next dumb question: fractional dioptre add-on lenses?

[RioRico]

I'm a perv. I like front-mounted optical strap-ons, like filters, wide+tele adaptors, and +dioptre meniscus lenses, as well as Raynox adapters. A +1dpt lens changes the focal length of the combined optic slightly, but shifts the working distance down to 50-95cm, with reduced DOF. I estimate that a +0.5dpt lens would have a working distance somewhere around 90-160cm, far enough for headshot portraiture. Even a modestly slow lens should have rather thin DOF. But I can't find any. Does anyone here know of suppliers for +0.5dpt screw-ons?

[GrahamNR17]

I share your perversion

For wide or tele adaptors, take a look at the Olympus add-ons they made for the iS/L cameras - they're probably the best available, ditto the similar items from Kodak, Panasonic and Fuji. On my little digital, they're sharp to the edges Not so brilliant on full-frame 35mm, but more than acceptable. The Chinese stuff on ebay is universally crap

As for close-ups, I've never seen a +0.5. How about one of those really pervy "zoom" close-ups made by Hoya in the 70s and 80s? I have one, but never really put it through its paces.

[Minolfan]

I found a list: http://fuzzcraft.com/achromats.html
Only a Pentax 0.44 in your range. And I think it is not easy to find one in real life. Cannot you ask you optician to put a glass fot spectacles in an old filter frame? Should not be too expensive. No nice achromat to get so, ofcourse.
I use a Minolta achromat 1 (0.94) on 85 - 135mm lenses, works certainly pleasant. Got it (like) new in original packing for € 2.50 in a box for sale in a photoshop

[kds315*]

Yes, I have a 0.4 diopter in 72mm diameter if you need one.

[Sevo]

I have a 67mm 0.5dpt Heliopan Achromat. Sub 1dpt achromats in big diameters weren't altogether uncommon up to about 30 years ago, as conventionally designed long lenses (upward of 250mm) generally were limited in close focus to some 2-5m, due to the weight/stability trade-off of long-throw helicals. Zooms and internal focusing later moved the close range in and killed that niche.

But small diameter dioptres in values below 1dpt might be much rarer, if they exist at all - even close range challenged systems had their normal lens close limit at or below 1m, and the bulk of SLR lenses went down to 0.7-0.3m, so that the appropriate dioptre starting value would be 1dpt at the very least.

[kds315*]

Yes indeed, diopters < 1 dpt are pretty rare and hard to find esp. achromats. I have both types in 0.4 dpt. found after some long search.

[scsambrook]

Fractional diopter lenses in diameters 55mm or larger were supplied by some makers in the 1970s, usually for their zoom lenses which had closest focus distances that were anything but close. I have +0.5d made by Sun, which going by its thickness must be an achromat. It works okay. Kodak also made them for the 135 Retina Tele Xenar, designated NI and NII. They sometimes turn up on eBay, which is where I got my pair.

The optician is a good idea, but it might not be cheap. I recently checked this in connection with another hare-brained idea of mine. The man said £20+ VAT = £24 for a disk up to 60mm diameter and that was plastic not glass. Maybe not the way to get really high quality.

[RioRico]

Thanks for the responses! Part of my reason for inquiring is that I recommend odd stuff on various forums, and a source of inexpensive <+1dpt magnifiers would be handy. But if none such exists... well, that's life. The article I'm writing on STUFF TO PUT IN FRONT OF YOUR LENS will have a hole in it.

@Graham,
Thanks for the Olympus-Kodak-Panasonic-Fuji recommendations. Yes, I skip the cheap Chinese strap-ons. My best now are Sony and Kowa.

@Minolfan,
Thanks for the list of achormats. And I've been hunting for round spectacles but even odd-shaped ones might work (jammed into adapter rings and masked) if they're large enough. Maybe I'll sacrifice some of my old glasses.

@Klaus,
Thanks for the offer. What were you thinking as to price? Hmmm, but shipping from Germany to California might be costly...

@sevo,
Large ones existed more recently too. I had a Tamron AF AL 28-200, probably 15 years old. It included a 72mm close-up, I think just +1dpt, that I sold with the lens. Didn't think I'd need to keep it.

@Stephen,
You're right, an optician wouldn't be cheap. I thought to ask a glass shop if they could cut down welder's glass for a ND666 filter; maybe they'd do spectacles too?

[aoleg]

I have a Pentax T160 attachment in 52mm filter size. It's SMC coated, about 0.625 dioptres (ref. http://kmp.bdimitrov.de/misc/macro/index.html). Used with SMC Pentax 85/1.8, it allows focusing a little closer for those face-only portrait shots.

[RioRico]

At the other end of the dioptre range, I just won a +20dpt close-up strap-on. I'm not expecting much in the way of IQ from it, but it's cheap at US$9 shipped. Maybe it will arrive before I go traveling; maybe not, and I'll have to stack two +10dpt pieces.

You may wonder, why bother? Well, they're fun and cheap and small. And something funny happens when +20dpt is stacked onto a +8dpt Raynox DCR-250: it becomes a roughly 35mm f/0.95 frankenlens. Put a 42-41mm step-down ring on the Raynox, then an M42 adapter, then onto the camera -- nothing faster! Horrible aberrations, of course.

ObTopic: I'm ready to sacrifice old eyeglasses to make a fractional dioptre lens. But I guess I can't advise newbs to do so, to turn their kit lenses into portrait marvels. Ah well...

[Minolfan]

Doesn't come out something interesting glass when you dismantle a stuck zoomlens?
I have a AF Sigma 70-300mm that doesn't work anymore. No idea what is in it

[RioRico]

[Sevo]