APS-C format UV capable fast lens?

[Avalon]

Could normal photography fast prime lenses be use for UV photography? I want to buy very fast APS-C format lens. Unfortunately fused silica or UV lens are rare and cost too much and finding cheap fast normal lens is a challenge. Best speed and price ratio I could find was Kamlan 50mm F/1.1 lens. It is great price for such high aperture lens and from reviews I can see that image quality is good enough, there is some softness on edges but it's totally acceptable. What is not clear to me is how lens will perform in ultraviolet spectrum. I will mainly focus 365-370nm range to do UV reflectography.

 

[eye4invisible]

Lens speed does not necessarily translate to UV performance. For example, my EL-Nikkor 80mm f/5.6 is a slightly better performer (shutter speed wise) compared to my Rodenstock 50mm f/0.75, and the EL-Nikkor is a lot easier to focus (and handle!)

 

A wider aperture obviously helps, but the coatings (or lack thereof) also make a big difference. There's even difference in performance between the different generations of the same lens make/model.

 

That being said, once I get my Sony A7 converted to full spectrum, there are a number of APS-C and C mount lenses I'm interested in testing (recently bought a Fujian 28mm f/1.4 in C mount, for example).

[Andy Perrin]

To make a visual analogy, it’s as if we are taking photos through sunglasses. It doesn’t matter how wide your aperture is if the lens is opaque!

 

The best UV performing ordinary lenses (known to us) are listed in the lens sticky. There may be others not yet known, but they are unlikely to be modern lenses because of the coatings and cement.

[WiSi-Testpilot]

I am using the Sony SEL 16mm 2.8, SEL16F28. It contains only 5 elements.

The photo was taken with a Baader U-Filter (ZWL 350 nm, Bandwidth 60 nm). It shows two charges of our PMMA-glass, which are not visible in the visible region. For your 365-370nm range the lens may be ok.

Best regards,

Wilhelm

[Avalon]

What lens were tested to be good for UV photography? I expect cheap lens should contain minimum amount of optical elements. Most lens have at least single layer AR coating. Is optical cement really opaque to UV in 365nm range?

[Andy Perrin]

Most cements are opaque. Here are the list of tested lenses:

 

http://www.ultravioletphotography.com/content/index.php/topic/1654-sticky-uv-capable-lenses/

[Avalon]

How about building own UV fused silica lens? Just single 25,4mm convex lens should do the job. Only problem is that this way there is going to be problem of corner blur or barrel distortion so for good image quality more complex optical system might be required.

[Andy Perrin]

You can mount a quartz singlet easily but it will be a poor quality lens I’m told. Why not just do what everyone else does and buy from the above list?

[ulf]

You can mount a quartz singlet easily but it will be a poor quality lens I’m told. Why not just do what everyone else does and buy from the above list?

An example of the poor imaging quality:

http://www.ultravioletphotography.com/content/index.php/topic/2992-infrared-block-broad-uv-and-visible-pass-filter/page__view__findpost__p__24022

[dabateman]

The only fast lens that might work that I know of that I don't think people here have tested is the Yongnuo 50mm f1.8 in Canon EF mount.

Lenstips transmission curve looks promising:

 

https://www.lenstip.com/425.9-Lens_review-Yongnuo_YN_50_mm_f_1.8_Ghosting__flares_and_transmission.html

 

However, you would have to get the Ef version as I read the optics for others were different. At least it is a very cheap lens.

[Dmitry]

Today I received the first version of the Kamlan 50mm F/1.1 lens (design 5/5). There is also a mk-II lens in 6/8 design, bigger and heavier - don't be confused!

 

A quick test using a 365nm LED showed excellent light transmission. More tests later in new topic

[OlDoinyo]

Because of their larger diameter, fast lenses tend to have greater center glass thickness. This makes them tend to have poorer bandpass. They also may be more prone to chromatic aberration wide open. 

[ulf]

A fast lens might appear to have a good UV transmission due to the wide aperture and in that sense it can be fast wide open.

Almost all lenses has worse performance when used wide open regarding all kinds of distortion and aberrations.

Lenses designed for the visual range are corrected for that.

The effect of the correction might make the performance worse outside the corrected range, like in UV

 

For a rather monochrome light source like an UV LED some of those aberrations are not visible.

[SteveE]

I too have noticed my M43 Kamlan 50mm f1.1 lens (original version) appears at first blush to have useful transmission. I was going to try to do some quantitative tests but lost access to the projection screen painted wall I was planning on using as a target to reflect my torch in a reproducible manner. Perhaps this suggests that the inexpensive 3rd party M43/APS-C lenses might be a good ground for investigation.

 

Steve