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Sigma 600mm f/8 Mirror with issues
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PostPosted: Sat Sep 22, 2018 1:41 am    Post subject: Reply with quote
woodrim wrote:





To me it's simply bad bokeh typical of mirror lenses.


PostPosted: Sat Sep 22, 2018 3:42 am    Post subject: Reply with quote
Interesting. Be sure to keep us apprised of this and whether the filter had been misaligned.


PostPosted: Wed Sep 26, 2018 2:46 am    Post subject: Reply with quote
Michael: Starting to get the hang of it with the Sigma 400mm...





PostPosted: Thu Sep 27, 2018 1:38 am    Post subject: Reply with quote
woodrim wrote:
Michael: Starting to get the hang of it with the Sigma 400mm...





Sweet! jt


PostPosted: Thu Sep 27, 2018 1:49 pm    Post subject: Reply with quote
Woodrim, it looks to me that this image doubling on the sides only occurs with out of focus subjects. There's that one image where an iris (I guess it is) is in fairly close focus, and it's located at the very side, yet it doesn't exhibit doubling. I notice in other images where there is doubling at the center of the frame in OOF images, so this doubling might just be an artifact of this lens's construction.


PostPosted: Thu Sep 27, 2018 2:13 pm    Post subject: Reply with quote
Michael: Yes, OOF areas and that may be a mirror thing. I thought what I first observed was different because some focused areas showed the doubling. Another possible reason I had not considered was temperature changes. I too the lens from an air-conditioned house to a very hot outdoors. I have read that mirrors should be allowed time to acclimate.

The ladybug picture was cropped significantly, so the blue flowers were more centered. After this recent shoot with the lens, I will be keeping it. I was impressed with the colors.


PostPosted: Tue Oct 30, 2018 10:59 pm    Post subject: Reply with quote
Hey Michael can you prep me for cleaning my just acquired 600mm? It's got a strange ring around the perimeter of the mirror.



Acquisition was kind of by mistake. I had this and a 400mm f5.6 in my watch list. I was watching tv, then checked my watch list and "jeez thats the mirror I wanted throw in a bid" so I did, only to realise as "you have won this " popped up that it wasn't the 400mm which was what I was really after but this 600mm (I did bid on the 400mm but not as high as I would have done, and was outsniped).
600mm looked good on arrival but pics today are mostly disappointing. This pp'ed cormorant was about as good as I could do.



And this long range shot of the castle shows the terrible contrast.



I need to try without the filter, but I suspect the blemish on the mirror is having an effect. Is it pretty straight forward to open up the rear end?


PostPosted: Sat Jul 03, 2021 9:02 pm    Post subject: Reply with quote
minolta 7000 + minolta 28-135 and sigma mirror telephoto 600 lens. £150.

It's been for sale for a long time, already down from £200. I've got two 7000's, the zoom isn't of great interest. But I like my mirror lenses.
Is it worth throwing a cheeky bid of £100 at it? Question


PostPosted: Sat Jul 03, 2021 11:42 pm    Post subject: Reply with quote
The Minolta 28-135 is a nice lens. The Sigma 600mm is hit or miss. The old camera, meh.


PostPosted: Sun Jul 04, 2021 1:33 am    Post subject: Reply with quote
Lloydy wrote:
minolta 7000 + minolta 28-135 and sigma mirror telephoto 600 lens. £150.

It's been for sale for a long time, already down from £200. I've got two 7000's, the zoom isn't of great interest. But I like my mirror lenses.
Is it worth throwing a cheeky bid of £100 at it? Question


https://www.ebay.com/sch/i.html?_nkw=sigma+600mm+mirror+lens


PostPosted: Sun Jul 04, 2021 6:12 am    Post subject: referring tp ZoneV post sept 2018 Reply with quote
As an entirely obvipous conclusion from the Schneider paper referenced by ZoneV in part 1 of this discusssi0on, the quality f a filter depends on perfectly plane parallell surfaves , more so with longer optics.. This is not relevant to my argument above that filters behind the lens need to be included in the design, but reinforces Minoltas recommendation of a particular quality of rear filter for their designs.

probably not detectable at small magnifications, so the many mirror lenses that have been deprived of their rear filters can be used without worrying about wavelength- of- light- scale errors for ordinary decorative snapshots


p.


PostPosted: Mon Jul 05, 2021 1:53 pm    Post subject: Reply with quote
    Just my 2c. I have several mirror lenses where the manual specifically says that the rear filter IS part of the optical path and therefore should be left in place (or another filter) The filter may affect the pictures or not, but looks like the manufacturers think so and to the extent that they mention it.
    I have 3 different versions of the 600 sigma. One is ok. (mat grey with 95mm filter) One is so-so (army green 86mm filter) but the last one has a story (shiny black 86mm) the lens was rather good, but after a freak mishap it renders now almost like the double pics we're talking about. The lens got under strong pressure from one side, (please don't ask how..🤭🙈.) to the extend that the hood got slightly bent (hood was reversed on the lens by then) . Afterwards the pics got bad and looking like these double focus pics. I assume something also bent inside the lens even though one cannot see any damage. I'm pretty sure cooltouch's lens is damaged. The pics of my other sigmas are much better than his. Maybe something similar happened to his lens. Let me add that my tamron 500 and nikkor-C are both better than the sigmas.


PostPosted: Mon Jul 05, 2021 3:20 pm    Post subject: Reply with quote
Phalbert wrote:
    Just my 2c. I have several mirror lenses where the manual specifically says that the rear filter IS part of the optical path and therefore should be left in place (or another filter) The filter may affect the pictures or not, but looks like the manufacturers think so and to the extent that they mention it.
    I have 3 different versions of the 600 sigma. One is ok. (mat grey with 95mm filter) One is so-so (army green 86mm filter) but the last one has a story (shiny black 86mm) the lens was rather good, but after a freak mishap it renders now almost like the double pics we're talking about. The lens got under strong pressure from one side, (please don't ask how..🤭🙈.) to the extend that the hood got slightly bent (hood was reversed on the lens by then) . Afterwards the pics got bad and looking like these double focus pics. I assume something also bent inside the lens even though one cannot see any damage. I'm pretty sure cooltouch's lens is damaged. The pics of my other sigmas are much better than his. Maybe something similar happened to his lens. Let me add that my tamron 500 and nikkor-C are both better than the sigmas.


Unfortunately, your experience is all too common. Aside from the incident not to be asked about, there is too much variance in sharpness. Many people without experience with mirror lenses might think they have a good one when actually not. A photo-friend recently bought his third or fourth Sig-600 and finally got a sharp one. He was obviously committed to if not obsessed with finding one. As a mirror lens enthusiast, I have often been tempted to try again (have one bad one now) but have resisted. I have a Hartblei (Rubinar 8/500) which is closer to 600mm than 500, as marked. I doubt the Sig-600 would do any better.

I don't mess with the filters other than occasional cleaning, which is quite necessary. I've found that a dusty filter makes a big difference. I do think mirror lenses have a strange relationship with ordinary glass. I was testing a friend's Mirrotar from my lazy seat inside - focusing hrough a window on a tree branch outside and thought the lens had astigmatism. We stepped outside and the focus became as it should.


PostPosted: Mon Jul 05, 2021 4:39 pm    Post subject: Reply with quote
woodrim wrote:
Phalbert wrote:
    Just my 2c. I have several mirror lenses where the manual specifically says that the rear filter IS part of the optical path and therefore should be left in place (or another filter) The filter may affect the pictures or not, but looks like the manufacturers think so and to the extent that they mention it.
    I have 3 different versions of the 600 sigma. One is ok. (mat grey with 95mm filter) One is so-so (army green 86mm filter) but the last one has a story (shiny black 86mm) the lens was rather good, but after a freak mishap it renders now almost like the double pics we're talking about. The lens got under strong pressure from one side, (please don't ask how..🤭🙈.) to the extend that the hood got slightly bent (hood was reversed on the lens by then) . Afterwards the pics got bad and looking like these double focus pics. I assume something also bent inside the lens even though one cannot see any damage. I'm pretty sure cooltouch's lens is damaged. The pics of my other sigmas are much better than his. Maybe something similar happened to his lens. Let me add that my tamron 500 and nikkor-C are both better than the sigmas.


Unfortunately, your experience is all too common. Aside from the incident not to be asked about, there is too much variance in sharpness. Many people without experience with mirror lenses might think they have a good one when actually not. A photo-friend recently bought his third or fourth Sig-600 and finally got a sharp one. He was obviously committed to if not obsessed with finding one. As a mirror lens enthusiast, I have often been tempted to try again (have one bad one now) but have resisted. I have a Hartblei (Rubinar 8/500) which is closer to 600mm than 500, as marked. I doubt the Sig-600 would do any better.

I don't mess with the filters other than occasional cleaning, which is quite necessary. I've found that a dusty filter makes a big difference. I do think mirror lenses have a strange relationship with ordinary glass. I was testing a friend's Mirrotar from my lazy seat inside - focusing hrough a window on a tree branch outside and thought the lens had astigmatism. We stepped outside and the focus became as it should.


Interesting! I wonder if the "astigmatism" would have been eliminated if lens were pointed perpendicular to window glass rather than at an angle? If yes, theorizing, a rear glass filter may be more or less necessary according to how far it is from the sensor, or, according to focal length. -- farther, the angles are less, the filter less necessary. Same for longer focal lengths. Of course those factors would combine.


PostPosted: Mon Jul 05, 2021 5:17 pm    Post subject: Reply with quote
visualopsins wrote:

Interesting! I wonder if the "astigmatism" would have been eliminated if lens were pointed perpendicular to window glass rather than at an angle? If yes, theorizing, a rear glass filter may be more or less necessary according to how far it is from the sensor, or, according to focal length. -- farther, the angles are less, the filter less necessary. Same for longer focal lengths. Of course those factors would combine.


You are correct that the focusing attempt through the glass was at an angle. I'm not going to try to figure it out beyond not shooting through glass anymore. As long as my filters are clean, I'll leave them in place - they're easier to clean than the rear element. I do like the rear filters that slide out for easy cleaning.
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