Another budget mirror lens, 900/8 this time

ProfHankD · Jul 29, 2022

Jan Steinman said:
Jan Steinman said:

ProfHankD said:

Got a sample photo or two to try to diagnose it?

Click to expand...

Click to expand...

Some more that I mentioned, starting with the topic lens. My tag says "Samyang," just because someone told me that's what it was. The actual lens has no manufacturer's marking on the barrel!

Doubt it's a Samyang; they'll happily put any brand label on theirs as long as you buy at least 100 or so. Probably a truly no-name lens. I noticed oil smudges on the outside of the lens in some of their advertising shots of it -- not careful behaviour.

Jan Steinman said:
These were all shot outside, since the studio was cramped at these focal lengths. I repeated the OM Zuiko 500/8 x2 for reference and comparison, and it proves itself.

BTW: before your "diagnosis," in all these shots, I set up by first centring the lens on a mirror, then shooting the target. Some of these seem to have significant un-flatness from one side to the other! Which was probably not my setup. Although I guess it could be some flaw in the adapter. I can't state for a fact that these were all shot with the same adapter. (I do have a series of these all shot with the same Metabones Speedbooster Ultra.)

Yes, well, that's pretty sad alright. It does seem oddly consistent across the frame.

The speedbooster often responds very badly to field curvature, but I'm not seeing the variation across the frame that would normally show.

I also don't see any CA. If there's a problem with the non-mirror part, I'd expect some CA, and defocus would also normally show some axial (bokeh) CA.

In short, I can't tell from this what's wrong, but I'm starting to wonder if the mirrors are not front surface. I saw one review that had very clear double images for the things closest to being in focus, and that would be a more clear sign of a non-front-surface mirror... If so, this is just a bad design and nothing will rescue it.

ProfHankD · Jul 29, 2022

3dpan said:
I would like to see something like a 500/5.6 mirror, designed for full frame, with AF, that I could also add a speedbooster to, giving an optional 350/4. But with much improved optics compared with the current crop of mirror lenses.

Well, there is ONE AF mirror lens: the Minolta/Sony 500mm f/8 AF Reflex.

It's actually quite good, and will AF reasonably on modern E/FE bodies using an LA-EA4 or, even better, the Monster modified version of that adapter. It might also work using the LA-EA5, but not on my (older) cameras.

There's no technical reason there couldn't be a speedbooster for it, but not using the above listed adapters. Nobody has made a Minolta AF / Sony A speedbooster with screw-drive AF support.

Jan Steinman · Jul 29, 2022

3dpan said:
I wonder could you post a pic of your "Jintu" 900/8 ?

Mine looks exactly like the top-right one in your photo.

I'm convinced that, either I have a horrible copy, or it could not have taken the photo in the lower right!

3dpan said:
Note what looks like rear surfaced mirrors in the construction,

Yes, that's what the schematic looks like, for both mirrors.

Odd, since my understanding is that Cassagrain reflectors always use front-surface mirrors. That's why they don't have CA. Haven't evaluated this particular one for CA… I'm just so used to thinking, "It's a mirror; it doesn't have CA!"

3dpan said:

--
Jan Steinman

Jan Steinman · Jul 29, 2022

ProfHankD said:
I'm starting to wonder if the mirrors are not front surface.

Did you see Alec's posting with the schematic? It looks like both mirrors are rear-surface!

ProfHankD said:
If so, this is just a bad design and nothing will rescue it.

Totally agree!

It's like, "I wonder what would happen if we combined the worst features of both mirror and refractor designs?"

One thing unique about the Olympus OM Zuiko: generally, the rear mirror has a hole bored through it. In the Olympus design, the rear mirror is simply un-silvered in the centre, and its geometry is part of the optical design.

Like most OM Zuikos, this lens focuses more closely than others of similar design. It actually makes a pretty good portrait lens! And it loves being on a focal reducer.

Olympus E-M1 Mark II, Olympus OM Zuiko 500mm ƒ/8 with Viltrox Mount Adapter EF-M2 II 0.7, for effective 350mm ƒ/5.6. 1/250th, ISO 500, hand-held, from about 10 metres (30 feet).

--
Jan Steinman

Jan Steinman · Jul 29, 2022

3dpan said:
I would like to see something like a 500/5.6 mirror, designed for full frame, with AF, that I could also add a speedbooster to, giving an optional 350/4. But with much improved optics compared with the current crop of mirror lenses.

Keep your eyes peeled for a Sigma XQ 500/4 mirror. It is actually fairly decent, and a focal reducer makes it a 350/2.8. But the fool thing weighs over 3kg.

Olympus E-M1 Mark II, Sigma XQ 500mm ƒ/4, 1/20,000th, ISO 1600.

3dpan said:
Actually, why not even make the mirrors solid glass as per Perkin-Elmer and the Vivitar Series One mirror lenses.

I've not been impressed with images I've seen from the PE-designed "Solid Cat." For one thing, the refracting elements are plastic.

--
Jan Steinman

ProfHankD · Jul 29, 2022

Jan Steinman said:
ProfHankD said:

I'm starting to wonder if the mirrors are not front surface.

Click to expand...

Did you see Alec's posting with the schematic? It looks like both mirrors are rear-surface!

I hadn't seen that schematic. Good catch! If the optical diagram is right, yup, they're rear surface, and that's probably all it took to mess things up this bad. I doubt yours is a "bad copy." I'll take credit for making a really good guess diagnosis. ;-)

Jan Steinman said:
Jan Steinman said:

If so, this is just a bad design and nothing will rescue it.

Click to expand...

Totally agree!

It's like, "I wonder what would happen if we combined the worst features of both mirror and refractor designs?"

This is just plain nuts. They might have been able to make it work with a short focal length, but a 900mm is going to be super touchy about mirror quality.

Jan Steinman said:
One thing unique about the Olympus OM Zuiko: generally, the rear mirror has a hole bored through it. In the Olympus design, the rear mirror is simply un-silvered in the centre, and its geometry is part of the optical design.

Like most OM Zuikos, this lens focuses more closely than others of similar design. It actually makes a pretty good portrait lens! And it loves being on a focal reducer.

Olympus E-M1 Mark II, Olympus OM Zuiko 500mm ƒ/8 with Viltrox Mount Adapter EF-M2 II 0.7, for effective 350mm ƒ/5.6. 1/250th, ISO 500, hand-held, from about 10 metres (30 feet).

Yeah, that looks pretty good.

My Samyang 500mm f/6.3 and Spiratone 300mm f/5.6 are both happy on focal reducers too, but focal reducers vary. Basically, sometimes you get lucky and the focal reducer has aberrations that roughly cancel those of the base lens... sometimes you get very unlucky. However, a good mirror lens shouldn't have lots of CA nor field curvature, and those are the issues that most often mess with focal reducers.

3dpan · Jul 29, 2022

ProfHankD said:
Jan Steinman said:

ProfHankD said:

I'm starting to wonder if the mirrors are not front surface.

Click to expand...

Did you see Alec's posting with the schematic? It looks like both mirrors are rear-surface!

Click to expand...

I hadn't seen that schematic. Good catch! If the optical diagram is right, yup, they're rear surface, and that's probably all it took to mess things up this bad. I doubt yours is a "bad copy." I'll take credit for making a really good guess diagnosis. ;-)

ProfHankD said:

ProfHankD said:

If so, this is just a bad design and nothing will rescue it.

Click to expand...

Totally agree!

It's like, "I wonder what would happen if we combined the worst features of both mirror and refractor designs?"

Click to expand...

This is just plain nuts. They might have been able to make it work with a short focal length, but a 900mm is going to be super touchy about mirror quality.

ProfHankD said:

One thing unique about the Olympus OM Zuiko: generally, the rear mirror has a hole bored through it. In the Olympus design, the rear mirror is simply un-silvered in the centre, and its geometry is part of the optical design.

Like most OM Zuikos, this lens focuses more closely than others of similar design. It actually makes a pretty good portrait lens! And it loves being on a focal reducer.

Olympus E-M1 Mark II, Olympus OM Zuiko 500mm ƒ/8 with Viltrox Mount Adapter EF-M2 II 0.7, for effective 350mm ƒ/5.6. 1/250th, ISO 500, hand-held, from about 10 metres (30 feet).

Click to expand...

Yeah, that looks pretty good.

My Samyang 500mm f/6.3 and Spiratone 300mm f/5.6 are both happy on focal reducers too, but focal reducers vary. Basically, sometimes you get lucky and the focal reducer has aberrations that roughly cancel those of the base lens... sometimes you get very unlucky. However, a good mirror lens shouldn't have lots of CA nor field curvature, and those are the issues that most often mess with focal reducers.

Looking at this diagram of the Oly 500/8 it seems Oly used rear surfaced mirrors too,

https://flic.kr/p/6DuCxA

And this link too, showing the variations in the Vivitar solid cat mirror arrangement, with and without air gaps between mirrors. But no reference to plastic mirrors.
And I think you'll find the only plastic is a flat front protective sheet. No optical feature.

https://flic.kr/p/dvSYAT

PS.
I have the 450/4.5 and the 600/8 Solid Cats by Vivitar.

ProfHankD · Jul 29, 2022

3dpan said:
Looking at this diagram of the Oly 500/8 it seems Oly used rear surfaced mirrors too,

https://flic.kr/p/6DuCxA

Obviously to better effect...

Perhaps it's just a lower-quality mirror and/or coatings in the 900mm f/8? Then again, longer focal lengths do tend to be touchier.

3dpan said:
And this link too, showing the variations in the Vivitar solid cat mirror arrangement, with and without air gaps between mirrors. But no reference to plastic mirrors.
And I think you'll find the only plastic is a flat front protective sheet. No optical feature.

https://flic.kr/p/dvSYAT

PS.
I have the 450/4.5 and the 600/8 Solid Cats by Vivitar.

Wow! Those are hard to come by and not cheap.

3dpan · Jul 29, 2022

ProfHankD said:
3dpan said:

Looking at this diagram of the Oly 500/8 it seems Oly used rear surfaced mirrors too,

https://flic.kr/p/6DuCxA

Click to expand...

Obviously to better effect...

Perhaps it's just a lower-quality mirror and/or coatings in the 900mm f/8? Then again, longer focal lengths do tend to be touchier.

ProfHankD said:

And this link too, showing the variations in the Vivitar solid cat mirror arrangement, with and without air gaps between mirrors. But no reference to plastic mirrors.
And I think you'll find the only plastic is a flat front protective sheet. No optical feature.

https://flic.kr/p/dvSYAT

PS.
I have the 450/4.5 and the 600/8 Solid Cats by Vivitar.

Click to expand...

Wow! Those are hard to come by and not cheap.

The 450/4.5 does not seem to be anything special optically, but it looks a masterpiece of manufacturing excellence.

My 600/8 is a bit neglected and not looking quite so impressive.

3dpan · Jul 30, 2022

Jan Steinman said:
3dpan said:

I wonder could you post a pic of your "Jintu" 900/8 ?

Click to expand...

Mine looks exactly like the top-right one in your photo.

I'm convinced that, either I have a horrible copy, or it could not have taken the photo in the lower right!

Jan Steinman said:

Note what looks like rear surfaced mirrors in the construction,

Click to expand...

Yes, that's what the schematic looks like, for both mirrors.

Odd, since my understanding is that Cassagrain reflectors always use front-surface mirrors. That's why they don't have CA. Haven't evaluated this particular one for CA… I'm just so used to thinking, "It's a mirror; it doesn't have CA!"

Jan Steinman said:

Click to expand...

The one with the fluted focus band seems to be more commonly sold as a Dorr Danubia.

It's not actually shown on the Jintu website now.
I don't know if that might imply the version with the square-pattern is later/ improved (hopefully).

3dpan · Jul 30, 2022

Jan Steinman said:
3dpan said:

I would like to see something like a 500/5.6 mirror, designed for full frame, with AF, that I could also add a speedbooster to, giving an optional 350/4. But with much improved optics compared with the current crop of mirror lenses.

Click to expand...

Keep your eyes peeled for a Sigma XQ 500/4 mirror. It is actually fairly decent, and a focal reducer makes it a 350/2.8. But the fool thing weighs over 3kg.

Olympus E-M1 Mark II, Sigma XQ 500mm ƒ/4, 1/20,000th, ISO 1600.

Jan Steinman said:

Actually, why not even make the mirrors solid glass as per Perkin-Elmer and the Vivitar Series One mirror lenses.

Click to expand...

I've not been impressed with images I've seen from the PE-designed "Solid Cat." For one thing, the refracting elements are plastic.

I am actually watching eBay listings for the Sigma 500/4, but they're maybe a bit high for me at this time.
I was a bit put-off by this blog by Jim Chung,

Checking out the Sigma 500 mm f/4 XQ mirror lens

Those of you familiar with this blog will no doubt recognize this troubling fondness I have for vintage camera telephoto mirror lenses. I’m always on the prowl for that inexpensive yet high…

jimchungblog.com

Eggplantt · Jul 30, 2022

Lots of posts, where to start?

Tom Caldwell said:
Surely shorter focal length Mirror Lenses will still give advantage and it is easier to make them somewhat faster if the focal length is not so extreme.

Initial fancy makes one wonder about a f4.0 100mm mirror lens pancake. But of course the shorter focal lengths run into the law of diminishing returns size/weight wise. Then there is the fixed aperture business, especially if it becomes too fast.

So while we pursue the ideal of long and longer the old 250-300 mirror lenses that once were offered seem to have become like hen's teeth. The last time I looked (quite a while ago) the asking price was huge - probably more for rare value than image quality.

But I do have a little Tokina 300/6.3 made for M4/3 mount which is quite cute. I managed to buy it on sale years ago and the price seems to have gone up since then.

Arguably 100mm refracting lenses are little larger than a typical 50mm prime - see the Olympus for example

The equivalent centrally-obstructed Cassegrain mirror lens would have to be larger in diameter.

And I feel the 250-300mm range is easily obtained with a refracting lens + crop sensor camera now. Even cropping from full frame, would you take the lower MP over mirror lens bokeh? I sure would..

Jan Steinman said:
3dpan said:

I would like to see something like a 500/5.6 mirror, designed for full frame, with AF, that I could also add a speedbooster to, giving an optional 350/4. But with much improved optics compared with the current crop of mirror lenses.

Click to expand...

Keep your eyes peeled for a Sigma XQ 500/4 mirror. It is actually fairly decent, and a focal reducer makes it a 350/2.8. But the fool thing weighs over 3kg.

I've not been impressed with images I've seen from the PE-designed "Solid Cat." For one thing, the refracting elements are plastic.

They certainly aren't plastic. Have you felt how heavy they are? ;-)

Not even the Perkin Elmer 680mm has plastic refracting optics. And also, I have a factory reject mirror blank from one of them, which again certainly isn't plastic.

Jan Steinman said:
Note what looks like rear surfaced mirrors in the construction said:

ProfHankD said:

3dpan, post: 66358682, member: 84348"]
PS.
I have the 450/4.5 and the 600/8 Solid Cats by Vivitar.

Click to expand...

Wow! Those are hard to come by and not cheap.

Click to expand...

Click to expand...

Just for the record, the 600/800 Solid Cats seem wildly overpriced on eBay buy it nows- I have seen them regularly go for £150-220 at auction. An odd behaviour when people list them for £600, but one I've seen happen many times.

The 450mm f4.5 really is rare.

Jan Steinman said:

The 450/4.5 does not seem to be anything special optically, but it looks a masterpiece of manufacturing excellence.

My 600/8 is a bit neglected and not looking quite so impressive.

Click to expand...

My mint 800mm f11 is pretty good. If you read all the reviews of them at the time, the tests showed they generally resolved a little less than other mirror lenses. But it is decent contrast and items pop into focus.

The patents are very well documented in books and optical design software, so expected performance is easy to see of this class.

Fwiw- the 450mm f4.5 is not a solid catadioptric. Also, the 600 and 800 are physically identical- only an internal doublet is tweaked to get a longer focal length. The 600 in tests was shown to resolve a bit more.

Eggplantt · Jul 30, 2022

In terms of mirror lens design- I am waiting for someone to combine a telephoto, off-axis tilted component telescope (TCT) design (no donut bokeh) with solid glass lenses to shorten it:

Pictured- Makowsky, off-axis Cassegrain

There are a lot of amateur off-axis designs out there such as the Herrig and Schiefspeigler.

Things like the Chiefspeigler are very impressive but give up being telephoto. The Herrig seems hard to produce/test for an amateur due to it's extremely long focal length mirrors which are reflected off of twice. This would give faint picture in testing equipment. There is still, however, decent discussion out there on what you could do though.

3dpan · Jul 30, 2022

Eggplantt said:
In terms of mirror lens design- I am waiting for someone to combine a telephoto, off-axis tilted component telescope (TCT) design (no donut bokeh) with solid glass lenses to shorten it:

Pictured- Makowsky, off-axis Cassegrain

There are a lot of amateur off-axis designs out there such as the Herrig and Schiefspeigler.

Things like the Chiefspeigler are very impressive but give up being telephoto. The Herrig seems hard to produce/test for an amateur due to it's extremely long focal length mirrors which are reflected off of twice. This would give faint picture in testing equipment. There is still, however, decent discussion out there on what you could do though.

There is a Makowsky-Katoptaron turns up on eBay occasionally, refer,

https://www.keh.com/shop/makowsky-katoptaron-500mm-f-8-ts-500-e-manual-aperture-manual-focus-mirror-lens-with-t-mount-adapter-for-sony-alpha-mount-67.html

Eggplantt · Jul 30, 2022

3dpan said:
Eggplantt said:

In terms of mirror lens design- I am waiting for someone to combine a telephoto, off-axis tilted component telescope (TCT) design (no donut bokeh) with solid glass lenses to shorten it:

Pictured- Makowsky, off-axis Cassegrain

There are a lot of amateur off-axis designs out there such as the Herrig and Schiefspeigler.

Things like the Chiefspeigler are very impressive but give up being telephoto. The Herrig seems hard to produce/test for an amateur due to it's extremely long focal length mirrors which are reflected off of twice. This would give faint picture in testing equipment. There is still, however, decent discussion out there on what you could do though.

Click to expand...

There is a Makowsky-Katoptaron turns up on eBay occasionally, refer,

https://www.keh.com/shop/makowsky-k...-t-mount-adapter-for-sony-alpha-mount-67.html

I've had an eBay saved search for this for ages- nothing has ever come up :-( :-( :-( :-(

I would happily trade my Vivitar 800mm f11 for it, amongst other things..

EDIT: How did I miss out?? More hits for Goema Katoptar...

Katoptar TS 500 E Goema 1:8 500mm Germany Objektiv Olympus OM Anschluss | eBay

GOEMA KATOPTAR TS 500 E, nur-Spiegel-Objektiv, 1:8 / 500mm, sehr selten! EUR 450,00 - PicClick DE

GOEMA KATOPTAR TS 500 E, nur-Spiegel-Objektiv, 1:8 / 500mm, sehr selten! EUR 250,00 - PicClick DE

My search was for (katoptaron, telespect, katoptar, goema, makowsky)... seems like these sale pages are awhile ago though.

3dpan · Jul 30, 2022

Eggplantt said:
3dpan said:

Eggplantt said:

In terms of mirror lens design- I am waiting for someone to combine a telephoto, off-axis tilted component telescope (TCT) design (no donut bokeh) with solid glass lenses to shorten it:

Pictured- Makowsky, off-axis Cassegrain

There are a lot of amateur off-axis designs out there such as the Herrig and Schiefspeigler.

Things like the Chiefspeigler are very impressive but give up being telephoto. The Herrig seems hard to produce/test for an amateur due to it's extremely long focal length mirrors which are reflected off of twice. This would give faint picture in testing equipment. There is still, however, decent discussion out there on what you could do though.

Click to expand...

There is a Makowsky-Katoptaron turns up on eBay occasionally, refer,

https://www.keh.com/shop/makowsky-k...-t-mount-adapter-for-sony-alpha-mount-67.html

Click to expand...

I've had an eBay saved search for this for ages- nothing has ever come up :-( :-( :-( :-(

I would happily trade my Vivitar 800mm f11 for it, amongst other things..

EDIT: How did I miss out?? More hits for Goema Katoptar...

Katoptar TS 500 E Goema 1:8 500mm Germany Objektiv Olympus OM Anschluss | eBay

GOEMA KATOPTAR TS 500 E, nur-Spiegel-Objektiv, 1:8 / 500mm, sehr selten! EUR 450,00 - PicClick DE

GOEMA KATOPTAR TS 500 E, nur-Spiegel-Objektiv, 1:8 / 500mm, sehr selten! EUR 250,00 - PicClick DE

My search was for (katoptaron, telespect, katoptar, goema, makowsky)... seems like these sale pages are awhile ago though.

I have seen the M-K advertised more than once on eBay, but that was probably at least 2-3 years ago, and it may have been the same one re-advertised.

Jan Steinman · Jul 30, 2022

3dpan said:
Jan Steinman said:

Keep your eyes peeled for a Sigma XQ 500/4 mirror.

Click to expand...

I was a bit put-off by this blog by Jim Chung,

https://jimchungblog.com/2018/01/28/checking-out-the-sigma-500-mm-f-4-xq-mirror-lens/

Yea, I saw that, too.

Luckily, mine has no hazing or fungus. The comments imply design flaws. Perhaps I got a "good" sample variation for a change!

The markings on the case implies that it was owned by the Bonneville Power Administration's High Voltage lab. I envision engineers looking at huge insulators, high up on a utility tower. Perhaps they took better care of it than the "hazy" lens owners did.

3dpan · Jul 30, 2022

Jan Steinman said:
3dpan said:

Jan Steinman said:

Keep your eyes peeled for a Sigma XQ 500/4 mirror.

Click to expand...

I was a bit put-off by this blog by Jim Chung,

https://jimchungblog.com/2018/01/28/checking-out-the-sigma-500-mm-f-4-xq-mirror-lens/

Click to expand...

Yea, I saw that, too.

Luckily, mine has no hazing or fungus. The comments imply design flaws. Perhaps I got a "good" sample variation for a change!

The markings on the case implies that it was owned by the Bonneville Power Administration's High Voltage lab. I envision engineers looking at huge insulators, high up on a utility tower. Perhaps they took better care of it than the "hazy" lens owners did.

Yeah, I'm ever optimistic.

There are two on eBay at present, one from Italy and one from Germany. Approx $1600NZ and $2600NZ respectively, + shipping.

ProfHankD · Jul 30, 2022

3dpan said:
3dpan wrote:
I don't know if that might imply the version with the square-pattern is later/ improved (hopefully).

It's literally a different rubber band -- probably no significance other than they found a cheaper supplier...

Jan Steinman · Jul 30, 2022

3dpan said:
There are two on eBay at present, one from Italy and one from Germany. Approx $1600NZ and $2600NZ respectively, + shipping.

Ouch! I paid US$220 for mine, also on evilBay.

I think it was so cheap because of poor photographs in the description. Obvious camera-mounted flash showed up every tiny flaw, and made the glass look frosted. It looked like crap, but I was willing to risk ~$250 or so on it. It turned out to be in much better shape than the photographs indicated. Luck over skill!

It always surprised me that people selling lenses seldom know how to photograph them properly! Must be the equipments' fault…

I don't know what alternatives to eBay are available to you in NZ, but I'm presently somewhat soured on evilBay. I'm finding I get more consistent quality and value from well-established used camera stores.

Another budget mirror lens, 900/8 this time

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