Sigma 600 mirror

cooltouch · Joined: 15 Jan 2009 Posts: 9097 Location: Houston, Texas

Over at the Tamron 55BB thread I began recently I posted an image of the moon I shot a few days ago with my Sigma 600, showing the sort of results I was getting with it. Not good. Well, today, I remembered a routine I don't often use in my processing software, and I was amazed by the amount it cleaned up the image. So even though the original image was very soft, the detail was still there. It just had to be brought out. So here's an example of before and after. The "Before" shot was with no image processing, except reduction to be shown here, and the "After" image is one that I've put through a series of PP steps. I think the difference between the two is remarkable. But I still wish my Sigma was naturally as good as the ones that some of you guys have.

Before:

After:

By the way, over in the Tamron 55BB thread, WNG555 posted a link to a site that shows how to check the collimation of a mirror scope or lens. This is the site:

http://www.mira.org/ascc/pages/lectures/collim.htm

I used it with my Sigma 600, and it isn't as easy as they make it out to be. But at first it looked as if the lens was indeed out of collimation, so I dismantled it to see if there were any obvious adjustments at all. There weren't any. I didn't remove the rings holding the elements in place because it's been my experience that an element sits in its receptacle in one position only and there is no adjustment possible. So for this reason, I didn't loosen or remove any glass. So anyway, I put it back together and checked the collimation a little more closely, under a little better light, and this time, everything lined up the way it's supposed to. So if my Sigma is out of collimation, it is by a very, very small amount. So whatever the problem is with it, it isn't collimation. The glass is spotless. No haze, fungus, dust or anything else. So maybe it's something like the original uncorrected optics on the Hubble Space Telescope. Remember that? It was nearsighted, or something similar because of a mistake in the way the mirror was ground, and NASA ended up having to send up a crew to install a set of corrective lenses so that it could "see" normally. I wonder if something similar may be going on with this lens. Perhaps the mirror was ground just a bit off. Possible, I suppose. A good mirror is ground to within angstroms of being the correct shape.

WNG555 · Joined: 18 Dec 2014 Posts: 784 Location: Arrid-Zone-A, USA

Dramatic before and after...nice job pulling out so much detail.

Too bad that link wasn't more helpful.

CuriousOne · Joined: 31 Dec 2013 Posts: 669 Location: Home

I've talked to a senior lens maker about such problems with mirror lenses. He said, most likely this is mirror defect - wear of device spares used to make mirror, so it's shape not properly parabolic. He said, by introducing a large compensating optical element in front of mirror will correct the problem, but it will be heavy and cost will diminish all usability of mirror lens. So, speaking shortly - you can't do anything. Let's see how my sigma lottery will work out Smile

cooltouch · Joined: 15 Jan 2009 Posts: 9097 Location: Houston, Texas

CuriousOne, your mirror lens expert pretty much confirmed what I already thought. Wear on the machines used to make the optics. If they no longer hold tight tolerances, then they will produce inferior products unless watched very closely. Thus some lenses are great and some are not -- from the same time period of manufacture.

cooltouch · Joined: 15 Jan 2009 Posts: 9097 Location: Houston, Texas

CuriousOne · Joined: 31 Dec 2013 Posts: 669 Location: Home

My Sigma was stopped by customs Very Happy

Seller does not included invoice, and my ebay invoice was not accepted, since it can't be an evidence, so I need to get bank report that I actually paid $51 for it Smile

WNG555 · Joined: 18 Dec 2014 Posts: 784 Location: Arrid-Zone-A, USA

Customs...don't you just love them...must take their pound of flesh from everyone.

CuriousOne · Joined: 31 Dec 2013 Posts: 669 Location: Home

The battle continues, they said that OK, I've paid $51, but lens will be sent to "expertise" to determine, whenever it was really used, as seller described, or we were just altered description to avoid taxes.

cooltouch · Joined: 15 Jan 2009 Posts: 9097 Location: Houston, Texas

Geez, what do those clowns think they have? A solid gold lens or something? The price for a Sigma 600 is easy enough to determine and all the $51 represents is he got it for a good deal!

tb_a · Expire: 2019-08-28

Maybe they should learn from Austrian customs. If something is unclear you have to tell them the *bay number of the item even by phone and they look it up themselves to check the real selling price. For used items in such a low category they wouldn't care at all. It's not even taxable when below 150 Euro (if I recall it rightly). To buy goods the U.S. are far better but obviously for imports we have less problems here. Wink

CuriousOne · Joined: 31 Dec 2013 Posts: 669 Location: Home

Yes but they say that ebay listing is not telling complete story. Who knows, how much you have sent via paypal or via other payment methods? And since their suspictions are only suspictions and are not in court hearing, they can't ask bank, paypal or whatsoever, to give them complete story of your transfers...

Deadline is 15th july. If they will not make any decision up to that day, I can sue them for unnecesarily delaying my parcel and hurting my business, emotional and other sides Smile

tb_a · Expire: 2019-08-28

WNG555 · Joined: 18 Dec 2014 Posts: 784 Location: Arrid-Zone-A, USA

Simply incredible, we are definitely living in insane times.
Rolling Eyes

CuriousOne · Joined: 31 Dec 2013 Posts: 669 Location: Home

There's a small flea market near the customs office. I rarely visit it, since it mostly focuses on porcelain, awards, etc. But, just for curiosity, I went to check it, and I was rewarded - got Jupiter-3 in contax RF mount along with "Kiev" camera for a good price Smile

The lens is already for sale on ebay.

CuriousOne · Joined: 31 Dec 2013 Posts: 669 Location: Home

Got this lens finally!

The mount is quite easy to convert - the rear FD mount assembly is connected to main body via 3 screws, unscrew them, remove mount and you get flush mounting surface, install whatever you want. I will adapt it to M42, for better sales if needed.

Regarding the quality, did only couple of handheld shots so far, but contrast and sharpness is much better than say 500/8 mirror Vivitar lens.

CuriousOne · Joined: 31 Dec 2013 Posts: 669 Location: Home

Got it converted, here are first observations:

1. While focusing barrel rotates much more than say Rokinon's, most action goes in same narrow area as other mirror lens, so focusing is still very difficult.

2. This lens has excellent IQ, way better than cheap Vivitars, MTO's and Rubinars.

3. Focusing is VERY hard. Even when used with peaking, af confirm and so on, movement of lens focusing barrel by 0.1mm changes focused distance by nearly 1 meter, even on objects 200 meters away!

Due to absence of the moon, had to use neighbour's windows blinds as resolution test target. Below is 100% center crop, taken using Sony SLT-A77Mk2, ISO 800, 13 second exposure. I was not able to focus with such sharpness again.

Image is at default settings, no post processing. Check the vertical lines, how sharp they are, despite being shot thru double walled window!

cooltouch · Joined: 15 Jan 2009 Posts: 9097 Location: Houston, Texas

Well, it isn't the best subject to evaluate that lens, but there are aspects of it that would suggest good sharpness. We will look forward to more posts from you and this lens in the future.

WNG555 · Joined: 18 Dec 2014 Posts: 784 Location: Arrid-Zone-A, USA

Looks like you got a very good model. Will be looking forward to your Moon shots.

CuriousOne · Joined: 31 Dec 2013 Posts: 669 Location: Home

Yes, this lens seems to have one of the best sharpness in mirror lens I've ever seen (#1 was Minolta 500/8 AF).

Overcast morning, center crop, no pp:

Same morning, right edge crop, auto levels & sharpen +1:

So this is great lens, but I need longer one, so I will sell this one, and will search for 800mm or better.

CuriousOne · Joined: 31 Dec 2013 Posts: 669 Location: Home

Found a solution how to make focusing easier - I've shortened flange distance as much as possible, so "infinity" was shifted and now lies in "macro" area, making focusing easier. It does not helps very noticeable on DSLR, but still better, than without modification. However, on NEX, when used with "slim" M42 adapter, focusing is much easier.

Here's how mount looks now. This is the preliminary "design", silver colored plate will be machined again, I was not curious enough and can't imagine even that Sigma engineers might drill holes not at 120 degree angles Very Happy

P.S. This lens is for sale, so if anyone wants it and also would like to have custom text on that plate - it's time to PM me Smile

(Text will be in black color, what you see now is just cutout, without paint applied)

WNG555 · Joined: 18 Dec 2014 Posts: 784 Location: Arrid-Zone-A, USA

Very good indeed! The car's rear is quite detailed.

CuriousOne · Joined: 31 Dec 2013 Posts: 669 Location: Home

Not moon, a brick wall, but if anyone interested in RAW output with this lens, here's an example:

http://www39.zippyshare.com/v/etnpbJ75/file.html

CuriousOne · Joined: 31 Dec 2013 Posts: 669 Location: Home

Here you can see micro focus adjustment gear for this lens. The construction is just proof of concept, final will be made in different way, from different materials and also will include fluid dampener for ultra-smooth focusing.

I think I will post this gear for sale separately - it is very easy to fit it on your lens, you need to remove two screws and tighten 3 new ones. No changes made to lens and operation is fully reversible.

WNG555 · Joined: 18 Dec 2014 Posts: 784 Location: Arrid-Zone-A, USA

Ingenious! Reminds me of lenses made for video rigs.

This should cut down on user-induced vibration while focusing. This is a major problem using these mirror lenses....image oscillating hampering one's ability to see the subject in focus or not.

CuriousOne · Joined: 31 Dec 2013 Posts: 669 Location: Home

Thanks!

This system introduces 1:2.5 reduction to focusing mechanism, making focusing easier. Currently I'm thinking about going 2 ways - introduce additional gear, to get say 1:6 reduction and also decrease teeth size for precise adjustment, or just equip it with small dc motor and pistol grip with focusing slider.