Pentax 35mm f/4 Takumar on Adorama

[Bill De Jager]

Lens is in E- condition.

 

https://www.adorama.com/us%20%20%201072434.html

[ulf]

I had very a very bad experience when buying a Canon FD 15mm, full frame fisheye lens on eBay from Adorama ca 2001 or 2002.

The lens was classified as E condition.

There was mould on every internal lens surface and on the internal filters.

It should have been classified as G condition.

If I remember correctly I spent totally more than $450 including sale price, shipment, customs-fees and VAT.

 

This was before the eBay purchaser protection program.

Adorama never responded when I tried to reach them.

I tried several eBay messages and I could not reach any responsible person via phone to discuss the problem.

In the end the Adorama identity used in the sale disappeared from eBay too. Banned?

 

Adorama might be better today, but I will never ever buy anything else from them.

[Andrea B.]

Well, I don't blame you for no longer using Adorama, Ulf. That is a bad experience you had for sure!

 

My understanding is that Adorama has improved quite a lot in recent years. I haven't had any problems in the last 5-7 years or so with used lenses or new purchases. There have not been very many Adorama purchases because I almost always go to B&H or KEH both of which I feel are quite reputable and also very fair in their grading assessment of used gear.

 

The Pentax 35/4.0 is a nice lens and should make someone happy for $169.00. It's good with UV (not much below 350) and would work well on a Lumix, Sony or Oly body with an adapter to bring it up to a 45.46mm FFD. I think I paid more than that for my copy. Although I bought it from England at a time when the Euro/dollar rate was a bit against me.

[ulf]

Well, I don't blame you for no longer using Adorama, Ulf. That is a bad experience you had for sure!

In the end I got some practical experience from it.

 

I leaned to identify mould/fungus in lenses and how the lenses surfaces looks on when it has been cleaned away.

 

I was able to open up the lens to reach all internal glass surfaces and clean away all the fungus. In this lens it had only eaten the AR-coatings in some areas, not etched into the glass.

After putting the lens together again it worked rather well and was quite sharp. There must have been some slight loss of contrast due to the missing coatings, but not much.

 

I still have the at lens, but cannot use it due to the different back flange distance between EOS and manual focus Canon cameras (44mm, 42mm)

[Andrea B.]

Speculation: Can missing contrast in a lens be restored using a polarizer turned just a very small amount?

 

Another question for you Ulf: When opening up a lens to clean/lube or repair it, must the elements be replaced in exactly the same position? That is to say, not rotated either way from their original placement? I have heard that this is important, but I'm not sure I agree. I cleaned an EL-Nikkor 80 and it seems to be the same as before even though I know I did not re-seat the elements at precisely the same rotation. I'm not even sure how one could do that unless some marks were placed inside the barrel and on the edge of an element so that the element could be precisely matched up to its original position. But shouldn't optical elements have been created (ground/polished) in such an even way that a rotation consideration is not necessary?

 

Thanks for any input on this element replacement question.

[Andy Perrin]

Andrea, not sure about the contrast, but don't you lose half your light that way?

--

 

I had an experience with an SLR Magic 50mm F/1.1 lens that I bought through eBay from Adorama. The lens was badly misaligned (one side of the image was very blurry). Anyway, they took it back no problem and returned my money. I actually forgot to send them the lens cap back and told them when I realized, but they didn't even ask me to send it back separately (although I offered). This was last year (2018, for the temporally challenged).

[Andrea B.]

That sounds like a lens element was not perpendicular to the main axis?

 

And yes you'd probably lose some light. Can polarizers be untinted?

[Andy Perrin]

Yes to the SLR Magic lens question. I think that’s what it was.

 

Polarizers remove half the light by definition if they are working ideally. Light has an up-down polarization (electric field vibrates vertically) and a sideways polarization (electric field vibrates horizontally). Polarizers that are oriented horizontally for example only let the horizontal part of the field through. So half the light gets thrown away in this ideal situation. Actual polarizers might throw away more due to reflection losses and so on.

 

Wiki has a cool demo with rubber band!

https://en.m.wikiped...rization_(waves)

[Andrea B.]

That is so cool !!

 

On a side note: Wikipedia is getting rather technical these days. They need a Polarization for Dummies write-up.

[ulf]

Speculation: Can missing contrast in a lens be restored using a polarizer turned just a very small amount?

 

Another question for you Ulf: When opening up a lens to clean/lube or repair it, must the elements be replaced in exactly the same position? That is to say, not rotated either way from their original placement? I have heard that this is important, but I'm not sure I agree. I cleaned an EL-Nikkor 80 and it seems to be the same as before even though I know I did not re-seat the elements at precisely the same rotation. I'm not even sure how one could do that unless some marks were placed inside the barrel and on the edge of an element so that the element could be precisely matched up to its original position. But shouldn't optical elements have been created (ground/polished) in such an even way that a rotation consideration is not necessary?

 

Thanks for any input on this element replacement question.

 

I can only guess about this as I do not have any real facts or experience with this.

Almost all lense-elements are rotationally symmetric in design and are likely mounted without a dedicated rotational position.

There could be some very special lenses where the performance is tuned during production by rotating some element(s) when mounted.

This is a complex and expensive way of building lenses and used only as the last resort.

 

In some cases I know about, optimising a lens-elements position to optimize its optical axis in the lens system has been done, but that was not for camera lenses.

In the early laser optical system used in Philips CD-players (CDM1 optical light pen) the front lens element was manipulated into a preferred position.

It was done to align it to the rest of the system, laser, and detectors. the process was handled by a small robotic system and finally the lenselement was locked with UV-glue.

[enricosavazzi]

About the effect of rotating optical elements, this has been discussed multiple times on Photomacrography.net with respect to high-end microscope objectives (especially Mitutoyo M Plan Apo series). Disassembling these objectives at home to clean up the optical surfaces and reassembling them has always (in the cases discussed on that forum) resulted in a marked worsening of the image quality, to the point that the objectives became unusable. Mitutoyo representatives have refused to realign these objectives, since it would cost as much as making a new objective.

 

There are also documented or suspected cases where a sharp knock on the barrel of these objectives (e.g. dropping on a wood floor) has ruined their factory alignment without leaving permanent external markings on the barrel.

 

Most optical elements have two spheric surfaces. During manufacturing, it is common that the centers of the two spheres are not aligned exactly along the same optical axis. Both transversal and tilt decentering is possible. I remember reading that Coastalopt uses custom metal rings when assembling and centering their 60 mm Apo multispectral lens to compensate for transversal decentering of elements, but they do not align to correct tilt decentering because it would be too complex.

 

Edit - A further opportunity for decentering is when an optical element is finished by grinding its periphery to achieve the required diameter.

[Andrea B.]

Thanks everyone for their answers to my question about rotational symmetry. :)

 

I have a lens which I would like to open in order to look at a hazy element. I don't know if the haze is caused by oxidation or something else. So I started thinking about rotational symmetry and wondered if I could ruin a lens when replacing any removeable elements if I did not match the original rotation. I'm happy to learn that the answer is "quite probably not". But I will stay away from microscope objective deconstruction!

 

I've opened up very simple lenses in the past with no ill effects. Example: my EL-80/5.6 which needed a good cleaning.

 

Folks might recall my adventure with the Gamma Tetragon 35?? The Gamma needed cleaning but I one element back into the barrel up-side down. This gave quite a wonderful aura to the subjects of my photos. Sort of a Lens Baby "whoosh" from periphery to center.

[enricosavazzi]

Folks might recall my adventure with the Gamma Tetragon 35?? The Gamma needed cleaning but I one element back into the barrel up-side down. This gave quite a wonderful aura to the subjects of my photos. Sort of a Lens Baby "whoosh" from periphery to center.

If you google "swirl bokeh" you will get examples of similar results. Reversing one element of a legacy lens (especially some Russian-made models) is a time-honored way to enhance this effect. There are instructions on how to do this with some lenses, and sometimes it is even possible to buy spacer rings that make it possible to reverse a critical element and still hold the reversed element away from direct contact with adjacent one(s).

 

I believe the result is a massive increase in spherical aberration, which in some cases produces the desired bokeh without altering too much the image resolution of in-focus parts of the subject.

[dabateman]

Yes this is basically what I did with a M12 lens. I shifted the internal spacers and flipped the rear element. It allowed for near infinity focus, and the center is infocus, while the edges blur out.

 

If you only have 3 elements, the combinations and permutations are not too many. Just play around with a cheap lens and see what you can get. Then people seem to write posts on PetaPixel to make it sound like a new idea.

[Andrea B.]

Enrico: Reversing one element of a legacy lens (especially some Russian-made models) is a time-honored way to enhance this effect.

 

David: Then people seem to write posts on PetaPixel to make it sound like a new idea.

 

I actually did not know that this trick of flipping the element was commonly done!!! :D :D :D

It does make the assessment of the lens sharpness a bit difficult. :lol: