Greetings from Germany

[Tsubo]

Hey Andrea,

 

I'm not sure whether I have misunderstood your explinations. But as far as I can tell my Kecay adapter follow the same design as the Fotodiox only with an additional extendable barrel for increasing the FFD. At its minimum it extends the distance by approximately 25mm. Judging from the pictures of the Fotodiox adapter linked above, the base construction appears to be quite thick, as well...

 

You wrote that the standard mFT distance of 38.67mm should be increased by 6.79mm to fit (most of) the M42 lenses listed before.

Therefore, wouldn't I need an adapter that adds only ~7mm to the system?

 

 

In terms of modding the camera I think I will indeed perform the conversion myself. I feel like investing 300 euros on a mod for a camera with a present value of maybe 200 euros or even less (demand is low atm) doesn't quite keep the balance.

For now I will just try to remove the dust protection and filter. Being able to focus to infinity would be nice to have. But using only older non-native lenses it will persist to be a trial and error anyway I guess

 

By the way: thanks once more for your patience! :)

[Andrea B.]

The Wikipedia list of flange focal distances is as good as any. Here's the link: https://en.wikipedia..._focal_distance

And I think I see the source of confusion.

 

Micro Four Thirds System: 19.25 mm

Olympus PEN F (film): 28.95 mm

Olympus Four Thirds System: 38.67 mm

Olympus OM-mount: 46.00 mm

M42x1: 45.46mm

 

I saw "Olympus Four Thirds" in the chart and concluded you needed 45.46 - 38.67 = 6.79 mm of extension.

However, it seems "Olympus Four Thirds" is not the same as an Olympus digital camera having a Micro Four Thirds FFD which apparently is the FFD for a digital Olympus PEN camera.

 

So using the Micro Four Thirds FFD, the correct calculation is 45.46 - 19.25 = 26.51 mm of extension.

 

It would appear that Olympus makes two types of "Four Thirds" cameras ?? ?? ??

That could be somewhat confusing when trying to buy the correctly sized accessories!! So I hope you will excuse me for falling into that bit of confusion. I'll correct the original post to explain what happened.

 

---

 

I found my old D300 conversion -- which I did myself so it has no internal filter. Using the UV-Nikkor 105/4.5, I could focus to infinity by going past the infinity mark on the lens. Using the Coastal Optics 60/4.0 I could focus to infinity by staying short of the infinity mark on the lens.

 

What to make of those results? I'm not sure.

 

The lesson might be that if you have a lens which requires moving past the infinity mark to achieve infinity focus on a converted, filterless camera and that lens does not permit you to move past the infinity mark (as some lens do not permit this), then..... you won't get infinity focus without attempting some adjustment to the lens. And not all lenses can be ajusted to change the behaviour of their infinity mark.

 

Whew.......!!!!!!

[Tsubo]

Thank you for clearing that up!

Now the whole thing makes sense :)

 

The difference with recent Micro Four Thirds (mFT) mirrorless design is that they obviously moved the sensor closer to the front, reducing the flange focal distance. Those builds do also come with a smaller bayonet connector.

Hereinafter, the ~26mm should be a more realistic figure and easy to achieve with the helicoid adapter.

 

 

Also thanks for sharing your experience with the focus.

I think I can live with that and will try to find a combination that works for the occasional infinity focussing.

[nfoto]

A side note: Yes, Olympus did indeed make *two* 4/3 format systems. One is "Four-Thirds" (or "FT"), the other is "Micro Four-Thirds" or m43 (sometimes written mFT, m4/3, μ4/3, or variations thereof). The FT is the older system, with a reflex mirror, and in order to mount these lenses on an m43 system, one has to use an adapter which Olympus supplied (supplies still?). The "new" m43 is of course what we know today as a "mirrorless" system. It has the shorter register distance of the two systems.

[Tsubo]

Thanks for your addition :)

 

Besides, does anyone know a good alternative to the Baader U-Venus filter, being available in the EU? Maybe something a little bit cheaper but still with proper coatings?

Some IR pass wouldn't be an issue for me.

 

I measured the imaging circle at the front of the lens yesterday. The max. diameter without vignetting is about 22mm with my set of lenses on the mFT sensor (crop 2.0).

 

Do you have any tips for adapting the M28.5 threads to a 52mm (female) filter thread + a lens hood for the front?

 

I think about just tucking the filter into a Raynox snap-on shell and fix it with some "Sugru" modable glue. That would allow an easy way to mount and unmount the filter in the workflow. Furthermore, the Raynox DCRs come with a 49mm female thread on the lense part (whose glass I'd have to remove) which would allow me to add a standard lens hood.

Maybe a bit janky. But still better than adding many costy adapters to manage both the front and back.

[Andreas]

A cheaper alternative for expensive UV filters are stacks with for example UG11 and BG39 or S8612, there are some sellers from United States on Ebay.

Just a week ago I have ordered a set of two filters UG11 and BG40 (both with 37mm filter thread) for about 40€ + ~25€ (shipping and customs charges). They are still on the way, so I don't know how good these filters are. Usually the disadvantage of filter stacks with UG11 and one IR suppressing filter is that you lose some intensity and that you usually still have a larger infrared leak compared to the Baader U filter. I think the Baader U filter is worth the money.

Depending on your illumination condition even a small IR leakage of less than one percent can disturb your UV image.

 

A good overview with transmission charts of many UV transmitting or IR blocking filters are here:

http://www.ultravioletphotography.com/content/index.php/topic/1313-filter-transmission-charts/

[Andy Perrin]

Tsubo, I think you may be underestimating the extent of the IR problem. If there is too much IR, you literally cannot see any UV features at all. It’s not just slight contamination, it overwhelms the whole image. And my experience is that it’s actually pretty hard to get “slight” IR contamination. Generally it is an all or nothing thing. You either get a UV image or an IR image.

[Tsubo]

Thanks for your replies!

 

I thought that as long the IR transmittion does not exceed maybe 40% compared to 80% of UV in specs it would be fine. But if you recommend choosing UV only, then I will probably decide for the Baader Venus.

 

The stacked glass doesn't look very promising, yet. It may be a bit cheaper but also worsen the contrast, reflections and be more vulnerable to oxidation etc.

[Andy Perrin]

The stacked glass works very well! It is actually dichroic filters that tend to have reflection issues.

[ulf]

Due to the difference in normally available UV-light compared to the IR-light and combined with a much lower sensor sensitivity for UV than IR, a high IR attenuation is needed.

Was that long blurb possible to understand?

 

Even a leakage of 1‰ IR compared to the transmission of the UV can sometimes cause problems.

Baader U is, most times, good enough in attenuating IR and has one of the best UV transmissions.

 

Read this for a better understanding of IR-leakage:

http://www.ultraviol...__fromsearch__1

[Tsubo]

Thanks for the clarification! :)