An odd lens

Started 7 months ago | Discussions
Bosun Higgs Regular Member • Posts: 103
An odd lens
7

When I bought the Taylor Hobson Type 250 100mm f2.8 lens there was nothing in the vendor's photos to give a sense of scale and the dimensions were not mentioned in the details. Similarly, the few images of this lens online had no size referents. In appearence, it looked very much like many of the old 16mm cine projection lenses that are availble, so the first surprise I got when I unwrapped it was the size. The lens is bigger than some of my 35mm cinema projection lenses.

The Type 250 alongside a 2" Taylor Hobson lens for 16mm cine. Similar appearance, just on steroids.

The next surprise was the lens barrel diameter, it is 57mm, or more likely 2.25 inches. Projection lenses generally fit into a range of standard sizes, 25.4mm (1 inch), 42.5mm, 52.5mm, 62.5mm and 70.5mm, I've never seen one of this diameter before.

The chromed brass barrel turned out to be merely a sleeve into which the much smaller lens body fitted. When unscrewed, the lens body was very compact for 100mm focal length, so I imagined it to be a Double Gauss derivative.

When I stripped it, the lens had yet another surpise for me, it had four elements, so it was not a Double Gauss. I have many projection lenses in my collection, most are Petzvals, fewer are Double Gauss, and a handful are triplets, this lens was not any of these designs.

A sort of back-to-front Ernostar?

I am not sure what type of lens this is, but the layout resembles a kind of back-to-front Ernostar. Designed in 1925 by Ludwig Bertele, the Ernostar was a clever modification of the triplet design that inceased the speed of the triplet considerably. Bertele named the lens after the firm he worked for, Ernemann.

I have never seen another projection lens of any make with a layout like this. I have many Taylor Hobson projection lenses, but they are all Petzvals, why they departed from their tried and tested designs for this particular lens is a mystery. If anyone recognises this optical formula, I'd love to know what it is.

Fitted on my A7RII with added hood.

I removed the chrome sleeve and simply mounted the lens body itself in a helicoid. The lens is very light and compact and handles well on the A7rII. It seems to be uncoated, but gives good contrast. There seems to be virtually no field curvature, which is a real novelty in a projection lens!

It is fairly sharp centrally, but this falls off rapidly, which is disappointing given the possibilities of its flat field.

The lens covers 35mm full frame completely with almost no vignetting, the image circle appears to be about 100mm, so it would probably be useful for medium format cameras such as the Fujis. I believe the lens was made to be used in a 35mm slide projector rather than for cine, which would explain the extensive coverage.

Soft bokeh bubbles.

Although the bokeh bubbles have soft edges, they still layer well.

The last of the Cherry Blossom here.

Not too shabby at close distances either.

I love what the lens does to OOF backgrounds.

Bokeh is surprisingly good given its pedestrian f2.8 aperture. Bokeh bubbles are soft with little outlining, but their size is obviously limited by the small aperture. Although soft, the bubbles do "layer" well and there is hardly any "catseyeing" even in the extreme corners. Non-specular distant background elements are blurred very smoothly, giving a pleasing "watercolour" effect.

I usually prefer lenses with exagerated bokeh effects or texturing, but I found that I really liked what this lens did to distant backgound features. Although there is no overt texturing, there is a "character" in the blur that is missing in the bland smoothness of modern lenses like my Sigma 135mm f1.8 ART.

I really was not expecting much from this lens given its modest aperture (and price!), so its bokeh rendering came as a very pleasant surprise.

Gesture Veteran Member • Posts: 9,027
Re: An odd lens

I may have missed it, but what do you think the original use was?

Thanks.

OP Bosun Higgs Regular Member • Posts: 103
Re: An odd lens

Gesture wrote:

I may have missed it, but what do you think the original use was?

Thanks.

I think it was used in a 35mm slide projector, also manufactured by Taylor Hobson. I dimly recall seeing a picture of this online, but I can't seem to find the site again. As the lens is uncoated, it must be fairly old.

OP Bosun Higgs Regular Member • Posts: 103
Re: An odd lens
1

Well, no wonder I couldn't find the lens online. It's actually a Kershaw, not a Taylor Hobson, duh!

The original comments in my post apply equally to Kershaw, they mainly produced Petzval projection lenses, with Double Gauss usually only used for the shorter focal lengths. I have many Kershaws and none them have an optical formula similar to this.

I would have sworn that the lens was a T&H, that'll teach me to wear my reading glasses more often!

OP Bosun Higgs Regular Member • Posts: 103
Re: An odd lens
2

Found it! Here's a pic of the Type 250 projector complete with lens.

Obviously a slide projector.

1950's vintage, I think.

Gesture Veteran Member • Posts: 9,027
Re: An odd lens

Do you have any Magic Lanterns?  What type of lens was used on those?

Thanks.

OP Bosun Higgs Regular Member • Posts: 103
Re: An odd lens

Gesture wrote:

Do you have any Magic Lanterns? What type of lens was used on those?

Thanks.

I have not tried any Magic Lantern lenses. These devices were produced for over two centuries, begining in the 1600's, so the term "Magic Lantern lens" covers a huge gamut of optics.

Prior to 1840 all types of lenses were manufactured on an ad hoc basis, produced by "eye" and experience, so variation in the layout and quality of these optics will be considerable. After 1840 Petzvals began to be used for Magic Lanterns, Petzvals were the first lenses produced following computation of optical laws and were extremely fast for the time.

So Magic Lantern lenses from the late 19th/early 20th century would probably be the sweet spot, unfortunately these lenses are very sought after by large format photographers and sell for a lot more than I am willing to pay.

fferreres Veteran Member • Posts: 6,987
Re: An odd lens

This is a nice looking lens, I usually like or adore simpler constructions that are in unique ways. How many different ways can focus light on a plane reasonably well? Apparently, infinite, and they don't do the same to the background.

I wonder where the aperture would go, and if maybe, the design itself lens more to projector lenses because of the lack of iris. I note that the Iris may not be easy to place given the tight spaces. It also seems this is a compact 100mm with regards to the aperture.

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