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Metabones - Speed Booster
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PostPosted: Mon Jan 14, 2013 9:46 am    Post subject: Metabones - Speed Booster Reply with quote
Hi,
This hit the news last night: Metabones is proposing a new version of their Canon EF to Nex adapter with a focal reducer, allowing to compensate the crop factor, therefore increasing the aperture and improving the sharpness.
First tests here: http://philipbloom.net/2013/01/13/speedbooster/
Details here: http://www.metabones.com/images/metabones/Speed%20Booster%20White%20Paper.pdf

Any thoughts? Looking at mflenses that can be mounted on an EOS mount, this should apply to those ones too. And the optical principles could be re-used to build similar adapters to any mount


PostPosted: Mon Jan 14, 2013 11:04 am    Post subject: Reply with quote
Adding glass elements is a bad idea imho, usually sure to have a negative effect.

But this one might be okay, the high price suggests they have put some good class in there.

The concept is valid, but it doesn't really appeal to me, I prefer to use my lenses as the designer intended.


PostPosted: Mon Jan 14, 2013 11:41 am    Post subject: Reply with quote
iangreenhalgh1 wrote:
I prefer to use my lenses as the designer intended.

+1


PostPosted: Mon Jan 14, 2013 1:13 pm    Post subject: Reply with quote
iangreenhalgh1 wrote:

The concept is valid, but it doesn't really appeal to me, I prefer to use my lenses as the designer intended.

Once you use them on a crop camera, you could consider you're not in that case anymore and using this adapter gets you closer to it. Let's take their example, the 50/1.8 wide-open, on an APS-C sensor:
- without their adapter, you have the field of view of a 75mm lens, with the depth of field of a 75/2.8
- with their adapter, it behaves like a 35/1.2, so you have the field of view of a 50mm lens, with the dof of a 50/1.8 lens


PostPosted: Mon Jan 14, 2013 2:46 pm    Post subject: Reply with quote
ylyad wrote:
iangreenhalgh1 wrote:

The concept is valid, but it doesn't really appeal to me, I prefer to use my lenses as the designer intended.

Once you use them on a crop camera, you could consider you're not in that case anymore and using this adapter gets you closer to it.


Definitely not closer to the original, the extra glass will change the optic's "fingerprint".
Of course the adapter may be useful to people who don't want to spend more money for extra lenses
(although I suspect that the price of this adapter will be higher than the average used manual lens)
But "useful" is one thing, "truer" is another.


PostPosted: Mon Jan 14, 2013 2:49 pm    Post subject: Reply with quote
A quite old idea from astronomy adopted to modern lenses, a inverse teleconverter, i.e. a positive achromatic element.
We had discussion here about that already...

See also on my BLOG: http://photographyoftheinvisibleworld.blogspot.de/search?q=reducer

without reducer/telecompressor:


with reducer/telecompressor:


overall system changed from f4 to f1.6 and the focal length from 84mm to 34mm!

P.S.: there are three threads about that now here...


PostPosted: Mon Jan 14, 2013 2:56 pm    Post subject: Reply with quote
Very interesting Klaus! If you don't mind, I would like an explanation on how it's possible to increase the speed of a lens.

P.S. I have removed the thread in "official news" section. I can't find the third topic.


PostPosted: Mon Jan 14, 2013 2:59 pm    Post subject: Reply with quote
3rd thread is here : http://forum.mflenses.com/metabones-caldwell-photographics-speed-booster-t56010.html


PostPosted: Mon Jan 14, 2013 3:00 pm    Post subject: Reply with quote
Thanks John, removed.


PostPosted: Mon Jan 14, 2013 4:37 pm    Post subject: Reply with quote
Orio wrote:
If you don't mind, I would like an explanation on how it's possible to increase the speed of a lens.


I think the basic principle is that the light rays are converged by the telecompressor, reducing the image circle. So a crop camera receives more light hitting the sensor when using a telecompressor than without it. (Light falling in the image circle but not on the sensor is mostly absorbed by the black interior of a camera I believe.) Is that what you were asking?


PostPosted: Mon Jan 14, 2013 4:55 pm    Post subject: Reply with quote
Some early test shots are here:
http://philipbloom.net/2013/01/13/speedbooster/

To test the image quality / change in the lens' character, it would be interesting to see some comparisons of using full frame lenses on the following:
(i) full frame camera
(ii) full frame camera, cropped image
(iii) cropped camera
(iv) cropped camera + speedbooster
(v) cropped camera + speedbooster, cropped image

(i), (iv) have the same fov and dof.
(ii), (iii), (v) have the same fov and dof.


PostPosted: Mon Jan 14, 2013 5:34 pm    Post subject: Reply with quote
@Orio: I agree it changes the fingerprint. What I mean is that using a full-frame lens on a crop camera is already changing the intention of the designer, anyway.

Regarding the "acceleration": the glass actually shortens the focal length, optically. Aperture is the division of focal length by diameter of front glass, so reducing the focal length decreases the f-number, i.e. increases the aperture.


PostPosted: Mon Jan 14, 2013 7:04 pm    Post subject: Reply with quote
Just a general remark: Sometimes, I would really, really wish that people would read (and understand) a book about lenses and lens designs except just talk about them... Wink


PostPosted: Tue Jan 15, 2013 1:16 am    Post subject: Reply with quote
Super interesting.

I'll never get a chance to try it at those prices, hope they make a budget version with just the glass and no EF autofocus electronics.

While I'm dreaming, they can make me an Exakta - NEX version too Laughing


PostPosted: Tue Jan 15, 2013 9:44 am    Post subject: Reply with quote
Cheapest version is 400$ for Leica-R to Sony Nex. Maybe this one would be within your budget?

I'm wondering whether to go nex/metabones/fd lenses (which I collect) way. It opens fd "almost" full frame experience Wink. The only question that remains is what level of degradation this optical element introduces.


PostPosted: Tue Jan 15, 2013 1:20 pm    Post subject: Reply with quote
ylyad wrote:
Aperture is the division of focal length by diameter of front glass, so reducing the focal length decreases the f-number, i.e. increases the aperture.


Use of the diameter of front glass here can lead to errors. Wikipedia tells us that the f-number or relative aperture, N, is given by

N = f/D

where f the focal length of the lens and D is the diameter of the entrance pupil. Wikipedia also tells us that the entrance pupil is the optical image of the physical aperture stop as seen through the front of the lens.

Taking a Nikkor 50 mm f/1.8 Ai lens as an example (since I have one at hand) and measuring the Front Glass Diameter, FGD, and D with the lens aperture ring set to 1.8, I estimate ...

FGD = 32 mm, whence N = 50/32 = 1.56, and
D = 28 mm, whence N = 50/28 = 1.79.

Here the approximation, that FGD ~ D, is not too bad. However for the Nikkor 28 mm, f/2.8 Ais lens, and measuring D with the aperture ring set to 2.8 ...

FGD = 40 mm with N = 28/40 = 0.70, and
D = 10 mm with N = 28/10 = 2.80.


PostPosted: Tue Jan 15, 2013 2:17 pm    Post subject: Reply with quote
http://www.canonwatch.com/rumor-metabones-working-on-a-speed-booster-for-canon-fd-mount-lenses/

Prepare for another FD price increase soon... Wink


PostPosted: Tue Jan 15, 2013 2:27 pm    Post subject: Reply with quote
amazing!
thank you Klaus for your expertise on the subject and samples, makes it so much more plausible and credible.
more samples appearing on the net, e.g. using the same lenses on 5DIII and NEX7: http://www.eoshd.com/content/9474/prototype-metabones-speed-booster-equipped-nex-7-vs-full-frame-5d-mark-iii


PostPosted: Tue Jan 15, 2013 2:45 pm    Post subject: Reply with quote
sichko wrote:

Use of the diameter of front glass here can lead to errors. Wikipedia tells us that the f-number or relative aperture, N, is given by

N = f/D

where f the focal length of the lens and D is the diameter of the entrance pupil. Wikipedia also tells us that the entrance pupil is the optical image of the physical aperture stop as seen through the front of the lens.

Taking a Nikkor 50 mm f/1.8 Ai lens as an example (since I have one at hand) and measuring the Front Glass Diameter, FGD, and D with the lens aperture ring set to 1.8, I estimate ...

FGD = 32 mm, whence N = 50/32 = 1.56, and
D = 28 mm, whence N = 50/28 = 1.79.

Here the approximation, that FGD ~ D, is not too bad. However for the Nikkor 28 mm, f/2.8 Ais lens, and measuring D with the aperture ring set to 2.8 ...

FGD = 40 mm with N = 28/40 = 0.70, and
D = 10 mm with N = 28/10 = 2.80.

Sorry for the improper wording, many thanls for correcting Embarassed

But this not change the principle of the calculation: if you add glass to shorten the focal length without changing the entrance pupil, you'll reduce the f number i.e. "increase" the speed


PostPosted: Tue Jan 15, 2013 3:25 pm    Post subject: Reply with quote
Bille wrote:
Prepare for another FD price increase soon... Wink


Please, no... FD's is last affordable line of high quality lenses that yet not attracted people and made prices mad...


PostPosted: Tue Jan 15, 2013 3:39 pm    Post subject: Reply with quote
ylyad wrote:
But this not change the principle of the calculation: if you add glass to shorten the focal length without changing the entrance pupil, you'll reduce the f number i.e. "increase" the speed

Absolutely.


PostPosted: Tue Jan 15, 2013 4:02 pm    Post subject: Reply with quote
pavko wrote:
The only question that remains is what level of degradation this optical element introduces.


That's the problem. nearly 400 quid for something that may reduce the IQ of my lenses. I don't need the extra speed, I was out today shooting Tech Pan at 25 ISO in winter light in northern England and I never had to open my Hexanon 1.7/50 wider than 2.8.


PostPosted: Tue Jan 15, 2013 4:24 pm    Post subject: Reply with quote
The extra speed allows to reduce depth of field, but in that case, I'd assume that sharpness is not so much looked after Very Happy

The other useage is to increase the field of view, and that'd be different, especially on micro-4/3's


PostPosted: Tue Jan 15, 2013 4:37 pm    Post subject: Reply with quote
I don't like very shallow dof, sometimes it's okay but it's become hugely overused these days due to this bokeh fad.

I can sort of see the attraction of the wider field of view, but it's no replacement for a FF digicam imho.


PostPosted: Tue Jan 15, 2013 4:44 pm    Post subject: Reply with quote
ylyad wrote:
The other useage is to increase the field of view, and that'd be different, especially on micro-4/3's

I think that will be the most important factor for some people.
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