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10-27-2018, 08:06 PM - 1 Like   #1
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Un-Macroing my telephoto lens.

So after attempting to disassemble my Sigma λII 75-300mm and putting it back together again, it suddenly has turned into a very good Macro lens. While it does have interesting possibilities in this current state, that's not what I bought it for.

There were no leftover parts and I know that it has something to do with how the front elements are reassembled. However, I'm at a loss as to how to correct it. I am considering buying a second model as a parts source and I should be able to use it to solve the problem once I have it. However, I would like to figure out this problem before it would arrive.

Thoughts?

10-27-2018, 09:07 PM   #2
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I'm no expert. But I seem to recall that reversing an element or two can cause this.
10-28-2018, 01:41 AM   #3
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Yes, as UncleVanya says, you probably reversed an element or group. See if you can find the diagram showing the layout for this lens. If not, trial and error works. There can't be that many combinations.
10-28-2018, 08:41 AM   #4
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QuoteOriginally posted by UncleVanya Quote
I'm no expert. But I seem to recall that reversing an element or two can cause this.
It's possible since the middle group was lose and may have gotten reversed before reassembly. I never got to the point where I had removed individual lenses and only did a partial body disassembly.

It's also a telescoping zoom if that matters to those with experience.

10-28-2018, 06:39 PM   #5
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And let this be a lesson to everyone: don't say that something is broken until you test it in your camera. Turns out that you can't determine if you reassembled your lens properly by merely looking through the barrel. It was only an optical illusion and I had put it back together correctly.

Unfortunately, I only found this out when I decided to see just how good this accidental macro was on the lens. :S
10-28-2018, 08:26 PM   #6
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Glad it's working.
If you look through it at a distance greater than the registration distance I suppose it's like macro extension tubes.
10-29-2018, 06:15 AM   #7
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And just like that, this Sigma lens has caused me to add another thing to my accessory shopping list.
10-29-2018, 10:53 AM   #8
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Many years ago, I bought a Yashica tl electro with a 50mm f1.9 lens new. The lens would not focus on infinity, so it was returned immediately. It was either replaced, or repaired, the multi-start focussing thread in the lens had been assembled a couple of starts out and it wouldn't focus past about 3 feet.
I still have an old Vivitar Series 1 70-210 which had haze at the front end, so I stripped and cleaned the front lens group without realising that the infinity focus depended on fine tuning the seating depth. Fortunately, I had a film camera with a split image screen to get it adjusted and locked.

10-29-2018, 11:56 AM   #9
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Should have shared some good macro images taken with it post-mod.
10-29-2018, 12:56 PM   #10
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QuoteOriginally posted by DrMindbender Quote
And let this be a lesson to everyone: don't say that something is broken until you test it in your camera. Turns out that you can't determine if you reassembled your lens properly by merely looking through the barrel. It was only an optical illusion and I had put it back together correctly.

Unfortunately, I only found this out when I decided to see just how good this accidental macro was on the lens. :S
QuoteOriginally posted by pres589 Quote
Should have shared some good macro images taken with it post-mod.
The "mod" was a user error confusing looking at the lens unmounted. The lens wasn't changed and wasn't really macro - it was working normally the whole time.
10-29-2018, 01:22 PM   #11
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Well that's boring.
10-29-2018, 01:50 PM   #12
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QuoteOriginally posted by pres589 Quote
Well that's boring.
LOL - right???? But it's less traumatic for the OP.
10-30-2018, 05:56 AM   #13
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QuoteOriginally posted by UncleVanya Quote
LOL - right???? But it's less traumatic for the OP.
Although, I do plan to get another one of the same model to restore this lens. So I may take a stab at seeing what would happen if I were to create the error I thought I originally did.
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