# Calling owners of the Canon FD 85mm 1.2L on Speedboosters

Started Apr 22, 2014 | Discussions
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Calling owners of the Canon FD 85mm 1.2L on Speedboosters

Owners of the Canon FD 85mm 1.2L on a Speedbooster, any comments?

Just been performing some camera math on the Canon FD 85mm f/1.2L as I hear this lens it very sharp wide open. Is this true?

If so, mounting this on a Speedbooster should create a 60mm lens which in theory translates into a lens with a 'full frame equivalent' of a 120mm f/2.4 but with light gathering ability of an f/0.85! (Maths below)

Given the maths, the price of this lens secondhand seems be reasonable compared to the Voigtlander f/0.95 series.

PHOTOGRAPHY MATHS :
(Tell me if I've made any errors!)

Camera Math Sources: Tony Northrup / Petapixel and Metabones Speedbooster White Paper

1. ORIGINAL LENS
Focal Length: 85mm (Field of view 85mm)
F-Stop: f/1.2 (Light gathering ability f/1.2)
2. LENS MOUNTED ON SPEEDBOOSTER
Multiply focal length and FoV by factor of x 0.71, reduce light gathering ability by 1-stop
Focal Length: 60mm (Field of view 60mm)
F-Stop: f/1.2 (Light gathering ability f/0.85)
3. LENS MOUNTED ON SPEEDBOOSTER ON AN MFT SENSOR
Multiple field of view AND f-stop by crop factor of x 2
Focal Length: 60mm (Field of view 120mm)
F-Stop: f/2.4 (Light gathering ability f/0.85)
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Re: Calling owners of the Canon FD 85mm 1.2L on Speedboosters

wilkes888 wrote:

Owners of the Canon FD 85mm 1.2L on a Speedbooster, any comments?

Just been performing some camera math on the Canon FD 85mm f/1.2L as I hear this lens it very sharp wide open. Is this true?

If so, mounting this on a Speedbooster should create a 60mm lens which in theory translates into a lens with a 'full frame equivalent' of a 120mm f/2.4 but with light gathering ability of an f/0.85! (Maths below)

Given the maths, the price of this lens secondhand seems be reasonable compared to the Voigtlander f/0.95 series.

PHOTOGRAPHY MATHS : (Tell me if I've made any errors!)

Camera Math Sources: Tony Northrup / Petapixel and Metabones Speedbooster White Paper

1. ORIGINAL LENS
Focal Length: 85mm (Field of view 85mm)
F-Stop: f/1.2 (Light gathering ability f/1.2)
2. LENS MOUNTED ON SPEEDBOOSTER
Multiply focal length and FoV by factor of x 0.71, reduce light gathering ability by 1-stop
Focal Length: 60mm (Field of view 60mm)
F-Stop: f/1.2 (Light gathering ability f/0.85)
3. LENS MOUNTED ON SPEEDBOOSTER ON AN MFT SENSOR
Multiple field of view AND f-stop by crop factor of x 2
Focal Length: 60mm (Field of view 120mm)
F-Stop: f/2.4 (Light gathering ability f/0.85)

Provided that the speedbooster works as it should with this ultrafast lens (which I don't know), the combo will be f/0.85 (1.2 x 0.71) with regard to exposure. With regard to light gathering ability, DoF, and diffraction, however, it will be equivalent to f/1.7 (2 x 0.85) on FF. As you have correctly calculated, the FL will be 60 mm, equivalent to 120 mm on FF.

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Re: Calling owners of the Canon FD 85mm 1.2L on Speedboosters

Anders W wrote:

With regard to light gathering ability, DoF, and diffraction, however, it will be equivalent to f/1.7 (2 x 0.85) on FF.

I'm now confused... the Metabones FAQ page states the following...

Source: Metabones FAQ

What have I misunderstood? Between the white paper and the FAQ I interpreted the depth of field (and therefore the f-number) to actually remain unchanged so I multiplied the f/1.4 by 2.

Admittedly the FAQ continues with the following which clouds the issue... but seems to conclude the same.

Source: Metabones FAQ

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Re: Calling owners of the Canon FD 85mm 1.2L on Speedboosters

Unfortunately, I converted my FDn 85mm f/1.2L to EF with an EdMika kit. It's reversable, but extremely difficult, complex and not worth my time, so I'm stuck waiting with my 85mm f/1.2 for the promised EF-MFT speedbooster...

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--Mike

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Re: Calling owners of the Canon FD 85mm 1.2L on Speedboosters

wilkes888 wrote:

Anders W wrote:

With regard to light gathering ability, DoF, and diffraction, however, it will be equivalent to f/1.7 (2 x 0.85) on FF.

I'm now confused... the Metabones FAQ page states the following...

Source: Metabones FAQ

What have I misunderstood? Between the white paper and the FAQ I interpreted the depth of field (and therefore the f-number) to actually remain unchanged so I multiplied the f/1.4 by 2.

Admittedly the FAQ continues with the following which clouds the issue... but seems to conclude the same.

The field of view is approximately the same when used on a larger APS-C sensor, not on the smaller m4/3 sensor.

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A photograph is a creative interpretation of reality.

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Re: Calling owners of the Canon FD 85mm 1.2L on Speedboosters

wilkes888 wrote:

Anders W wrote:

With regard to light gathering ability, DoF, and diffraction, however, it will be equivalent to f/1.7 (2 x 0.85) on FF.

I'm now confused... the Metabones FAQ page states the following...

Source: Metabones FAQ

What have I misunderstood?

Between the white paper and the FAQ I interpreted the depth of field (and therefore the f-number) to actually remain unchanged so I multiplied the f/1.4 by 2.

Admittedly the FAQ continues with the following which clouds the issue... but seems to conclude the same.

What they forgot to mention in the FAQ is that they are talking about what happens when you put an FF lens with the Speed Booster on an APS-C camera. You want to put it on an MFT camera. In that case, the statement of mine that you quoted above applies.

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Re: Calling owners of the Canon FD 85mm 1.2L on Speedboosters
2

wilkes888 wrote:

Owners of the Canon FD 85mm 1.2L on a Speedbooster, any comments?

Just been performing some camera math on the Canon FD 85mm f/1.2L as I hear this lens it very sharp wide open. Is this true?

If so, mounting this on a Speedbooster should create a 60mm lens which in theory translates into a lens with a 'full frame equivalent' of a 120mm f/2.4 but with light gathering ability of an f/0.85! (Maths below)

Given the maths, the price of this lens secondhand seems be reasonable compared to the Voigtlander f/0.95 series.

PHOTOGRAPHY MATHS : (Tell me if I've made any errors!)

Camera Math Sources: Tony Northrup / Petapixel and Metabones Speedbooster White Paper

1. ORIGINAL LENS
Focal Length: 85mm (Field of view 85mm)
F-Stop: f/1.2 (Light gathering ability f/1.2)
2. LENS MOUNTED ON SPEEDBOOSTER
Multiply focal length and FoV by factor of x 0.71, reduce light gathering ability by 1-stop
Focal Length: 60mm (Field of view 60mm)
F-Stop: f/1.2 (Light gathering ability f/0.85)
3. LENS MOUNTED ON SPEEDBOOSTER ON AN MFT SENSOR
Multiple field of view AND f-stop by crop factor of x 2
Focal Length: 60mm (Field of view 120mm)
F-Stop: f/2.4 (Light gathering ability f/0.85)
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First of all, AFAIK, all photographic lenses marked as "f/1.2" are actually 1/3 stop faster than f/1.4, meaning that they are really f/(2^(1/3)) = f/1.2599.

When you attach the 0.71x Speed Booster to an 85mm f/1.2599 lens  you create a 60.4mm f/0.9 lens.  Forget all the crop factor and light gathering ability stuff.  Consider this:  if Panasonic or Olympus developed a 60.4mm f/0.9 lens for micro four thirds, do you really think they would market it as a 120mm f/1.8?

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Brian Caldwell

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Re: Calling owners of the Canon FD 85mm 1.2L on Speedboosters

brian wrote:

wilkes888 wrote:

Owners of the Canon FD 85mm 1.2L on a Speedbooster, any comments?

Just been performing some camera math on the Canon FD 85mm f/1.2L as I hear this lens it very sharp wide open. Is this true?

If so, mounting this on a Speedbooster should create a 60mm lens which in theory translates into a lens with a 'full frame equivalent' of a 120mm f/2.4 but with light gathering ability of an f/0.85! (Maths below)

Given the maths, the price of this lens secondhand seems be reasonable compared to the Voigtlander f/0.95 series.

PHOTOGRAPHY MATHS : (Tell me if I've made any errors!)

Camera Math Sources: Tony Northrup / Petapixel and Metabones Speedbooster White Paper

1. ORIGINAL LENS
Focal Length: 85mm (Field of view 85mm)
F-Stop: f/1.2 (Light gathering ability f/1.2)
2. LENS MOUNTED ON SPEEDBOOSTER
Multiply focal length and FoV by factor of x 0.71, reduce light gathering ability by 1-stop
Focal Length: 60mm (Field of view 60mm)
F-Stop: f/1.2 (Light gathering ability f/0.85)
3. LENS MOUNTED ON SPEEDBOOSTER ON AN MFT SENSOR
Multiple field of view AND f-stop by crop factor of x 2
Focal Length: 60mm (Field of view 120mm)
F-Stop: f/2.4 (Light gathering ability f/0.85)
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First of all, AFAIK, all photographic lenses marked as "f/1.2" are actually 1/3 stop faster than f/1.4, meaning that they are really f/(2^(1/3)) = f/1.2599.

When you attach the 0.71x Speed Booster to an 85mm f/1.2599 lens you create a 60.4mm f/0.9 lens. Forget all the crop factor and light gathering ability stuff. Consider this: if Panasonic or Olympus developed a 60.4mm f/0.9 lens for micro four thirds, do you really think they would market it as a 120mm f/1.8?

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Brian Caldwell

I doubt that all 1.2 lenses ARE 1.2......just as with lots of lenses (most probably) they are not exact and are often rounded up/down.

I can live with them being 1.2

Must get a speedbooster/focal reducer for my three 1.2 lenses some time.

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Re: Calling owners of the Canon FD 85mm 1.2L on Speedboosters

neil holmes wrote:

I doubt that all 1.2 lenses ARE 1.2......just as with lots of lenses (most probably) they are not exact and are often rounded up/down.

Well, mathematically, if a lens was designed to be 1/2 of a stop faster than a f/1.4 it will be a f/1.1892 (i.e. 1/SQRT(0.5)^0.5). So yes it is rounded up. But I don't know if the lens designers worked to that spec.

Must get a speedbooster/focal reducer for my three 1.2 lenses some time.

I have a cheap focal reducer which gives a nice angle of view for my FD 50mm f/1.4 on a MFT but it seems to have degraded the quality compared to the plain adaptor with no optics. I didn't notice it at first as it's not immediately obvious so it's not terrible.

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brian wrote:

First of all, AFAIK, all photographic lenses marked as "f/1.2" are actually 1/3 stop faster than f/1.4, meaning that they are really f/(2^(1/3)) = f/1.2599.

Good point... but wouldn't it would make more sense if the f/1.2 was actually 1/2 of a stop faster than a f/1.4? That would make it an f/1.1892 (i.e. 1/SQRT(0.5)^0.5). If what you say is correct that would be very misleading from Canon.

... if Panasonic or Olympus developed a 60.4mm f/0.9 lens for micro four thirds, do you really think they would market it as a 120mm f/1.8?

I agree, as Tony Northrup says in his video (at the end) the manufacturers don't market a MFT f/0.9 lens as a f/1.8 because it doesn't sound as good.

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Elemental Photography wrote:

The field of view is approximately the same when used on a larger APS-C sensor, not on the smaller m4/3 sensor.

That makes a lot more sense... thanks for that... I thought something wasn't quite right!

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Anders W wrote:

What they forgot to mention in the FAQ is that they are talking about what happens when you put an FF lens with the Speed Booster on an APS-C camera. You want to put it on an MFT camera. In that case, the statement of mine that you quoted above applies.

Thanks for enlightening me... that makes a lot more sense!

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MAubrey wrote:

Unfortunately, I converted my FDn 85mm f/1.2L to EF with an EdMika kit. It's reversable, but extremely difficult, complex and not worth my time, so I'm stuck waiting with my 85mm f/1.2 for the promised EF-MFT speedbooster...

Damn, not good

Do you have any shots I could look at taken with your FD 85mm f/1.2? Curious to see what the 'un-Speedboost-ed' images are like...

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wilkes888 wrote:

I agree, as Tony Northrup says in his video (at the end) the manufacturers don't market a MFT f/0.9 lens as a f/1.8 because it doesn't sound as good.

A µ4/3 f/0.9 lens is not called f/1.8 because doing so would be lying. Also note that full frame lens manufacturers do not call a f/2.0 lens a f/1.0 lens, because it would be lying, too.

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Re: Calling owners of the Canon FD 85mm 1.2L on Speedboosters

I don't disagree, but watch the last section of the video where Tony asks manufacturers to make things clearer on lens specifications.

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wilkes888 wrote:

I don't disagree, but watch the last section of the video where Tony asks manufacturers to make things clearer on lens specifications.

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Focal length and f/# have clear and unambiguous meanings that have nothing to do with format size.  An f/0.9 lens should never be marketed as an f/1.8 lens because its f/0.9, not f/1.8.  The marginal ray angles are completely different, as can easily be verified on an optical bench.

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Brian Caldwell

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Re: Calling owners of the Canon FD 85mm 1.2L on Speedboosters
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wilkes888 wrote:

brian wrote:

First of all, AFAIK, all photographic lenses marked as "f/1.2" are actually 1/3 stop faster than f/1.4, meaning that they are really f/(2^(1/3)) = f/1.2599.

Good point... but wouldn't it would make more sense if the f/1.2 was actually 1/2 of a stop faster than a f/1.4? That would make it an f/1.1892 (i.e. 1/SQRT(0.5)^0.5). If what you say is correct that would be very misleading from Canon.

It might seemingly make more sense, but its not ever done in the industry AFAIK.

... if Panasonic or Olympus developed a 60.4mm f/0.9 lens for micro four thirds, do you really think they would market it as a 120mm f/1.8?

I agree, as Tony Northrup says in his video (at the end) the manufacturers don't market a MFT f/0.9 lens as a f/1.8 because it doesn't sound as good.

Will have to check out this video later, but to be honest it sounds like Tony is way off base here.

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Brian Caldwell

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wilkes888 wrote:

Do you have any shots I could look at taken with your FD 85mm f/1.2? Curious to see what the 'un-Speedboost-ed' images are like...

Here are a few...nothing formal though.

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--Mike

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Anders W wrote:

wilkes888 wrote:

Owners of the Canon FD 85mm 1.2L on a Speedbooster, any comments?

Just been performing some camera math on the Canon FD 85mm f/1.2L as I hear this lens it very sharp wide open. Is this true?

If so, mounting this on a Speedbooster should create a 60mm lens which in theory translates into a lens with a 'full frame equivalent' of a 120mm f/2.4 but with light gathering ability of an f/0.85! (Maths below)

Given the maths, the price of this lens secondhand seems be reasonable compared to the Voigtlander f/0.95 series.

PHOTOGRAPHY MATHS : (Tell me if I've made any errors!)

Camera Math Sources: Tony Northrup / Petapixel and Metabones Speedbooster White Paper

1. ORIGINAL LENS
Focal Length: 85mm (Field of view 85mm)
F-Stop: f/1.2 (Light gathering ability f/1.2)
2. LENS MOUNTED ON SPEEDBOOSTER
Multiply focal length and FoV by factor of x 0.71, reduce light gathering ability by 1-stop
Focal Length: 60mm (Field of view 60mm)
F-Stop: f/1.2 (Light gathering ability f/0.85)
3. LENS MOUNTED ON SPEEDBOOSTER ON AN MFT SENSOR
Multiple field of view AND f-stop by crop factor of x 2
Focal Length: 60mm (Field of view 120mm)
F-Stop: f/2.4 (Light gathering ability f/0.85)

Provided that the speedbooster works as it should with this ultrafast lens (which I don't know), the combo will be f/0.85 (1.2 x 0.71) with regard to exposure. With regard to light gathering ability, DoF, and diffraction, however, it will be equivalent to f/1.7 (2 x 0.85) on FF. As you have correctly calculated, the FL will be 60 mm, equivalent to 120 mm on FF.

I am reasonably sure that all focal reducers are limited to a maximum light gathering ability of f/0.90 no matter what lens is fitted.  No small thing nevertheless.

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Tom Caldwell

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wilkes888 wrote:

Anders W wrote:

With regard to light gathering ability, DoF, and diffraction, however, it will be equivalent to f/1.7 (2 x 0.85) on FF.

I'm now confused... the Metabones FAQ page states the following...

Source: Metabones FAQ

What have I misunderstood? Between the white paper and the FAQ I interpreted the depth of field (and therefore the f-number) to actually remain unchanged so I multiplied the f/1.4 by 2.

Admittedly the FAQ continues with the following which clouds the issue... but seems to conclude the same.

Source: Metabones FAQ

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I suggest that you stop working yourself into a lather - buy the durn thing, you will be pleased and with the FD 85/1.2 you will get cheap gym fees - it is a big lens

Oh - and remember focus peaking is your friend.

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Tom Caldwell

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