Bushnell 21mm vs Nikkor 18mm UV Transmission Test Comparison

[Cadmium]

UV Sparticle transmission test comparison.

Bushnell Automatic 21mm f/4.5.

Nikkor 18mm f/4.

 

Alex posted some lens comparisons here, including his test of the Bushnell 21mm, which was my favorite of those he tested:

http://www.ultraviol...ns/page__st__20

 

 

 

 

Added:

I forgot to mention that the Bushnell 21mm lens has a rear filter glass that attenuates UV and needs to be removed for UV photography:

 

[igoriginal]

Fascinating, Steve! Looks like you're on a roll.

 

There's also another variant on the Bushnell 21mm full-frame prime lens. This one, of aperture f/3.8 (instead of the f/4.5 variant which you've tested), and chances are that it might perform similarly (more or less), although no guarantees, of course.

 

Having a more compatible mount (M42) also helps its case.

 

See this: Bushnell Automatic 21mm f/3.8-16

[igoriginal]

The Nikkor 18mm F/4 is interesting, too. However, average asking prices for that lens tend to run between $400 and $600 USD, so not very realistic of an investment for most individuals.

 

Still, quite compelling of a find. Nice!

[Cadmium]

You missed the point Igor.

[igoriginal]

There are multiple points that can be inferred from this post.

 

Such as ...

 

1. That wider-angle UV-capable lenses do exist.

2. That just because a lens doesn't transmit UV as deeply as another lens, doesn't mean it's completely UV-useless.

3. That there are clearly many more UV-capable lenses out there, waiting to be discovered, and finding them is not as rare as previously assumed.

4. That using an array of narrow-bandpass filters CAN be a viable (and more accessible) alternative method for reliably testing various lenses for UV capability, without necessarily having to put them through a spectrometer analysis. A "poor man's spectrometer" test, essentially.

 

How am I doing, so far? :-) (With my deriving of points from such a post, that is.)

[Cadmium]

Poorly.

[igoriginal]

Ok, one other point to add:

 

5. That a comparison test of two lenses of similar focal-length range, similar F-stop values, and similar UV-transmission depth ... and yet, one can be drastically more financially-feasible than another ... is a very revealing and valuable insight.

 

Am I getting warmer? Haha.

[Alex H]

Thanks, Steve!

 

 

There's also another variant on the Bushnell 21mm full-frame prime lens. This one, of aperture F/3.8 (instead of the F/4.5 variant which you've tested), and chances are that it might perform similarly (more or less), although no guarantees, of course.

 

Having a more compatible mount (M42) also helps its case.

 

See this: Bushnell Automatic 21mm f/3.8-16

 

Igor, the lens you linked in your post is made by Tokina (not Tamron), it was sold under variety of names, including Asunama and Super Lentar, and is one of the lenses included in my test that Steve linked to (middle one in the back row). It comes in a variety of mounts.

 

Adapt-a-matic lenses have interchangeable mount system, most important of which for UV-shooters are M42 and Nikon (pre-AI if I remember correctly).

[igoriginal]

Igor, the lens you linked in your post is made by Tokina (not Tamron), it was sold under variety of names, including Asunama and Super Lentar, and is one of the lenses included in my test that Steve linked to (middle one in the back row). It comes in a variety of mounts.

 

Adapt-a-matic lenses have interchangeable mount system, most important of which for UV-shooters are M42 and Nikon (pre-AI if I remember correctly).

 

Yes, I am aware that Bushnell is a reseller / re-brander. That various of their lenses were sourced from multiple manufacturers was never under contention. Note, therefore, why I use the word "variant" to refer to different models that are otherwise stamped with the same name.

 

However, I failed to notice the adapt-a-matic mounting design, above. Thanks for pointing that out, Alex, as this escaped my attention.

[OlDoinyo]

Is there a legal reason that serial numbers must be obscured in these photos? If so, I may have been an unwitting violator in the past..

[igoriginal]

Is there a legal reason that serial numbers must be obscured in these photos? If so, I may have been an unwitting violator in the past..

 

That's what I want to know. :)

 

Especially on the Hedomar lens (in a different post), since I happen to have a copy of the same lens, and thus would be curious as to the range of serial numbers of the entire series. It would also allow one to form a concrete baseline of comparison, because I have seen in some cases where even within the same series production, critical changes have been made (ex: changes in the coatings), hence altering the UV transmission performance in otherwise the same optical construction. Therefore, building a knowledge-base of serial number ranges can be used to delineate where such changes take place ... thereby guiding would-be purchasers towards the more preferable releases, where applicable.

[Cadmium]

I sometimes blur the serial numbers of my lenses I show in example shots. I am 99% sure there are no rules about this either way, just a personal choice.

These photos are intended to compare the lens coating color and other physical comparisons between the lenses.

[igoriginal]

Ok. I respect that, Steve. It's just that I was seeking an answer, one way or the other. An answer is better than no answer. Thanks!

[Cadmium]

I forgot to mention that the Bushnell 21mm lens has a rear filter glass that attenuates UV and needs to be removed for UV photography (see first post in this topic with added photos showing rear of lens).

[Andrea B.]

Well that is interesting! What is that filter for anyway?

Is there any possibility of replacing it with a UV-pass filter (assuming appropriately sizing)?

[nfoto]

The filter has a slightly yellowish cast (at least, for the Tamron equivalent I have) and most definitively blocks UV. I removed it. Also had the beneficial influence of making the lens focus correctly to infinity on my Nikon D3200 with internal Baader U.

[Andrea B.]

I ask again: what was that filter for anyway?

EDIT: ignore this corssed-out repeat question. I missed the answer !!! Tired eyes.

 

And can it be replaced with a UV-pass filter?

[nfoto]

A. Part of the optical pathway. Put there because having small filter(s) in the rear is cheaper than huge filters in the front.

B. The filter shouldn't be there any way as you might lose infinity focus for UV.

 

The rear filter threads are tiny, around 16 mm if I recall correct. However, with some extra modification you would be able to get approx 30mm+ filters fitted to the end of the lens as the rear lens part is quite flat and is recessed from the surrounding bayonet.

[Cadmium]

Yes, mine has a slight yellowish color to the filter glass, and may have some other coating on it, but it is hard to tell. It may be something simple like close to Schott GG400 to cut UV.

Mine measures 13.9mm diameter x 1.25mm thick (which fits inside inner diameter of the threaded outer holding ring, you could use a slightly larger diameter if mounting under the threaded ring).

It will hold a filter up to 4mm thick maximum (if the threaded ring is not screwed all the way in).

The read photo I show above has the filter glass removed, but the threaded ring is in place. The glass you see in that photo is the rear optical element of the lens.

[Andrea B.]

Thanks, Steve and Bjørn !!!

 

(I flew through the first remark about blocking UV and missed it. My apologies, Bjørn!!)

[Cadmium]

Just a preliminary test of rear mounted Hoya U-360 13.8mm diameter x 2mm thick filter with the Bushnell (Tamron) 21mm lens.

This seems to work quite well, so I will make some UV-only stacks to try also.

The screw in ring allows for different thicknesses of filters/stacks.

Cloudy and rainy here.

 

 

[nfoto]

Hm. That looks quite IR-ish to my eyes. Perhaps a rear-mounted Baader U 1.25" would be better?

 

Just been out shooting this morning the first Tussilago flowers of the spring with my Tamron 21 mm f/4.5 on the Nikon D3200 (with built-in Baader U) and the broadband Panasonmic GH-2 (using a Baader U inside the lens adapter).

 

While the Tamron is no wide version of the Noflexar and similar UV-capable lenses, it does a very fine job and thus is a most welcome addition to the Nikkor 18/4 for "wide" UV pictures.

 

 

21 mm f/4.5 Tamron on Panasonic GH-2. f/16, 8 sec, ISO 100. Rear-mounted Baader U 2"

 

[Cadmium]

Hm. That looks quite IR-ish to my eyes. Perhaps a rear-mounted Baader U 1.25" would be better?

 

Just been out shooting this morning the first Tussilago flowers of the spring with my Tamron 21 mm f/4.5 on the Nikon D3200 (with built-in Baader U) and the broadband Panasonmic GH-2 (using a Baader U inside the lens adapter).

 

While the Tamron is no wide version of the Noflexar and similar UV-capable lenses, it does a very fine job and thus is a most welcome addition to the Nikkor 18/4 for "wide" UV pictures.

 

21 mm f/4.5 Tamron on Panasonic GH-2. f/16, 8 sec, ISO 100. Rear-mounted Baader U 2"

 

 

My test above is not UV, it is dual band IR, U-360 alone.

I haven't made any other filters for it yet, but I will post some shots when I do.

Thanks to Alex for the Bushnell/Tamron 21mm. Nice alternative to the 18/4.

[Cadmium]

ERROR update:

I had posted previously, "It will hold a filter up to 4mm thick maximum (if the threaded ring is not screwed all the way in)."

I have just now discovered that is wrong. I had failed to notice and include the slight 'domed/raised' surface of the rear element, which protrudes slightly above the surface of the back element holding ring.

This creates two problems, first that there is not as much room for filter thickness, and that there needs to be some separation between the element holding ring and the front of a filter, to separate the protruding element dome from the filter surface. So this will loose at least 1mm, or more. I will try with 1mm UG11 + 1.75mm S8612, but I am not sure yet if even that will fit now.

Sorry for my error in measuring this previously.

[OlDoinyo]

I am very interested in the final outcome of this endeavor, as I have one of these lenses as well and would like to know if a rear-mounted non-dichroic UV filter is possible without excessive IR leakage or losing infinity focus. Otherwise, we are back to an 82mm front-mounted filter as the only choice. Do keep us posted.

 

For those of you who use rear-mounted filters on cameras without live-view, do you compose the picture with an auxiliary sight? I have such a device, but it goes no wider than 35mm equivalent, and the aim is not always true. With front-mounted filters, I often compose without the filter and then screw it on to take the exposure; but this is no possible with rear mounting.