\/a> which are usually 30 to 50 years old. And while most of them are surprisingly reliable the are a few things you should check before or after buying a lens.<\/p>\n

This checklist is based on the\u00a0experience\u00a0I gained from buying \u00a0more than a hundred lenses since I discovered how much fun it is to use them on Sony’s Alpha cameras.<\/p>\n

If you have additional info about a defect not listed or disagree with my assessment please leave a comment!<\/p>\n

Scratches on the lenses<\/h1>\n
\"kratzer\"<\/a>
a large scratch on the front lens of a AI-S Nikon 4.5\/300<\/figcaption><\/figure>\n

Use a large light source like a window and place the lens between you and the light so that you can see the colorful coating of the lens.<\/p>\n

Scratches are seldom a problem in the real world but they lower the resale value of a lens. In theory they could reduce the contrast of a lens or cause some flare but I have never seen that happen.<\/p>\n

You can’t really do anything to restore coatings but it sometimes makes sense to fill larger scratches with black paint to avoid light scattering.<\/p>\n

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Oil on the aperture<\/h1>\n
\"SONY<\/a>
Oil on the aperture blades of a Minolta MC 2.5\/100 – the cleaning\u00a0was very easy<\/figcaption><\/figure>\n

Quite a few older lenses suffer from oil on the aperture blades. Close you aperture as far as possible and have a look at the aperture blades. They should be dry and free from oil. If they look like in the image above it is likely that they will open and close slowly.<\/p>\n

Using\u00a0a lens with an\u00a0oily\u00a0aperture on a mirrorless camera is not a\u00a0problem because you meter and focus with the aperture already closed. I use the lens in the picture regularly.<\/p>\n

On a classic SLR it will be a problem because the camera will meter and focus with the aperture opened and the aperture will be stopped down the moment you press the shutter button. But because the aperture is slow to close your images will be overexposed and and not stopped down as far as you wanted<\/p>\n

It depends a lot on the lens but in general cleaning the aperture requires less skill than other repairs. Apertures are often quite easiy to access and you can clean them with Isopropyl alcohol<\/a>\u00a0(affiliate link). Optimally you clean the whole aperture assembly because that’s were the oil is coming from, just cleaning the visible part will only do in light cases.
\nBut be careful to document every step of the dis-assembly and be warned that it is often hard to reassemble an aperture assembly \u00a0once the aperture blades have been scattered over your carpet (I am speaking from experience \ud83d\ude09 ).<\/p>\n

\"Disassembled<\/a>
Disassembled Minolta MC 1.2\/58 , Aperture Assembly top row, second from the right by Maury Jacks<\/figcaption><\/figure>\n

Dust<\/strong><\/h1>\n

You will find dust in about any lens and unless there are huge amounts of it dust won’t affect your image quality<\/a>.<\/p>\n

You or a technican can open a lens, clean all the elements and reassemble it but I wouldn’t bother unless there are some defects like sticky lubricants.<\/p>\n

Fungus<\/h1>\n
\"dungus\"<\/a>
Fungus inside a Minolta MC 1.8\/35<\/figcaption><\/figure>\n

Fungus isn’t always easy to see because it is inside the lens. You can easily spot it if you shine a flashlight trough the lens.<\/p>\n

Fungus looks like many little roots which grow on the lens surfaces.<\/p>\n

Here is an image I took with the same lens:<\/p>\n

In my experience you still can use many lenses which are not too badly affected. They have a little less contrast but you wouldn’t notice it if you didn’t look for it.<\/p>\n

Often\u00a0fungus can be removed without any traces with a hydrogen peroxide solution but this requires quite a bit of skill and special tool because the lens has to be disassembled. \u00a0Many repair centers don’t accept infected lenses.
\nThere are certain fungi which damage the coatings or the lenses themselves so that a lens can’t be fully repaired.<\/p>\n

According to Zeiss<\/a> fungus will grow under these conditions:<\/p>\n