[Jaroslav]

I bought recently Vivitar 70-210mm f4.5 K-mount MF lens (one touch design s/n 77* - Kobori made), discussed and well received in the lenses section: https://www.pentaxforums.com/userreviews/vivitar-70-210mm-145-mc-macro-focusing-zoom.html . The tests, straight after the purchase, showed excessive halo effect around white parts of an image at wide open aperture of f4.5. Shining the light though it I saw fungus on many internal surfaces and attributed halo to this fact. Then, using youtube videos and my previous experience, I found gradually access to all surfaces without unmating the helicoids and all surfaces cleaned nicely using cold cream and then propanol and ethanol. But, halo didn't go away . Pity, so much work and for nothing. The halo reduces with f5.6 but image is still not sharp. I know that zooms like this are typically softer wide open, but not to this extent! Using lens hood doesn't help. For comparison, Vivitar 28-200mm f3.5-5.3 (Kobori made) zoom at 200mm wide open at f3.5 is considerably sharper and clearer. Please, see pictures attached: (1) 70-210mm at 210mm and f5.6, (2) 70-210 at 210mm and f4.5, (3) 28-200mm at 200mm and f3.5. Lens elements are shiny clear. Something must be badly wrong.

What could be wrong? Really bad decentering, inadequate blackening of elements sides (look black enough for me), some element(s) are turned around introducing over/under-correction of aberrations or extra internal reflections, other things? I took all precautions that all elements are assembled back in the way they were before opening the lens, but I am not sure that lenses were not opened by someone before me (one screw missing, other one damaged). Cannot find optical design for this lens to check for correct elements sides arrangement.

There are not many combinations for those internal elements that can be reversed, worth trying? Any suggestions for home setup (no collimator, etc.) to check correct assembly?

Would be really grateful for comments.

Attached Images

View Picture EXIF

File Date

 

View Picture EXIF

File Date

 

View Picture EXIF

File Date

 

---

Last edited by Jaroslav; 05-17-2022 at 01:30 PM.

[Bob 256]

Well, I definitely wouldn't have recommended "cold cream". This is an oily substance and can penetrate the coatings on lenses. Getting rid of its residual (if you can) will take a lot of careful cleaning.

What do the three attached images represent? I'm seeing an aperture of f1.0 for each and your lens doesn't give that wide an aperture??

There are some good cleaning recommendations given in this forum and elsewhere, but generally these begin with an air cleaning and then a cleaning with an approved lens cleaner and lens tissue. That's it - no cold cream. If you have fungus, it might be in the cement between the lens elements and no degree of cleaning will reach it there. Surface fungus will come off with the preceding cleaning procedure though a second cleaning with 99%IPA or very pure ethanol might be needed to kill the fungus. Fungus can attack the glass surface and then, again, no degree of cleaning will remove this damage.

[othar]

This lens should be quite usable wide open (I sometimes use it wide open for indoor handball games of my niece), so this is definitely no usual behavior of the lens.
I had a similar problem with a different lens once, after a cleaning attempt of the previous owner, the last lens element was built in reversed, which resulted in strong halos and unsharp images (especially close to infinity focus), maybe something similar happened to your lens.

edit: reversing lens elements by accident happens most likely with very faintly concaved lenses, I would try reversing the last lens element first

[Jaroslav]

Well, I definitely wouldn't have recommended "cold cream". This is an oily substance and can penetrate the coatings on lenses. Getting rid of its residual (if you can) will take a lot of careful cleaning.

What do the three attached images represent? I'm seeing an aperture of f1.0 for each and your lens doesn't give that wide an aperture??

There are some good cleaning recommendations given in this forum and elsewhere, but generally these begin with an air cleaning and then a cleaning with an approved lens cleaner and lens tissue. That's it - no cold cream. If you have fungus, it might be in the cement between the lens elements and no degree of cleaning will reach it there. Surface fungus will come off with the preceding cleaning procedure though a second cleaning with 99%IPA or very pure ethanol might be needed to kill the fungus. Fungus can attack the glass surface and then, again, no degree of cleaning will remove this damage.

Thanks for your reply, Bob256. The photos were taken with Panasonic GX7 m43 camera with PK/m43 adapter, hence no aperture info in exiff. In order of appearance: photo 1: lens in question at f5.6 (moderate halo); photo 2: lens in question at f4.5 (strong halo); photo 3: for comparison other lens, Vivitar 28-200 f3.5-5.3 at f3.5 (no halo, better sharpness).

This is definitely not cleaning issue. All elements are very thoroughly cleaned and checked against the light to be crystal clear. Yes, the final stages required much ethanol, indeed, to get rid of fat residue. No balsam separation was observed. In most cases the coating (seen in reflected light as a blue-purple tin) is preserved completely, in some places fungus had eaten it, leaving dendritic traces in reflected light, but not etched the glass, as no traces are seen for transmitted light. And I've seen several lenses before completely ruined by fungus leaving a dense etching network! I cleaned several lens of dead fungus before, too, which did not etched the glass yet, using available stuff, even just fresh soured cream or Nivea/Florena after shave cream, with very good results, never damaging coating or glass. In some parts of the World, some proper tools are just inaccessible, one uses available means that are available

---------- Post added 05-17-22 at 07:37 PM ----------

This lens should be quite usable wide open (I sometimes use it wide open for indoor handball games of my niece), so this is definitely no usual behavior of the lens.
I had a similar problem with a different lens once, after a cleaning attempt of the previous owner, the last lens element was built in reversed, which resulted in strong halos and unsharp images (especially close to infinity focus), maybe something similar happened to your lens.

edit: reversing lens elements by accident happens most likely with very faintly concaved lenses, I would try reversing the last lens element first

Thanks for your suggestion, othar. Appreciate your experience on wide open performance of a lens! Yes, next will try to reverse the rearmost glass element first, easiest one to try! The other element of a rear group is fixed. Then, a middle group contain only two elements to try swapping their sides. The front group contains middle element that can be reversed only. Not so many combinations. Thanks!

---

Last edited by Jaroslav; 05-17-2022 at 07:29 PM.

[dms]

I don't have the lens, but the performance/halo are not IMO excessive for an inexpensive lens at or near full open. (Or for an older fast expensive lens at/near wide open.) I suggest trying it at f/11. It may be fine there, and if so having two personalities is useful. I would treat it as positive, and use the lens in situation where the look would be desirable (e.g., many colorful lights/portraits/etc. where the softening/fog is attractive).

[othar]

My lens does have a slightly hazy lens element inside (I haven't opened it yet, but I fear an element is separating).
Nevertheless does the lens still deliver in most situations.


Both images are taken at 210mm and f4.5 on my K-3

[Jaroslav]

I don't have the lens, but the performance/halo are not IMO excessive for an inexpensive lens at or near full open. (Or for an older fast expensive lens at/near wide open.) I suggest trying it at f/11. It may be fine there, and if so having two personalities is useful. I would treat it as positive, and use the lens in situation where the look would be desirable (e.g., many colorful lights/portraits/etc. where the softening/fog is attractive).

That's a good option to have at least some use for it. My disappointment is because I have quite good samples of Vivitar 75-200mm f4.5, which is almost as good as SMC-M 75-150mm f4 both wide open, and Vivitar 28-200mm f3.5-5.3. I was expecting similar results from the lens on question. But, alas! In fact, owning all these, I didn't really needed 70-210, just was seduced by a low price. I may keep it or try to sell this for parts then.

---------- Post added 05-18-22 at 02:05 AM ----------

My lens does have a slightly hazy lens element inside (I haven't opened it yet, but I fear an element is separating).
Nevertheless does the lens still deliver in most situations.


Both images are taken at 210mm and f4.5 on my K-3

Othar, many thanks for posting these, it give some reference on how better example of this lense may perform. I guess, I just got some bad example.

---------- Post added 05-18-22 at 02:23 AM ----------

Spent about 4 hours today experimenting with the lens. First thing, I found an optical diagram for it, I put it here:
PSX_20220518_113317.jpg - Google Drive

Then checked correct sides for all glass elements. All were installed correctly. Tried reversing these, just for fun, but at no improvement, the only result was more fuzzy edges and not better central part (that would be interesting to achieve for zoom with pseudo bokeh effect, like monocular lens). Just a bad sample, who knows where it went wrong - glass quality, mechanical tolerances and decentering or other problems...

And yes, as suggested by dms, the lens is usable from f11, but this is a bit limited use, or to use fuzziness as an artistic effect.

I think, I will just give up. It was instructive to learn it's disassembly protocol, etc., perhaps may need this later for better sample. But, for practical use, there are better zooms of similar range and class in my drawer.

[othar]

Too bad you couldn't breathe new life into your specimen.

Thanks for the optical diagram, maybe I'll take a closer look at my hazy lens element in the not too distant future.

[Jaroslav]

Too bad you couldn't breathe new life into your specimen.

Thanks for the optical diagram, maybe I'll take a closer look at my hazy lens element in the not too distant future.

Glad to be of some help with a diagram and good luck with your lens!

[Bob 256]

Thanks for your reply, Bob256. The photos were taken with Panasonic GX7 m43 camera with PK/m43 adapter, hence no aperture info in exiff. In order of appearance: photo 1: lens in question at f5.6 (moderate halo); photo 2: lens in question at f4.5 (strong halo); photo 3: for comparison other lens, Vivitar 28-200 f3.5-5.3 at f3.5 (no halo, better sharpness).

This is definitely not cleaning issue. All elements are very thoroughly cleaned and checked against the light to be crystal clear. Yes, the final stages required much ethanol, indeed, to get rid of fat residue. No balsam separation was observed. In most cases the coating (seen in reflected light as a blue-purple tin) is preserved completely, in some places fungus had eaten it, leaving dendritic traces in reflected light, but not etched the glass, as no traces are seen for transmitted light. And I've seen several lenses before completely ruined by fungus leaving a dense etching network! I cleaned several lens of dead fungus before, too, which did not etched the glass yet, using available stuff, even just fresh soured cream or Nivea/Florena after shave cream, with very good results, never damaging coating or glass. In some parts of the World, some proper tools are just inaccessible, one uses available means that are available

That given along with the additional information just points to a less than optimum performing lens at full aperture (where spherical aberrations abound). The stopped down image isn't that bad. I think your final determination in later posts is correct and this just isn't a great lens compared to other options.

[othar]

That given along with the additional information just points to a less than optimum performing lens at full aperture (where spherical aberrations abound). The stopped down image isn't that bad. I think your final determination in later posts is correct and this just isn't a great lens compared to other options.

I'd rather say it happens to be a bad copy of this lens

[Jaroslav]

Thanks, everybody, really appreciate your replies and hints!