Fujinon 300mm & 360mm W puzzle

[xkaes]

Here’s a question for anyone familiar with the Fujinon W and NW lenses – particularly the 300mm and 360mm lenses, which have an interesting difference from the others in the series. Complicating the matter is that not only did the Fujinon lenses actually change over time, the information in the Fuji literature changed – some correctly and some not, and it can be difficult to know what changes were correctly listed and which were not.

The original W series – single coated lenses with the inscription inside of the filter ring – all had a 6/4 lens design, and an angle of coverage of supposedly 80° (except for the 150mm f6.3). The “supposedly” will become apparent in a moment.

Around 1980, Fuji made some big changes to the W series by creating the NW series. All of the W series lenses (except for the 150mm f6.3) saw some changes – some minor, but most not. Interestingly, the 300mm and 360mm lenses (along with the 150mm f6.3) were not designated as NW lenses.

All of the new NW lenses, and the 300mm and 360mm W lenses (except for the 150mm f6.3) were now marked on the outside of the filter ring – on the barrel – with a W, not NW. And all of them (except for the 150mm f6.3) were now EBC multi-coated.

Another big change is in the lens designs. The NW lenses from 105mm to 180mm are now all 6/6 air-spaced lenses, while the 210mm is now 6/5. Interestingly, the 250mm, 300mm, and 360mm remained 6/4.

As one would expect, these changes resulted in different angles of coverage. The 6/6 lenses, are now all 76° lenses, while the 210mm is reduced to 71°, and the 250mm dropped to 64°. But unlike the 250mm – which retained the 6/4 W design -- the coverage for the 300mm and 360mm W lenses stayed at 80°, and their image circle did not change either.

However, two years later, in 1982, Fuji came out with a new sales brochure with some changes for the 300mm and 360mm W lenses. They are still listed as W lenses but the angle of coverage is reduced to 70° and 68°, respectively – but the image circles are reported as the same as in 1980. I assume this means that the 1980 brochure was incorrect, and that the 1982 brochure is inaccurate for the image circles of the 300mm and 360mm W lenses.

It's also possible that the original 300mm and 360mm W lenses did not have coverage of 80°.

So, I’d like to get a more accurate estimate for the image circles of the first and last 300mm and 360mm W lenses.

I'd also be interested in any speculation why these two lenses were never designated as NW lenses – because in every respect they seem almost identical to the 250mm NW lens. Could it be that their original coverage in the W series was lower?

[Maris Rusis]

I use a Fujinon-W 300mm f5.6 lens as standard on my Tachihara 8x10 camera. This lens appears to be multicoated and has the inside lettering. The serial number 450xxx puts it as late 1970s or early 1980s, I think.

Using maximum camera movements suggests to me that this lens has an image circle, or at least a circle of illumination, of nearly 500mm or by simple geometry nearly 80 degrees.

[xkaes]

Thanks for the response.
I've never seen a W lens with inside lettering that is multi-coated. Can you provide a picture?
The original 300mm is listed with an IC of 420mm (80°) at f22.

[rawitz]

The original 300mm is listed with an IC of 420mm (80°) at f22.

In the broschure we see an inconsistency in the datas of the 300 and 360 WS lenses. The given image circles of 420 and 485 mm do not match the stated image angle of 80°, compared to the 250WS with 80° and 398 mm IC.

It's also possible that the original 300mm and 360mm W lenses did not have coverage of 80°.
So, I’d like to get a more accurate estimate for the image circles of the first and last 300mm and 360mm W lenses.
I'd also be interested in any speculation why these two lenses were never designated as NW lenses – because in every respect they seem almost identical to the 250mm NW lens. Could it be that their original coverage in the W series was lower?

I think so. The 80° "coverage" of the WS series with an "older" lensdesign was very optimistic, and for the longer 300 and 360 lenses the spread between 80° illumination circle and image quality circle became so big, that the data specs "reduced" the image circle from ca. 500mm (300mm 80°) to 420mm 70°. The later CM/Wseries had a new lens design also for the 300 and 360 with IA of 69°/68° and IC 412/485mm.

[xkaes]

In the broschure we see an inconsistency in the datas of the 300 and 360 WS lenses. The given image circles of 420 and 485 mm do not match the stated image angle of 80°, compared to the 250WS with 80° and 398 mm IC.

The numbers in the EARLY W series literature might be wrong, but as Maris (above) points out, it seems the 300mm has a very large IC. The IC numbers -- if the coverage is really 80 degrees for all lenses seems accurate:

210mm -- 352
250mm -- 398
300mm -- 420
360mm -- 485

Nothing seems unusual there.

And in the 1980 literature, the exact figures appear for the NEW 300mm & 360mm W lenses -- although not marked NW lenses -- still 80 degrees of coverage with the same image circles.

The change occurs with the 1982 literature, when the angle of coverage of the 300mm & 360mm W lenses is listed as 70° and 68°, respectively, but the image circles don't change. Either the angle of coverage stayed the same, or the IC must be smaller -- or something else!

I just can't figure out where the screw-up(s) is -- and hope others find this interesting, or at least intriguing.

[rawitz]

210mm -- 352
250mm -- 398
300mm -- 420
360mm -- 485

Nothing seems unusual there.

It is - its mathematically inconsistent. The quotient between IA and IC has to be always constant. If for the 250WS with IA 80° we have an IC of 298 mm, the factor is 1,6x (IC to focal-no). For the 300WS (300x1,6) we should have an IC of 480mm, but the specs say 420mm, for the 360WS 576mm not 485mm. So IC and IA specs dont match, as I said above. There is only one modern lens 300mm with 80°, the Rodenstock Sironar WS 300, and the specs for this lens says 80° and 480mm IC which is consistent.
The "downgrading" of the spec-given ICs of the 300WS and 360WS from the theoretical IA value is I think resulting from the degrading image-qualitiy to the I-border. The inconsistency was later corrected in matching down the IA spec to 70° despite the lens being unchanged.

[xkaes]

I always thought that the coverage would decrease as the focal length increased -- as it does with the NW series -- but at the time of the early W series lenses with, supposedly 80° coverage, Fuji was making a 300mm SW lens with 100° coverage and an IC of 720mm. So I missed the "red flag".

Is there a way to compute the angle of coverage of the 300mm & 360mm W lenses from the listed IC -- that assumes the IC is correct, of course.

[xkaes]

There is only one modern lens 300mm with 80°, the Rodenstock Sironar WS 300, and the specs for this lens says 80° and 480mm IC which is consistent.
The "downgrading" of the spec-given ICs of the 300WS and 360WS from the theoretical IA value is I think resulting from the degrading image-qualitiy to the I-border.

That may well be, but Maris (above) says his 300mm W has an IC of "almost 500mm". Another fly in the ointment.

But perhaps that is why FUJI changed the angle of coverage in the 1982 literature. Originally, they listed a small IC, but not a decreased angle of coverage, due to the "usable" image. Later, they listed a decreased angle of coverage to match the usable IC.

That make sense to me!

Anyone have any other thoughts?

[rawitz]

I always thought that the coverage would decrease as the focal length increased -- as it does with the NW series -- but at the time of the early W series lenses with, supposedly 80° coverage, Fuji was making a 300mm SW lens with 100° coverage and an IC of 720mm. So I missed the "red flag".

Is there a way to compute the angle of coverage of the 300mm & 360mm W lenses from the listed IC -- that assumes the IC is correct, of course.

Given the identical lens construction (!) as the Fujinon WS series is, the IA has to be always the same -here 80°- and so mathematecally if you double the focal length you double the IC. The SW series is a fully different lens construction.

[rawitz]

That may well be, but Maris (above) says his 300mm W has an IC of "almost 500mm". Another fly in the ointment.

But perhaps that is why FUJI changed the angle of coverage in the 1982 literature. Originally, they listed a small IC, but not a decreased angle of coverage, due to the "usable" image. Later, they listed a decreased angle of coverage to match the usable IC.

That make sense to me!

Thats it!