Hasselblad-Proxars, or Extension tubes?

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Ed Sukach

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My word... What a hornet's nest I've stepped into here.

The 'difference' between refraction and reflection is ... drum beat ... the CRITCAL angle!!! If anyone doesn't understand this ... a study of Snell's law is in order. (BTW - I was NOT disagreeing with your statement).

I will make my statement again: An optical system (lens, if you will), CAN be improved by the addition of a supplementary lens. Perhaps the Hubble was not the best example - but it certainly WAS an example of improvement ... not "perfection", but it was IMPROVED.

I do NOT want this to degrade to a "Win- Lose" argument (if it has not already). I am trying to stay on-track, with what little I know about lens design and production. If anyone chooses to use bellows, extension tubes,`Proxar' supplementary lenses, saran wrap or Mel's Mystery Smoke - that is fine with me.

Now ... backing up a little...

The first step in the design of every camera lens is to define the desired properties. A list of design parameters will be established: Field and format; focal length; maximum and minimum field distance; resolution (MTF, now); acceptable aperture range; size and mechanical considerations - and a HOST of others.

The design is done to satisfy these parameters - and for ALL intents and purposes, the lens manufacturers DO. The Zeiss design crew certainly DOES - it will be rare day in a frozen hell when they slip so far as to condone a whole line of supplementary lenses, such as Proxars, and not know what effect their use has on the performance of their lenses.

We are discussing the use of lenses beyond their original design parameters - through the use of either supplementary lenses, OR extension tubes / bellows. Supplementary lenses "change" focal length to something other than required in the original design specifications; tubes situate the lens further from the film plane than originally intended. In either case, the performance of the lens is affected.

That effect will be difficult - in my book, too difficult to be of ANY value - to determine without a critical analysis of the lens design: it certainly cannot be left to a blanket, "All close up lenses WRECK the overall optical system - lens or mirror ... or whatever ... performance".

This might be of interest - from Lens Testing 101: In examining a lens for resoultion on an optical bench, what media is used as a focal plane?

BTW - Introducing another element to convert a single element to a cemented (n.b. "cemented - together) pair WILL reduce the amount of light transimitted - with *no* additional relfective surfaces - see "T" stops.
 

Ed Sukach

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Another good illustration is someone with perfect eyesight putting on the eyeglasses made for someone who has everything wrong with his eyesight that could possibly be wrong.
In other words: your illustration sucks. :D

Or vice versa, in which case it doesn't suck.

It only works if you assume that the lens you are using has a defect. And not only a defect, but one that can be remedied using a simple positive lens.

By "defect" do you mean ANY deviation from perfection? If so, ALL lenses are "defective". But that has nothing to do with the use of Proxars. In my mind the question is about their acceptable use - and that acceptability is squarely in the perception of the photographer.

So to make sense of it, we are to assume that Zeiss' designers are very bad at what they do, except the ones who made the Proxars.
And they are not only good, but so good that they can correct the crappy lenses their colleagues made using a simple positive lens put in front of all of them.

Weird logic. No, we are NOT to assume anything - I've stated, repeatedly, my admiration for Zeiss and their design engineers.
 

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I have not used the proxars but I have a great deal of experience with close up or macro work including the use of extension tubes. If you're talking about a head and shoulders portrait, or even a tight face shot, an extension tube is a reasonable way to get high quality results. However if you want the best optical performance possible for that reproduction ratio or especially even greater magnification, then you should use a macro lens. However the detail and resolution of a macro lens can be brutal when used for a portrait. For close up still life a macro lens is by far the best solution.
 

Q.G.

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Or vice versa, in which case it doesn't suck.
Oh, it sucks all right.
Proxars do not (!) improve image quality, only because an auxillary lens put in front of the defective Hubble does.


By "defect" do you mean ANY deviation from perfection? If so, ALL lenses are "defective". But that has nothing to do with the use of Proxars. [...]
That's right.
And that is because you are changing the subject.
:D

Weird logic. No, we are NOT to assume anything - I've stated, repeatedly, my admiration for Zeiss and their design engineers.
Isn't it ("weird logic") indeed?
You think that Proxars do not have a deteriorating effect on Zeiss lenses, because you admire the designers of these Zeiss lenses for having done their best to make them the best they can be, without these cheap, simple crappy pieces of glass in front of them?

The 'bottom line' is that putting one of these single element bits of glass with curved sides in front of a good lens may be considered for reasons of economy, or laziness, but is not a good idea.
Proxars introduce all (!) possible lens aberrations (the ones those revered Zeiss designers painstakingly 'designed away'), reducing your expensive lenses to the level of some less expensive ones.
So if you think it a good idea to use these thingies still, you might also want to remind yourself why you spent the amounts you have on getting good lenses to begin with, and ask yourself which of the two decisions - use Proxars, or spend enough to get good lenses - was the silly one.

Using tubes is less easy, but far better.
 

df cardwell

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Using tubes is less easy, but far better.


Q.B.

Here is how Andrew framed his question:

"...what preference people had for either Proxar filters, or extension tubes? MY main reason for extra close focus potential is for head and shoulder portraits with my 80mm or 150mm, as well as the odd still life."

So, my questions for you are
What are your criteria for successful
head and shoulder portraits ?


What did you gain by using Proxars on these two lenses,
and what were the advantages of using ext. tubes ?

Here's the part of shooting this type of shot that always tripped ME up:

The 150 with the 8mm tube gives you a field width of 2 to 3 feet.
The lens alone has a field width of 3 1/2 feet.

Don't you think it is ironic that most of the pictures you want to take are in between the close-focus limit of the lens, and the far focus limit of the lens with short extension tube ?

How would solve this problem,
without buying a new lens ?

The criteria we choose for success
determine the limitations we accept
when we leave the physics lab and go out to make pictures.

How would YOU take this kind of picture ?

Note: this is not intended as an attack,
merely a gentle nudge to keep us on topic
to try to help answer the author's question.


Thanks.
 
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Andrew Moxom

Andrew Moxom

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I appreciate all the advice, and it appears there is still much debate about which is the right path, and the information is all valid. I think I have what I am looking for, and that's to go with tubes. I feel this thread needs to end now. Thanks for taking the time to post and add to this thread.
 

Q.G.

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[...] Here's the part of shooting this type of shot that always tripped ME up:

The 150 with the 8mm tube gives you a field width of 2 to 3 feet.
The lens alone has a field width of 3 1/2 feet.

Don't you think it is ironic that most of the pictures you want to take are in between the close-focus limit of the lens, and the far focus limit of the lens with short extension tube ?

How would solve this problem,
without buying a new lens ?
Simple.
By not trusting erroneous data. :wink:

The 150 mm lens, unaided, has a minimum field of view of 40 cm (1.3 ft).
Not 3.5 ft.
It has that, because it has 21 mm of extension built-in.

The 150 mm lens with 8 mm tube has a field of view of 107 cm/3.5 ft (maximum) to 29 cm/0.95 ft (minimum).

Lots of overlap with the lens alone, so not a good choice, the 8 mm tube.

The most logical tube to add would be the 21 mm tube, with the lens + tube combination starting where the lens alone stops.

If you can't find the old 21 mm tube, the next best one to use with the 150 mm lens would be the 16 mm. But you then pay for 5 mm overlap, which you of course don't need.

How would YOU take this kind of picture ?
250 mm lens with 32 mm tube.

Edit: make that 80 mm, (110 mm,) 120 mm or 150 mm, all without tube.
All that talk about proxars or tubes made me forget we were talking about head and shoulders. You do not need tubes or Proxars for H&S.


Note: this is not intended as an attack,
merely a gentle nudge to keep us on topic
to try to help answer the author's question.


Thanks.
I don't mind 'attacks'. I do 'attack' myself too.
I hate disinformation, and nonsense, and will not (cannot - it's my faulty personality) leave it unchallenged. :wink:
 
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Ed Sukach

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I appreciate all the advice, and it appears there is still much debate about which is the right path, and the information is all valid. I think I have what I am looking for, and that's to go with tubes. I feel this thread needs to end now. Thanks for taking the time to post and add to this thread.

Andrew, I appreciate your position here, and applaud what appears to be an attempt to pour oil over troubled waters.

There should be no guilt over your involvement in what has, or is in imminent danger of, descending into a flame war, or a series of ad hominem attacks.
As usual, though, there seems to be an unwritten rule that, "He who quits admits the error of his argument by his silence."

I will defend what I have written by means of ... great heavens!!! ... more than 50 years of contact with optics and photography, as an amateur and later professional Photographer, and as formally trained Optical Quality Assurance Specialist ... but I agree, this is not the proper place to continue.

I'll start a new thread, "Proxar Considerations" ... in the "Soap Box", where each of us can present our arguments and hopefully, reach some sort of truth.

Hopefully also, readers will be able to assess the validity of each of our arguments from their content and tone, syntax, and how well they apply to the subject.

What about it, gang... are willing to go to the Soap Box ... or are you going to ADMIT DEFEAT?
 

df cardwell

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Simple.
By not trusting erroneous data. :wink:

YEP, GOOD CATCH ! Thank YOU !

If I had been working on the table saw, the cat would have my fingers !

After some head scratching, I guess the only reason I was tossing out those numbers was that I maybe was thinking about the 250.

SO, finally, I took out the old Hassie book (I kept long after parting with the camera) And even the old focuses to 5 feet, close enough to do the job. Would old photographers focus as clearly !

I know that I get distracted by the adrenaline. Thanks for the sweet reason, and good data.

don
 

Ed Sukach

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In recognition of the sensitivity of some of those who dislike intense discussions, I've posted a couple of replies in the Soap Box. Let's continue this discussion there.

All who are *convinced* that they are the keepers of sacred, undeniable TRUTHS, and photography gurus of the nth degree - so high on the scale that no mere mortals can touch them, are welcome.

Add "Mere Mortal" to my signature.
 
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