+10 to 4 'achromatic' close up diopter from telephoto zoom, in typical filter thread!

[Eggplantt]

The rearmost Miranda 75-300 can't be used this way but is nevertheless removed in the same fashion.

The 58mm Tamron 103A one is facing the 'wrong way' as I don't have the right step rings to hand. Nevertheless, the glass is easily flipped as the retaining ring wasn't obviously glued. Performance has been known to sometimes improve with the 'wrong' orientation of a close-up achro so YMMV. It performs just fine this way.

I'm not a macro photographer and will want to do some more testing, but I haven't seen this specifically easy means of reusing telephoto zoom optical parts discussed.

The idea is to reuse the/part of the front group of a (non-retrofocus) telephoto zoom- 70-200, 70-300, 35-200, 28-200- which on a number of lenses is in a self-contained threaded housing, inserted/removed via the lens' filter thread.

That means they're in standard metric threads like M49x0.75 and can be 'bolted' straight onto any camera lens you desire!

I've found someone reusing part of a telephoto front group as a close-up filter online, but only after chopping the entire front section of the lens off in order to get a usable attachment thread (elements did not have their own adaptable housing).

This is many times easier than that, not withstanding the cost of lens disassembly tools. This is however typically the easiest part to get to (and is the scene of many 'I give up' repairs :-D ).

Benefits

- Achromatic, multicoated (chance of fancy 'fluorine'/stronger coatings?)

- Can end up with special low-dispersion elements which would probably be horrendeously overpriced if sold as dedicated close-up filter

- Huge variation/range of powers, even amongst lenses of the same focal length: shorter = more powerful, etc

- Range of appropriate lenses easy to acquire at little cost

- Great way to recycle a lens, might save something otherwise from the bin

- Far better than cheap and nasty kits

- Likely the best part of a premade lens that can be expected to perform on its own, well (especially from afocal zoom!)

Risks

- Difficult and potentially costly to find out which lenses are constructed this way

• Not necessarily noted in disassembly tutorials online;
• No database, record of which are constructed this way;
• Can't find anything about this online!

- AF zooms not attached this way, in my limited experience, therefore limit to how modern you can go

- Everything to do with removing and reusing only bits from a premade optical scheme, even in afocal zoom:

• Abberations may not be as fully corrected as they could be for a close up lens, as that might be done later in the optical train which is missing
• Part of the front group may be seperate to/missing from the housing, limiting performance; Tamron above is example of this (empty lens filters etc could help here)

 

[Eggplantt]

Tamron 103a 80-210mm f3.8-4

58mm thread

49.4mm glass diameter

About 225mm FL (+4.4D)

19.9mm housing thickness (lens 'inset' in housing)

2 elements, 1 group, multicoated (purples)

Retaining ring not glued

Whole front group not in housing (front plano-convex element loose and removable)

HOYA HMC ZOOM & CLOSE FOCUS 80-200mm 1:5.5
(Many names)

49mm thread

40mm glass diameter

About 100mm FL (+10D)

10.7mm housing thickness (lens not 'inset' at all)

2 elements, ? group, coated (probably multi but difficult to test indoors, partially because of orange/white colour)

Retaining ring glued

Whole front group in housing

 

[Eggplantt]

Application

Attaching the self-contained housing part of the Tamron 103A to my Tamron 28mm f2.5 (42mm FF equiv as used on APS-C), minimum focus reduced from 0.25m to 0.074m, new focus range now 0.074-0.22m

(or 7.4cm-22cm)

This focus range with this wider than normal angle of view proves very useful to small product/item photography- everything on one side of a table.

"So what?" you might think, but with limited indoor lighting I'll take this over requiring a tripod due to the light loss of extension tubes. Many of my lenses are almost handholdable indoors normally at f2.8~, but won't focus close enough sometimes. I'm sure you have the same issue.

Note- this is the tested minimum focus on my Tamron -> EOS + EOS -> E-Mount adapter, which is abit short and allows focusing past infinity. Therefore, expect it on a 'tuned' adapter to focus a fair bit closer. I lack the experience to say by how much, but judging on how far it goes past infinity, it would be meaningful.

All at f2.5, with the aforementioned combination

ISO 640, resting on tape

ISO 100, resting on a pile of stuff

100% crop

This Tamron is the weakest diopter power of the three- including the Miranda 75-300mm front group here- but not by much. Therefore, its reduced pincushion distortion compared to those two is appreciated.

It's not really bothersome/significant on the other two (held up to my eye), using the standard of lens reviews I've read online (ephotozine, phillipreeve).

 

[Eggplantt]

Application

I prepared a comparison image of 'grab n' go' close up solutions (reversing doesn't work here) - extension tubes vs this 'DIY' diopter, HOYA HMC TELE -AUTO F=135MM 1:2.8. Not the close focus one, and is unit-focus lens.

It's always had 'glow'/CA at normal distances anyway. I chose not to add more extension because I was already a stop behind- more a comparison of what you can get out of things.

EDIT: I left the sensor on 16:9, so the photos are 20MP. Sorry.

 

[Tons o Glass]

Nice idea. The front elements are often the focus group - perhaps the Tamron's front should have been kept more intact (as 3 elements in 2 groups)?

Coincidentally I recently did something similar by repurposing an old Meade telescope objective (900mm f/15 - 60mm diameter airspaced doublet with maybe one coated surface if any) with a 3D printed thread adapter. It improves close focus enough to be helpful on 200mm primes while keeping the character of the original lens mostly intact, but it will likely add some vintage characteristics in the contrast and flare departments, and it does affect LoCA a little bit for better or for worse depending on the base lens.

I've thought about doing this type of thing with a Spiratone Plura-coat Sharpshooter (400/6.3) that I have since it's missing the rear group (oops, oh well no wonder it was $5). As a sidenote, the Spiratone in this configuration is more like 300mm and is a bit "dreamy".

 

[WindwardHaole]

You may appreciate Art Vaughan's Flickr photostream for similar applications.

 

[Eggplantt]

Nice idea. The front elements are often the focus group

Yup-it is the focus group we are after, of a telephoto zoom lens, which is the first group of lenses. Even when this is no longer responsible for focusing, as in an internal-focus lens, the front group still remains a strong positive power element by design.

Just to be clear, whilst the retrofocus zoom focuses with the front group, you can't use it as a close-up filter as its negative power- this has the opposite effect, and moves the focus point further away.

A telephoto design- positive, negative

A retrofocus (inverse telephoto) design- negative, positive

An obvious telephoto zoom- Minolta AF 100-300mm F4.5-5.6 D

An obvious retrofocus zoom (note two group structure) - Sony DT 18-55mm F3.5-5.6 SAM

Another retrofocus zoom- Canon EF 28-80mm f/3.5-5.6 II USM

Basically, if it has to go over 105mm at the long end it'll be a telephoto zoom, I've found from looking at lens diagrams. Hence the safe suggestions in the first post.

Whether a zoom is mechanically / optical compensated and how many groups its designed with won't change what you want to remove and what you need to avoid. Fundamentally afocal zooms have three key parts, even if the lens uses more than one group to do it's job.

The only one which throws me off is the existence of some two group zooms, like the Sony above, where the entire lens is those two groups- negative and positive against each other- and not four like above. But for adapting purposes, it would be the same (front does the focusing) if not simpler. I have never seen a two group telephoto zoom, they seem only for wides.

perhaps the Tamron's front should have been kept more intact (as 3 elements in 2 groups)?

I was pretty happy with the level of correction so didn't see the need to bother.

CORRECTION: Dpreview doesn't let you edit posts after people reply, which is annoying because- the Tamron's front group IS one housing.

The outer retaining ring pulls it all out, the inner retaining ring is for the front element. Guess which one I started with?

Why this error? Well, I lost the front element retaining ring ages ago when this lens was disassembled :-D I still have the front element, so when I put it back in it all clicked.

It's a strong positive power element that adds some pincushion distortion to the eye- I much prefer it just as a doublet.

 

[Eggplantt]

You may appreciate Art Vaughan's Flickr photostream for similar applications.

Some really thoughtful and creative work going on there, thank you for letting me know!