Yongnuo 50mm f/1.8 – Initial tests

[bvf]

The post at https://www.ultravio...__fromsearch__1 raised the question of whether the Yongnuo 50mm f/1.8 and the Mk. II were indeed good for UV, as indicated on the Kolarivision site.

 

I have bought a second-hand copy of the original (i.e. not Mk. II) version and done what testing I can with the limited tools at my disposal. Below is a comparison with the UV-friendly Focotar-2 50mm f/4.5 and the not-very-UV-friendly Canon EF 50mm f/1.8 STM.

 

Summary (Spoiler!)

 

For me this is an unattractive lens. Low-quality build, and mediocre performance in the visible. For UV it is marginally better than the Canon 50mm, but way behind the known UV-friendly lenses.

 

First impression of the lens.

 

Yuk! I can only describe it as being of Fisher-Price construction. All plastic (although presumably the optics are glass!), with wobbling components. If you put it on the ground on a windy day it would blow away.

 

(The Mk. II sounds better in terms of construction, although I haven’t seen one. And I don’t know if that has different optics. But it costs about the same as the Canon lens so I can’t see who would buy it – unless it is significantly better for UV than its predecessor being tested here.)

 

UV Reach

 

All I can do to assess this is to compare exposures through the three UV bandpass filters I have – 380BP20, 345BP25, 315BP20. The following table gives the relative exposure factors (for flash) for the 345BP25 and 315BP20 compared to the 380BP20 – i.e. exposures normalised to 1 for the 380BP20 for each lens:

 

 

This shows that the Yongnuo and Canon transmission at 345nm is very low compared to the Focotar-2, although you could still form an image with the Yongnuo and possibly with the Canon. Neither the Yongnuo nor the Canon could form an image at 315nm.

 

Performance with a Baader U.

 

So the UV reach is poor. But if you’re not interested in reach and want to make images through a filter like the Baader U, how does the Yongnuo perform? Like the Canon, the Yongnuo can create images through a Baader U – examples below.

 

I had problems doing the WB (against PTFE) for the Yongnuo and Canon – using RawTherapee, the sliders came up against the stops and I was not able to get a completely neutral grey. But you can see more colour in the Focotar-2 image.

 

Exposures were longer for the Yongnuo and Canon than for the Focotar-2. For the outdoor (cloudy, dim, wet day) shots at indicated apertures of f/8, the Yongnuo was about 1.9 x Focotar-2, and the Canon was about 2.5 x Focotar-2.

 

In the images below, the top image is the Focotar-2, the middle image is the Yongnuo, and the bottom image is the Canon.

 

 

 

 

 

 

 

 

 

 

NOTE: these flowers are artificial!

 

 

 

 

 

 

Image Quality

 

Hopefully the following images are self-explanatory.

 

 

 

 

[dabateman]

Canon STM looks better than Yongnuo in all tests. If your white balance is trust worthy, the STM looks to be less purplish /blue, which would actually indicate that the STM goes deeper into UV than the Yongnuo. It likely that the peak maximum are just different, as in the STM has a gentle slop ftom 370 up to 400, but maybe the Yongnuo is steeper at 380nm plus. Thus more signal but less UV reach.

 

That's what it looks like to me. Or your colors are off and its all a wash. Can you return the Yongnuo? Sounds like a bad door stop, as it blows away in the wind.

 

[Andy Perrin]

Well, that's one lens I won't be buying anytime soon. All in all, this test was a great ad for the Focotar-2.

 

Yuk! I can only describe it as being of Fisher-Price construction.

Hee!

[bvf]

Canon STM looks better than Yongnuo in all tests. If your white balance is trust worthy, the STM looks to be less purplish /blue, which would actually indicate that the STM goes deeper into UV than the Yongnuo. It likely that the peak maximum are just different, as in the STM has a gentle slop ftom 370 up to 400, but maybe the Yongnuo is steeper at 380nm plus. Thus more signal but less UV reach.

 

That's what it looks like to me. Or your colors are off and its all a wash. Can you return the Yongnuo? Sounds like a bad door stop, as it blows away in the wind.

 

 

I'm not sure that the WB is trustworthy - as I mentioned, I had difficulty getting the WB for the Yongnuo and the Canon using RawTherapee. If someone else wants to have a go with other software I'm happy to let them have the files.

 

The reason I thought the Yongnuo was slightly better was because of the exposure factors for 345nm and because the Yongnuo exposure was slightly less at 380nm (assimung the indicated apertures are accurate).

 

It's not worth trying to return the lens - it only cost £40. If I really never use it again, it might find its way to ebay.

[bvf]

 

All in all, this test was a great ad for the Focotar-2.

 

 

 

Yes, you're right. Although the max-aperture tests are biased towards it because it's only f/4.5. Pity they're somewhat scarce and pricey (but still less so than the elusive Kuri).

[dabateman]

I have wondered how the Techart LM-EA7 would perform on your A6000. I know that comes out of left field, but I have autofocus adapters on the brain. A crazy idea to autofocus any UV lens in UV.

Fro what I have read its optimized for the A7R2, but will work on the A6000, just not reliably.

If you ever see one cheap and want AF for your manual lenses, let us know how it works out.

[ulf]

I have wondered how the Techart LM-EA7 would perform on your A6000. I know that comes out of left field, but I have autofocus adapters on the brain. A crazy idea to autofocus any UV lens in UV.

Fro what I have read its optimized for the A7R2, but will work on the A6000, just not reliably.

If you ever see one cheap and want AF for your manual lenses, let us know how it works out.

 

There seam to be some reliability issues with that adapter:

https://phillipreeve.net/blog/review-techart-pro-leica-m-sony-e-autofocus-adapter/ :

*update*

Please read this thread over at FM carefully. It seems that there is a design fault which will eventually lead some wobble of the adapted lens. Until this issue is fixed by Techart I would advise against buying the LM-EA7.

[dabateman]

Seems like a mixed bag. There are 48 pages to that thread. Fred comes back to buying another TAP adapter on page 46 and loves it again.

But you may win and not get the wobble or loose and get the wobble.

Fred also said that the AF on Z camera isn't as good with Megadap as Sony with the Techart.

[bvf]

I'd never heard of the Techart LM-EA7 before. There is one for auction on ebay right now, with a single bid at £26 - but there are 5 days to go.

 

This device sems to be specifically for Leica M lenses on Sony E. But there are cheap Chinese devices with descriptions like "Techart LM-EA7 AF Lens Adapter for Canon FD Lens to Leica M L/M Mount Camera" which I assume are used in combination with the Techart device.

 

Actually, for static subjects (and all my UV subjects are static) I prefer to focus manually using LiveView & magnifier - even for visible light images. Similarly when using my DSLR on a tripod. And when using the 315BP20 filter, the image is too poor (or even non-existent) for AF to work - I use tables & graphs I've made to re-focus after having focused using 345BP25 or 380BP20.