Glass and mounts for fs100
 

I would like to know your thoughts. I heard Carl is adapting a lens package to fit the emount. I assume those irises will be controled by a ring on the lens vs the sony iris dial.

But what lens/mounts/adapters/ ND will you use?

Are you the type of shooter that wants to adapt your existing package from canon or Nikon vs investing in new glass? If so how?

Re: Glass and mounts for fs100
 

I spent some time on the Birger Mount stand during NAB 2011. The upcoming adapter for Canon EOS lenses looks very promissing. This adapter will be released around the time the FS-100 will be available (July/August), but there can of course be delays. Having a large collection of Canon L lenses I'll prefer to use
the Birger Mount to utilize these lenses. Adding the Birger Mount remote control I can even have automated focusing on the EOS lenses.

Best,
-terje

Re: Glass and mounts for fs100
 

Thanks for that info. I watched the video about the Birger mount. That is an impressive product. I have canon ef mount lenses as well. Your post happened to be exactly what I was looking for. So long as the Birger mount with fallow focus is affordable, it is the perfect solution. Iris and focus control, its programable too. Very cool.

The only con: is no hard stops on the fallow focus. I would also like some sort of way to mount it to the handles on my over the shoulder rig, tripod handle or steadicam. Sometimes I don't have the luxury of a focus puller.

The company needs to work on their site, I could not find a store or pricing info.

I agree it is a game changer. I am hoping that they fallow in the footsteps of companies like Atomos or Decklink and make this product exponentially cheaper than their competitors.

Some of these companies are off their rockers charging 5-10k for similar remote focus/ iris pulling products. If they want to sell in volume and put one in everyones hands make it a lot cheaper than the cameras we put it on.

It seems that most of us when faced with purchasing an add on that is more expensive than the camera aside from glass, we often decide to spend that money on a 2nd camera. The logic is. Yes I can get that add on but for that price I can have a B camera.

Re: Glass and mounts for fs100
 

Hello Jason,

I just found a link to an interview with Erik Widding, the owner of Birger Engineering, from NAB 2011. The clip might me intersting for you...?

NAB 2011 - Birger engineering Canon EOS to AF100 to Sony NEX adapter - Sony NEX-FS100 Super 35mm User Group on Vimeo

Best,
-terje

Re: Glass and mounts for fs100
 

I already have a wide range of Nikon lenses so I will be using those initially, however the Birger mount with remote focus is very attractive.

Re: Glass and mounts for fs100
 

Wow I am so excited about this product. I like that he mentioned that it would be inexpensive. I hope they move forward quickly with the Sony fs100 I have no interest in the smaller sensor on the af100.

It was kind of unclear if the unit for the sony fs100 would also be available as a remote fallow focus and not tethered like the remote fallow focus unit shown with the af100.

Erik Widding from Birger was very knowledgeable he did a great job with his demo in the video I would love to ask him additional specific questions.

ONLY $700.00 for the mount and additional $500-$700.00 for the remote fallow focus.
O my GOD!!!

I can't hardly wait. It was not clear to me when both the mount and fallow focus will be available for the FS100

My only concern is that because the mount pushes the lens that much further away from the sensor, is there going to be a significant increase in depth of field, in effect giving less of the shallow depth of field look.

My thought is that depth of field is derived from the ratio of the size of the sensor to the lens and how wide the iris can open. AKA how fast the lens is.

So comparatively if you had a sony alpha emount lens that was about f1.8 vs a canon lens that is f1.8 would the canon have more depth of field because of the birger mount pushing the lens away from the sensor making it in a sense smaller?

Re: Glass and mounts for fs100
 

The Birger mount does not "Push the lens further from the sensor". If it did you would not be able to focus the lens. The necessary distance from the rear of the lens to the sensor (flange back) is fixed by the lens design. The Birger is no different to any other adapter in this respect so there is no change to FoV or DoF.

DoF is a function of aperture and focal length. So a 50mm lens at f1.8 will have the same DoF as any other 50mm lens at f1.8, whether its, Nikon, Canon or Sony. The flange back distance makes no difference.

Re: Glass and mounts for fs100
 

Thanks for heling me understand that about the mount. I am going to have to add some additional info to your statement on DOF. The larger the sensor the shallower the capability DOF.

In other words the canon 5D gives a shallower depth of field than a Canon 60D even if both cameras have the same lens, focal length, and aperture. Why? Because the sensor on the 5D is larger. This is one of the important contributing factors on why cameras with tiny 1/4 inch sensors dont easily give shallow DOF.

The details you mentioned above are the other contributing factores.

Re: Glass and mounts for fs100
 

Actually technically that's incorrect - if both cameras have the same lens, focal length and aperture then the DOF will be exactly the same. The field of view won't be the same though - the 60D will appear zoomed in closer than the 5D. Thus, if you use lenses of different focal lengths to achieve the same field of view between both cameras, or move the 60d farther away from the subject so that the shots match, you will end up with slightly deeper depth of field on the 60D. 1/4 inch sensors don't easily give shallow DOF because you have to use extremely short focal lengths to achieve even 'normal' shot compositions - in the 4-6mm range. Put a 4mm lens on a 5D ( if you could find one!) and you'll get the same deep DOF as a 1/4" camera but the shot will appear much wider.

Re: Glass and mounts for fs100
 

I appreciate where you'r coming from and part of me agrees but the proof is in the pudding and because of the size of the 5D sensor and its ratio to lens we are in uncharted territory its extremely rare to get that type of fall off in the focus or DOF.

Remember those adapters for video cameras like the p+s technik's adapter?

That allowed you to achieve a shallow depth of field in part because the image projected on the rotating ground glass was considerably larger than the sensor of the video camera. This was intensional. Additionaly attaching a fast lens with a 1.8 F stop helps as well.

Re: Glass and mounts for fs100
 

I suspect the DOF is pretty much the same, but the angle of view is different - which would mean you'd move in closer to maintain the subject size relative the frame (the image is larger on the 5D), so you're changing the distance. That's the case with 16mm v 35mm motion picture when you check the DOF tables for the same focal length at the same distance. It's commonly a particular an angle of view which is the deciding factor in selecting a lens for a shot.

Birger is quoting "MSRP $700" for their AF100 adapter, which is pretty similar to the price they quoted for the RED version.

Re: Glass and mounts for fs100
 

I have a question regarding compatible lenses:

B&H lists some lenses that "aren't compatible with 35mm or full-frame digital SLRs."
Can these be used with a Super 35 sensor?

Re: Glass and mounts for fs100
 

That would be possible Glenn.

The problem with the EF-S lenses is they protrude deeper into the body and on the full frame cameras cause some physical interference problems as well as not optically covering the sensor.

Since the imager in the FS100 is similar in size to the APC sensor used in still cameras it would be optically compatible. We have to see if its going to be physically compatible. Since the FS100 doesn't have a ND filter on top of the imager the flange-back distance may work out.

Re: Glass and mounts for fs100
 

Yes. Every normal SLR lens will cover the sensor.

Re: Glass and mounts for fs100
 

I stand corrected and fall on y sword.

Re: Glass and mounts for fs100
 

An important observation from the test shoot that I did with Den Lennie earlier in the week is that if you are using a lens adapter, we used a cheap e mount to nikon. If you are going to use full frame lenses then it is vital that the adapter incorporates a choke or baffle. Without one you will get some strange flare characteristics. The MTF adapters do have a baffle, I wish we had used one of those and not the cheaper one that we had.

Re: Glass and mounts for fs100
 

Alister,

Thanks for the tip. But would you mind explaining what a "choke" or a "baffle" is (when it comes to an adapter)? My dictionary isn't very helpful, I'm afraid. I need to know what to look for, if I decide to purchase an adapter. Thank you!

Best,
-terje

Re: Glass and mounts for fs100
 

We should ask Birger if they have a choke or baffle for their mount.

Re: Glass and mounts for fs100
 

So what lenses do you buy to get iris & semi auto focus enabled? I would love to get this camera but I have no idea what F2.8 lenses will work on this body (electronically).

Re: Glass and mounts for fs100
 

Dear Alister,

Please explain to us mortals what a choke or baffle is (preferably with a picture of an adapter).

Thanks

Piotr

Re: Glass and mounts for fs100
 

PMJI (oops, Pardon My Jumping In) before Alister got a shot, but you know what waiting for uploads can be like...

The choke or baffle Alister refers to would be a simple aperture within the mount to restrict the amount of light going through it, a bit like an 'internal matte box' for the adaptor. Lenses designed to shine their light onto huge great big Full Frame sensor would tend to shine their light over the internal bits around the edges of the smaller S35 sensor, thus perhaps causing internal reflections or glare. By blocking out around the edges and leaving just the middle bit, the stray light absorbed by matte black surfaces, you'll get more contrast, deeper blacks, all that expensive meaty goodness.

Returning you now to your scheduled programming...

Re: Glass and mounts for fs100
 

I am sure the Birger mount will have something like that in mind.

Re: Glass and mounts for fs100
 

Thanks Matt - got the idea.

Being a mechanical engineer, I couldn't help associating those two names with mechanical "features" I am familiar with (e.g. a "baffle" is a special element of plastic injection mold for cooling narrow and deep cores). Realizing of course we're talking optics here (and not mechanics), I wasn't able to guess without a right hint like the one from you :)

Piotr

Re: Glass and mounts for fs100
 

You can use Sony A-mount lenses with the Sony adaptor LA-EA1.
The Zeiss / Sony SAL2470Z is 24-70mm f2,8. this will give you a focal lenght of around 36 - 105mm on the FS100.

Re: Glass and mounts for fs100
 

The focal length doesn't change, it's an equivalent focal length that gives the same angle of view on the different sensor. I suspect people know what you mean, but it can become confusing.

Re: Glass and mounts for fs100
 

Thanks that's what I was hoping for, I currently own Canon glass but I'll easily trade them in for Sony glass if it means I can get them to work electronically with the FS-100. Do you know if you lose any light with this adapter?

Re: Glass and mounts for fs100
 

Thanks Brian for correcting me. Of course, a given focal length is always the same.
On a 50mm lens the distance to the focal plane is always 50mm no matter how large or small a sensor the camera it is mounted on has.
I always think of the angle since it is the important thing to get the entire scene framed. Now we're at it, we can also affirm that DOF is always the same with the same focal length as a 50mm lens with a given aperture always gives the same DOF. It is the focal length you need to frame your scene you change and an efekt of that you also changes the DOF.


Nicholas, adapters for different lenses do not contain any optical elements so there is no light loss.

Re: Glass and mounts for fs100
 

BBC TV studio directors and TV studio camera operators used to be trained in angles of view rather than the focal length. In practise that makes a lot of sense when planing and framing shots.

Re: Glass and mounts for fs100
 

[QUOTE=Brian Bang Jensen;1647584On a 50mm lens the distance to the focal plane is always 50mm no matter how large or small a sensor the camera it is mounted on has.[/QUOTE]

That's not quite correct. The focal length is the amount that the lens converges light or the optical power of the lens.

The distance between the rear of the lens and the sensor, known as the flange back will vary depending on the design of the camera. On a Canon EF-S camera it is 44mm on a Nikon it is 46.5 and E-Mount is 18mm. That's why you can put a Nikon lens on a Canon or Sony, but not the other way around. A 50mm lens will always be a 50mm lens no matter whether it has a 18mm flange back or 44mm flange back. If you try to use a lens at the wrong distance from the sensor you won't be able to focus it (or at least the focus scale will be off).

It's all very confusing, particularly because people often talk about applying a conversion factor to the lens when really the conversion factor should be though of as applying to the camera as it is the camera and the size of it's sensor that changes, not the lens.

Re: Glass and mounts for fs100
 

For clarity, that's not quite right.

DOF is is a function of focal length and the aperture, but is also determined by the camera-to-subject distance and the format size or circle of confusion.

You are right that using adapters won't affect focal length, but altering the flange back can affect infinity focus.

Re: Glass and mounts for fs100
 

Normally, I think you are very knowledgeable but at this point I partly disagree.
A lens focal length is equal to the distance from film plane to the theoretical focal point inside the lens.The focal point is the point where the light crosses inside lens.FB is the distance to be adjusted to achieve the right focus length for the lens, thus putting the lens in focus. But maybe we mean the same thing and it is language difficulty that separates us :-)

Re: Glass and mounts for fs100
 

Perhaps this covers the definition

Flange focal distance - Wikipedia, the free encyclopedia

Often called the flange distance.

Re: Glass and mounts for fs100
 

And this.

Focal length - Wikipedia, the free encyclopedia

I can see that we just use different expressions to describe the same topic.

Re: Glass and mounts for fs100
 

OK, optics are not my forte but according to my understanding the focal point is where collimated light that passes through a single lens is focussed and it will be some distance behind the lens. See Focal point - Wikipedia, the free encyclopedia

For a single convex element in air it is true that this distance, from the lens vertex (center) to focal point is the focal length. The focal plane would normally pass through the focal point and the sensor or film would be placed at the focal plane. But we are not talking about single element convex lenses, we are talking about multi-element camera lenses and this is probably where our confusion with each other comes in.

With camera lenses it becomes very complicated, especially with wide angle lenses.
In your earlier post Brian you said that "On a 50mm lens the distance to the focal plane is always 50mm". My interpretation of that is that you are saying that there would be 50mm from the center of the lens to the focal plane, i.e. where the film or sensor is placed. That is fine in theory, but it implies that 300mm lens has to be 300mm from the sensor and what about zoom lenses with a variable focal length? In practice it's obvious that this is not normally the case and this is confirmed by the table provided by Brian.

How for example do you get a 16mm lens to work on a camera with a lens to focal plane distance greater than 18mm (Sony NEX) or even 44mm (Canon DSLR)? How can you get the focal plane behind the focal point? Well it's done using multiple lens elements (wide retrofocus lens) and it's one of the reasons why good wide angle lenses are so expensive and demonstrates how the indicated focal length is not the actual focal length but a theoretical one know as the "effective focal length". Most stills and video lenses give their EFL (effective focal length) as opposed to the true focal length and it is calculated according to the magnifying power of the lens. See Camera lens - Wikipedia, the free encyclopedia

So IMHO the confusion stems from the fact that when a camera manufacturer gives the focal length of a lens it is a calculated equivalent distance based on the lenses magnification and not the actual focal length.

I think we all agree that a 50mm lens is a 50mm lens, no matter what size the sensor it is still a 50mm lens.
That you can have almost any flange back distance i.e. distance from lens rear to the sensor or film plane. This is determined by the camera manufacturer.
That the flange back distance does not change the focal length and you can have a 50mm lens that is only 18mm from the sensor, or 44mm or 46mm etc.
The focal length determines the magnification factor of the lens.
It is the size of the sensor that determines the FOV, not the flange back distance or any other factor.

Re: Glass and mounts for fs100
 

Alister I totally agree.
It is the theoretically focal length. I forgot the word “theoretically” in my post, my mistake.

Regarding wide lenses, before retrofocus where implemented in the design, the lenses actually protruded far into the camera and the mirror had to bee locked in the upper position, preventing it to hit the rear of the lens and a long lens were actually a drain pipe..