brian

brian

Lives in United States Petersburg, VA, United States
Works as a lens designer, photographer, entrepreneur
Joined on Oct 2, 2000

Comments

Total: 21, showing: 1 – 20
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In reply to:

orchidofiets: I miss the compatability of the Canon EF 100-400 and 400 mm lenses. These are to be found in mint condition for under €1000 and would make a great 600mm tele. Most probably sharper then Pana's 100-300 and cheaper then the still-to-come Oly 300 f4.

I think the EF 100-400 and 400 simply haven't been tested.

Direct link | Posted on Jul 30, 2015 at 05:32 UTC
In reply to:

Francis Carver: Let me see now if I get the lowdown here.

First, I buy a M4/3rd camera. But no lenses for it.

Next I buy a pricey Metabones lens adapter.

Them, I buy some Canon lenses.

Shake or stir and pour over ice, maybe?

"I also have not heard that wide converter inherently improve IQ but if you indications otherwise, I'd be happy to be corrected on that."

Actually, front-mounted wide converters suffer from three serious drawbacks:

1) They always add lots of bulk. (focal reducers *reduce* bulk)
2) They cannot increase the lens speed
3) They always increase aberrations,

See my new article "The Perfect Focal Reducer": http://www.metabones.com/assets/a/stories/The%20Perfect%20Focal%20Reducer%20(Metabones%20Speed%20Booster%20ULTRA%20for%20M43)%20-%20Whitepaper.pdf

Direct link | Posted on Jul 27, 2015 at 22:51 UTC
In reply to:

Francis Carver: Let me see now if I get the lowdown here.

First, I buy a M4/3rd camera. But no lenses for it.

Next I buy a pricey Metabones lens adapter.

Them, I buy some Canon lenses.

Shake or stir and pour over ice, maybe?

"Okay, Okay -- so only Metabones adapters improve IQ, and nothing else improves IQ -- okay, okay I get it now."

I'm really glad that you are the person to articulate this simple truth!

Direct link | Posted on Jul 27, 2015 at 22:45 UTC
In reply to:

RichRMA: Apart from a select few, who would want to use Canon lenses on a m4/3rd? Long lenses, maybe because there are no Olympus or Panasonic long lenses available aside from old 4/3rds lenses. Meanwhile, the Metabones thing might be less expensive if it were made to work WITH m4/3rds lenses.

junk1:
The reason that EF-S lenses aren't officially supported is that they all have a plastic shrould in the rear that interferes with the Speed Booster. However, most, if not all, EF-S lenses can be made to work by simply removing the plastic shroud. In most cases this can be done using fingers only - no tools.

Direct link | Posted on Jul 25, 2015 at 19:25 UTC
In reply to:

Mssimo: Found some great pictures of the sensor and lens design. Should be added to the article if possible. http://www.boulder.swri.edu/pkb/ssr/ssr-ralph.pdf

Here's another article that details the optics a bit more: http://www.corning.com/media/worldwide/csm/documents/Diamond_turned__Hegge.pdf

Direct link | Posted on Jul 22, 2015 at 11:38 UTC
In reply to:

ProfHankD: Very impressive bit of optics in a very cramped space.... Does this mean that it is now feasible to do an APS-C version with no crop relative to FF, i.e., 0.67x instead of 0.71x (or 0.726x for some competing focal reducers)?

Hank:
I forgot about the possibility of Sony-E to m4/3 adapters.

The image circle - or perhaps I should call it the illumination circle - of a lens+Speed Booster depends on the native coverage of the lens and its exit pupil location. The Speed Booster itself has greater coverage for lenses with a short exit pupil distance. So its difficult to come up with a single number here.

Direct link | Posted on Jun 10, 2015 at 13:20 UTC
In reply to:

spatz: Brian: with the speedbooster for the BMCC and BMPCC, some people showed it could in fact be used on other M43 cameras with electronic shutter. Do you envision that future M43 cameras able to use a fully electronic shutter will also be usable with this speed booster, so we no longer need device-specific models, or is the difference in filters / microlenses etc really a limiting factor? It would be great if you could make a comparison in image quality with the same lens, and different speedbooster / camera combinations.

Unfortunately, I can only react to changing conditions imposed by camera makers. I wish that m43 cameras were more uniform in their mechanical and filter design, and that that design were more Speed Booster "friendly". But given the nature of companies I doubt that will ever be the case.

So, given this reality, my goal is to provide the most useful specifications and best image quality possible for the major types of m43 cameras.

Regarding the Blackmagic Speed Boosters, its true that Andrew Reid and others were able to use them on other cameras like the GH4, but there was mechanical interference with the shutter and the image quality suffered since these Speed Boosters were optimized for the thinner Blackmagic filter stack.

Direct link | Posted on Jun 10, 2015 at 13:07 UTC
In reply to:

RichRMA: The telescope world has had this kind of device (almost the same reduction/speed increase) for 25 years and it supports FF. They were designed to shorten f/10 telescope focal ratios to f/6.3.
http://www.celestron.com/browse-shop/astronomy/astroimaging-accessories/reducers/reducer-corrector

Rich:
That's true. However, designing a focal reducer for a telescope with an incredibly long working distance and a slow f/6.3 throughput is far easier than designing one for short working distance SLR lenses and an f/0.80 throughput.

Direct link | Posted on Jun 9, 2015 at 17:43 UTC
In reply to:

ProfHankD: Very impressive bit of optics in a very cramped space.... Does this mean that it is now feasible to do an APS-C version with no crop relative to FF, i.e., 0.67x instead of 0.71x (or 0.726x for some competing focal reducers)?

Hank:
I recall seeing some beautiful circular images many years ago taken with 4x5 view camera lenses on 8x10 film. A focal reducer would allow you to do the same sort of thing. However, attaching an m43 reducer to Sony-E mount would be a very non-trivial modification task.

Direct link | Posted on Jun 9, 2015 at 17:35 UTC
In reply to:

Dr_Jon: It's a bit of a shame that Kipon have an m43 adapter that seems to give really good AF with Canon lenses and MetaBones have one that does nice focal reduction but no-one has combined the two. It would be okay but they are expensive products and it is a tough choice on whether to wait for someone to sort this out or not. (I suspect for video use, where MF is more the way to go, it matters less.)

http://www.eoshd.com/2015/05/autofocus-is-mega-fast-on-new-kipon-canon-ef-lens-adapter-for-micro-four-thirds/
(BTW I'm impressed they didn't edit out the times it had to hunt for focus.)

Dr_Jon: Extenders can be attached to Speed Boosters, although it might make more sense to just use a plain glassless adapter instead. For example, a 1.4x extender combined with a 0.7x reducer gives a net 1.0x - e.g., you've gone through a lot of glass to accomplish essentially nothing!

Direct link | Posted on Jun 9, 2015 at 17:27 UTC
In reply to:

ProfHankD: Very impressive bit of optics in a very cramped space.... Does this mean that it is now feasible to do an APS-C version with no crop relative to FF, i.e., 0.67x instead of 0.71x (or 0.726x for some competing focal reducers)?

Unfortunately not for a general-purpose APS-C reducer. If you imagine simply scaling up the XL to fit an APS-C sensor, then the problem is that the front element of the reducer will now crash into the rear element of most lenses.

Direct link | Posted on Jun 9, 2015 at 14:51 UTC
In reply to:

redeye47: I don't understand why XL doesn't work on all m43 mount cameras. Help me out here.

Micro four thirds cameras vary a lot in their mechanical design near the sensor. The GH4 and other Panasonic cameras permit a closer approach to the sensor with focal reducer optics, and this allowed a simultaeous increase in performance and reduction ratio.

Direct link | Posted on Jun 9, 2015 at 02:33 UTC
In reply to:

ShootFilmNotMegaPixels: So what would the result be for a f/1.0 lens after using this adapter?

With an f/1.2 attached lens you get f/0.80 output, which is the fastest now available for m4/3. If you use an f/1.0 lens such as the Canon 50mm f/1.0 then you still only get f/0.80 output due to the diameter of the front element of the Speed Booster.

Direct link | Posted on Jun 9, 2015 at 00:15 UTC
In reply to:

Wilight: Metabones, would you be so gentle to tell me what's the reason behind your prejudice against FUJI/Canon users?

"Metabones, would you be so gentle to tell me what's the reason behind your prejudice against FUJI/Canon users?"

There is absolutely zero prejudice going on here. Its all about technical difficulty and limited resources at a very small company. Reverse-engineering the Fuji electronic design is a pretty daunting task.

Direct link | Posted on Aug 30, 2014 at 22:02 UTC
On Sigma announces all-new 50mm F1.4 DG HSM 'Art' lens article (244 comments in total)
In reply to:

BobYIL: MTF curves indicate that this will be a better one than the 35mm Art. Remarkable!

Do you have a link to the MTF curves?

Thanks.

Direct link | Posted on Jan 7, 2014 at 04:38 UTC
In reply to:

dstanton: It's a good point the mechanical shutter would be in the way; but...

... I don't think all have mechanical shutters, All the MFT's I have; Pano and Oly -- the CCD is fully exposed. It's the newer models that recently came out where mechanical shutters are now in use.

But... who knows... I thought the same there -- wasn't there a standard for Micro Four Thirds -- for all to follow??

The Blackmagic cameras don't conform to any m4/3 standard (smaller sensor, 16:9 aspect ratio, no shutter, thinner filter stack, etc.). So its reasonable that these specialized Speed Boosters take full advantage of the unique opportunites presented by these cameras. Besides, there are several Speed Boosters that fit standard m4/3 cameras already.

Direct link | Posted on Dec 3, 2013 at 20:27 UTC
On First Impressions: Metabones Speed Booster article (354 comments in total)
In reply to:

parkmcgraw: The dark photos do not appear to be the result of Pixel Vignetting.

Condition statement, the iris aperture blades are located at an intermediary focal plane, hence not affecting the lens field of view.

The Speed Booster is an optical compressor. Hence, the last element is at a fixed distance from the focal plane. As such the solid angle field of view per pixel is also fixed.

Altering the lens aperture to the maximum open setting only alters the illumination intensity and not the solid angle cone of light at the detector (pixel).

Pixel vignetting, like film vignetting, being a non uniform field effect, the level of vignetting increases with off axis distance. The full field B&W test photos appearing uniform in illumination.

The dark photo and slight color shift looking like coating phase interference, visible as a drop in black levels on axis being minus the chromatic halo seen in the corner of the image field. The phase interference affecting the accuracy of the exposure meter.

No. The Speed Booster is designed to accept a maximum aperture of f/1.2 (actually f/(2^(1/3)) = f/1.2599) from the attached lens and then output a maximum aperture of f/0.90 to the camera.

The only possibility of clipping the on-axis ray bundle is if you attach a lens that is faster than f/1.2. The only SLR lens that meets this requirement is the Canon 50mm f/1.0. If you put that lens on the SB and open up to f/1.0 you won't get f/0.71 but rather only f/0.90 - the same as if you had attached an f/1.2 lens.

Direct link | Posted on Feb 23, 2013 at 04:05 UTC
On First Impressions: Metabones Speed Booster article (354 comments in total)
In reply to:

parkmcgraw: The dark photos do not appear to be the result of Pixel Vignetting.

Condition statement, the iris aperture blades are located at an intermediary focal plane, hence not affecting the lens field of view.

The Speed Booster is an optical compressor. Hence, the last element is at a fixed distance from the focal plane. As such the solid angle field of view per pixel is also fixed.

Altering the lens aperture to the maximum open setting only alters the illumination intensity and not the solid angle cone of light at the detector (pixel).

Pixel vignetting, like film vignetting, being a non uniform field effect, the level of vignetting increases with off axis distance. The full field B&W test photos appearing uniform in illumination.

The dark photo and slight color shift looking like coating phase interference, visible as a drop in black levels on axis being minus the chromatic halo seen in the corner of the image field. The phase interference affecting the accuracy of the exposure meter.

Pixel vignetting, which I call sensor-induced apodization, occurs everywhere in the image, including the center of the field. Its all about marginal ray angle and the reduced sensor sensitivity as the angle of incidence increases.

At f/2 the marginal rays on-axis strike the sensor at 14.5 degrees, which most sensors handle very well. At f/1 the marginal ray angle increases to 30 degrees, which causes significant signal reduction with most sensors. At f/0.7 the marginal ray angle is 45 degrees which. Remenber, this is for the center of the image, and has nothing to do with field-dependent falloff.

So, opening up a lens from f/2 to f/1 will not give you four times as much signal from the sensor. This is purely a sensor effect and has nothing to do with the optics.

Direct link | Posted on Feb 17, 2013 at 05:00 UTC
On First Impressions: Metabones Speed Booster article (354 comments in total)
In reply to:

Salvador Abreu: Interesting, this is in essence what Nikon (& Fuji) did with back in 1995 (!!) with the Nikon E2 and E3 (aka Fujix DS-560 and Fujix DS-565) - see http://en.wikipedia.org/wiki/Nikon_E_series for more details.

Now what I'd really like to see is a Nikon F-mount adapter like this with add-on AF, for use with MF lenses, a bit like the TC-16a. That would be mighty useful on DX bodies...

Salvador:
Any similarity between the Nikon E system and the Speed Booster is superficial at best.

The wikipedia article leaves out several critical details that ultimately doomed the Nikon E series. True, it used an image reduction system, but it was a relay type located entirely behind the normal image produced by the objective lens. I call this a Keplerian type reducer. As a result, it added a huge amount of bulk to the system. The lens aperture was limited to f/6.7 in early E versions and f/4.8 in the last version. In other words, even if you used an f/1.4 lens, if you opened it up wider than f/4.8 (or f/6.7 in the earlier versions) the exposure and depth of field would not change.

By contrast, the Speed Booster is a Galilean type reducer that fits between the objective lens and the image plane. The Speed Booster actually reduces the system length and bulk, and is also fully usable with f/1.2 objecttives, which means you can take full advantage of a shallow depth of field.

Direct link | Posted on Feb 3, 2013 at 16:14 UTC
On First Impressions: Metabones Speed Booster article (354 comments in total)
In reply to:

Krich13: Could you please clarify the testing procedure? When the Canon lens is tested at say f/1.4 with Speed Booster, is the "boosting" effect already taken into account? In other words, is the lens itself stopped down to f/2, and "becomes" f/1.4 using the adapter? Or is it used wide-open at f/1.4 and effectively turns f/1 with the adapter? Later in the review you discuss the 40 mm lens at f/2, so it seems that the effect of the adapter is taken into account, I just want to be sure.

The same question about the f/8 test. Are both _lenses_ set to f/8 or both _systems_ (including the adapter) set to f/8?

Thank you in advance

According to metadata for the wide-open test chart image (as reported in Photoshop) the focal length is 35mm and the aperture is f/1.0. So I assume that at least for this comparison we are looking at f/1.0 vs. f/1.4.

Direct link | Posted on Feb 1, 2013 at 21:14 UTC
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