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Battle of the EF mount Speed boosters for m43rds

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#1 dabateman

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Posted 11 April 2021 - 07:15

I own two of the many 0.71x type speed boosters for micro four thirds camera systems

I have scanned these with my spectrometer. My light source is weak into the IR range and No integrated sphere was used. Read these plots at your own risk.

The Metabones Ultra 0.71x (Second version) with 5 elements in 4 groups.
Attached Image: Metabones EF_MFT_Speedbooster.jpg

UV cut off 352nm
50% transmission at 370nm

And the Viltrox 0.71x EF-m2 II speed booster with 5 elements in 4 groups
Attached Image: Viltrox_EF_mftM2II.jpg

UV cut off 356nm
50% transmission at 380nm

The Metabones has very fast Autofocus and will even work in focus stacking mode with a camera that has the hacked firmware. The Viltrox will not.

My light source is not strong in the IR range. So don't jump to conclusions in the IR range.

Edited by dabateman, 11 April 2021 - 12:47.


#2 Bernard Foot

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Posted 11 April 2021 - 08:12

Not brilliant for UV, then.

Is the sub-200 spike an aberration of testing set-up?
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#3 UlfW

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Posted 11 April 2021 - 10:52

View PostBernard Foot, on 11 April 2021 - 08:12, said:

Not brilliant for UV, then.

Is the sub-200 spike an aberration of testing set-up?
Yes it is.
The spike is due to that there is no or very little valid information out after the calculations based on reference measurements of the light source and of no light.
It is just noise.
When I prepare my spectrograms in the Lens Data section I truncate the data to the range with valid data, as the information is intended to be more formal.

David's diagrams above are OK the way they are, as we can ask questions and comment.

You can also see a tiny offset around 1-2% below 350nm. That likely is from internal crosstalk.

David, Is these measurements done correctly with a integrating sphere or are the absolute values not valid?

Edited by UlfW, 11 April 2021 - 10:55.

Ulf Wilhelmson
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#4 dabateman

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Posted 11 April 2021 - 11:38

I would say the absolute value isn't absolute. I don't have an integrating sphere and the light source is dipping down into IR range. These are easier to read then the raw data I like to post. But yes I now see it can be miss leading.


#5 UlfW

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Posted 11 April 2021 - 13:19

I think it is not too far off due to that levels you see in VIS, but not completely correct amplitude-wise.
The graph gives a good hint of the performance, if you know how to interpret it, but many people takes data output from instruments as absolutely true.

Measuring transmission correctly in optical components is tricky, even with correct equipment.
I guess that the long slope towards NIR is at least partly due to measurement errors for both graphs, but that the UV-cutoff and max amplitude in VIS are reasonable, but maybe not exactly correct.

I bet that with just some small shift of angle or position of the lens, the VIS-NIR part will change

Edited by UlfW, 11 April 2021 - 13:22.

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#6 dabateman

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Posted 11 April 2021 - 13:20

View PostBernard Foot, on 11 April 2021 - 08:12, said:

Not brilliant for UV, then.

Is the sub-200 spike an aberration of testing set-up?

Actually the Metabones adapter is great for UVA imaging. When I have used it with a quartz or fused silica lens, the grain in boosted light equals the loss of light due to absorption. But you gain a wider optically corrected field of view.
For the Canon 40mm STM you lose under a stop of light but grain wider field of view and thinner depth of field.
It pairs very well with a 365nm light source.

I was hoping the Viltrox would be better, but its actually worse in UV.
So if you can afford it the Metabones adapters are best all around for what they offer. Best correction, fastest autofocus, and more UV transmission.

The SvBony cut off is just below 300nm, but doesn't play well with all lenses as Bernard has shown. It can improve a bad soft lens though, like the Steinheil 50mm. Also will actually give you a faster shutter speed with more UV light in.