Relay lens for 1/2" AND 2/3" sensors (for Dof adapters)

M

Marshallarts

Well-known member
I recently started this thread inquiring about current options for a B4 mount relay lens for a 35mm DoF adapter. I received some great feedback and learned of other related threads (that didn't show up in my initial search of the forums).

I applaud Cinevate for what I learned from Dennis Wood's reply. He states they are coming out with a B4 mount Relay lens, as is Letus, but Cinevate's will be the first "multi-format" relay lens with a FoV for BOTH 35mm & Cine (APS) lenses on a DoF adapter (through the use of an internal zoom inside the Relay). I'm not sure how that will effect sharpness, CA, and the many other possible issues that could arise given the technicalities and sensitivity of the optics involved, but I applaud their innovation (or Cinevation!).

It got me thinking. I have a question I would like to ask. The optics involved for this is beyond my grasp but I'm very eager to understand and learn:

Is it possible to create a "Quality" relay lens for use on BOTH a 1/2" & 2/3" camera. I know the mounts are different, but that's the easiest obstacle. What are the technical problems that can arise for this type of venture? Admittedly I don't know how a relay lens operates. I would like to know if this is possible. And if not please explain how these operate.

Use it on a EX3 & a F900!
 
You can use a 2/3 to 1/2 inch converter on all relay mounts being released soon. Cinevates and Letus's. The problem is optimizing a lens. These lenses will be specifically optimized for the adapters they are meant to work with. Meaning while you can use another adapter, it'd probably be advised against.
 
here's another question. Why not just use a 16mm zoom lens(or the fixed scarlet;s zoom) instead of a relay? I'm not quite grasping the advantages of a relay...
 
Astigmatic- what we want is the DoF you get with 35mm. You need a DoF adapter to obtain this because you need to create a new field of view, doable by projecting the image onto a ground glass inside the Dof adapter then shootig that. A 16mm lens will still only yield a much larger depth of field. Read some depth of field charts to see what I mean. You can iris open but still the difference between 35academy and 16 is great

Joseph-
Joseph Stunzi said:
You can use a 2/3 to 1/2 inch converter on all relay mounts being released soon. Cinevates and Letus's. The problem is optimizing a lens. These lenses will be specifically optimized for the adapters they are meant to work with. Meaning while you can use another adapter, it'd probably be advised against.
Click to expand...

Do you mean optimizing the lens for it's primary intended FoV? I would think given the optic flange distances being different that would have a greater effect on MTF and such. Or are you saying optimized between manufacturers of the DoF adapter? I would only plan to buy one anyhow.
 
Marshallarts said:
A 16mm lens will still only yield a much larger depth of field. Read some depth of field charts to see what I mean. You can iris open but still the difference between 35academy and 16 is great
Click to expand...

To clarify, a 16mm lens yields the same DOF and FOV as it's 35mm focal length equivalent, but if you have a smaller sensor, you can only "see" a small part of that projected image, resulting in a telephoto image on a wide lens. Just to throw out random numbers a 50mm lens might look like a 100mm. The reason we say that video camera have longer DOF is because manufacturers use lenses with extremely wide FOV (like 4mm etc.) so when you crop that off you end up with something like 33mm on 1/3'' chip camera. So to get short DOF it's not just a matter of throwing another lens in front of the camera. You can, but you're not going to get the same FOV.

The main advantage of a relay are

1) You're able to configure the optic so that it optimizes performances with your adapter.
2) A shorter profile. Cameras with interchangable lenses are BIG, and slapping an adapter on there makes it very unwieldly and poorly balanced.
 
^

yeah that's what I was wondering. Why do i need a relay to use my 35mm adapter on a 2/3 carmera. So it's about size and optimization.
 
Huy is right. A relay is small, the Letus short B4 relay is 68mm vs. 204mm for an HD ENG zoom lens, it should be faster, sharper, lighter and optimized optically for that company's DOF adapter/s. There is no guarantee how well it would work with another company's DOF adapter, but concievably, it should still be better than on the end of a big zoom lens.

Regarding a 1/2" relay lens, I know that Letus is going to offer a separate relay model vs. using a 2/3" to 1/2" adapter. Doing the latter would affect the field of view, ie; a 1/2" camera using a 2/3" to 1/2" adapter would mean the image would be magnified 1.5X.
 
.....this discussion is off topic... And I've just explained why twice but deleted it because I'm not use to this laptop (also just finished a long shoot and have been up 20 hours).

What Huy is talking about is the Focal Length Multiplier and everything he wrote is very much unrelated to what a relay lens is in relation to a DoF adapter. Or even what a relay lens is in general. It takes longer to explain why than it did for him to write it and since I explain it twice already but lost it I'm not doing it again. 16mm is still VERY MUCH INDISPUTABLY different in DoF than 35mm. And it confuses me that Dino agrees with Huy.

I don't think you understand what a relay is for especially in application and what I'm talking about. A particular camera system (i.e. 1/3", 1/2", 2/3", 16mm/APS, 35mm, whatever) should be optimized for the lenses it uses. The FoV of the lens should be intended for that sensor size. In still DSLR APS cameras you can use 35mm lenses but even then the sharpness, CA, and just about everything else that can be changes. The optics are not optimized.

I'm sorry if I'm being blunt. It's just because I bothered to explain for astigmatic only to be taken off topic and in a misleading and incorrect direction.
 
Marshallarts said:
What Huy is talking about is the Focal Length Multiplier and everything he wrote is very much unrelated to what a relay lens is in relation to a DoF adapter. Or even what a relay lens is in general.
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As far as I understand it a relay system simply replaces the lens on the camera to simplify operation (no more bumping focus, no light loss from having to zoom in to the GG). And it also allows you to design optics that take advantage of a particular adapter. This is important since the lens on such cameras as the HVX and the EX1 have been documented to have edge to edge sharpness issues when used with adapters, so having a custom made relay simply takes the lens out of the equation.

Marshallarts said:
16mm is still VERY MUCH INDISPUTABLY different in DoF than 35mm. And it confuses me that Dino agrees with Huy.
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I don't understand your point here either. Depth of field is completely independent of sensor size. A 28mm lens (focal length, not FOV) made for a 16mm system will have the SAME DoF as a 28mm lens made for 35mm film at the same f-stop. The only difference is that that the 16mm version will have a smaller circle of illumination.

If I'm wrong at any point please correct me.
 
OK I'm jumping in...

Optics physics have some limitations... the best design (or the better performing) is the one that its for a limited uses in a very specific target and not able to do everything...

As you try to make an all around lens, that many problems you have to solve...

What Dennis is trying to achieve is very unique... as an engineering point of view is risky... in a marketing aspect, if he succeed and deliver a product that can outperform a prime lens system at the same aperture it will be an outstanding achievement... but then if not, then it will be a compromise that the user will take...

Until then he already had a difficult developing period due to very understandable reasons, for me I wish he will succeed... since I will have another option in my rental house... I don't want to sound pessimistic, I know Dennis is a perfectionist, but the optics have there own rules...

So the specific is much easier than the all around... in optics difficult equals to less performing... thats the bland truth...

As for if the dual mount is possible... that is an extra problem above all the others... Certainly for the design route that Cinevate and Letus has, I thing it will be a different relay (I don't wont to speak for them but, is what I undestand from their statements), there are B4 2/3 to B4 1/2 adapters in the market... I don't know how they will perform in such a combination...

On the other hand my approach is more modular and probably I can do it... I can't say anything more, I will just check the possibility...

Disclaimer: I have to remind, that I start building a relay because I couldn't wait any longer.... If I have an outstanding alternative like Cinevate or Letus I will use it in my rental business... and still sell my solution for the price that reflects its performance in the market...
 
Evangelos Achillopoulos said:
What Dennis is trying to achieve is very unique... as an engineering point of view is risky... in a marketing aspect, if he succeed and deliver a product that can outperform a prime lens system at the same aperture it will be an outstanding achievement... but then if not, then it will be a compromise that the user will take...
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Evangelos,

A relay that zooms isn't a priority for me, I would just want a B4 relay lens that is set for Academy. According to what I've read, theoretically, if you had a zoom lens with 11 elements, 4-5 elements would be used for ensuring focus at different distances, the remaining elements would be used to address sharpness, MTF, contrast.

A prime relay lens that had a similar number of elements could use those elements primarily for ensuring good light transmission, sharpness, MTF, contrast. In fact, a longer prime relay with more elements could yield less light loss, and have better sharpness, MTF and contrast.

Does this make sense to you?

Regarding DOF, if a 35mm and 16mm lens have the same focal length and assuming the same aperture, wouldn't the DOF be the same? It's just that the
magnification would be greater for the 16mm due to the smaller film plane?

If I am close to accurate, wouldn't using a relay lens designed for 2/3" and putting a 1/2" adapter on it cause the image to be magnified 1 1/2 times? The
DOF would be the same, but not the FOV?
 
It would be great to have both 1/2 and 2/3" chips serviceable in one package, but that would have resulted in too many image compromises. Our engineering challenge was indeed a stretch in order to achieve several things:

1. Engineer a lens with the ability to resolve well beyond a 2/3" chip at native 1920x1080 res and do it with edge fall-off, sharpness, (MTF properties) that rival/exceed our Zeiss prime lens collection characteristics. This basically means a very punchy organic look with extremely low CA and SA characteristics.

2. Relay both SLR and Cine frame gates while maintaining the above. Optics technology has come a long, long way making mulit-format completely possible with minimal compromise.

3. Achieve an f/stop rating that would rival the typical stock B4 lenses....but be sharper wide open, and of course be packaged as compact as possible.

4. Have lockable rings to handle zoom, back focus and aperture.

To do this all has required nearly 18 months in CAD based design, sourcing exotic glass, and using coatings that make this lens completely world class. It's also by far the most expensive R&D undertaking that I could imagine for a small company like ours. The primarly target for this project is 2/3" chips but rest assured that we will not let our investment in this project rest with that chip size :-) Target retail is still at $2400.
 
Thanks for the info Dennis, great to learn from the source. I know that Letus has spent a lot of money in development as well. A big commitment indeed for Cinevate and Letus. Now we have a better idea of why the Pro35 was so pricey.
 
Dino said:
Regarding DOF, if a 35mm and 16mm lens have the same focal length and assuming the same aperture, wouldn't the DOF be the same? It's just that the
magnification would be greater for the 16mm due to the smaller film plane?

If I am close to accurate, wouldn't using a relay lens designed for 2/3" and putting a 1/2" adapter on it cause the image to be magnified 1 1/2 times? The
DOF would be the same, but not the FOV?
Click to expand...

I'm getting a little annoyed by this 16mm has the same Dof as 35mm claim. Let's look at the facts. I do realize Huy's first claim is partially correct in that he states, "To clarify, a 16mm lens yields the same DOF and FOV as it's 35mm focal length equivalent". I guess it would also have the same FoV but it was never intended to have the same FoV since it's in use on a different camera system and the flange distances are different so why suggest it. There's no reason to be talking about focal length equivalents in the first place. The whole topic is 16mm vs 35mm not 16mm versus its 35mm focal length equivalent. Still then the topic changes to effects that take place because of the focal length multiplier in which the DoF stays the same "due to the smaller film plane" as you state. But 16mm and 35mm when used properly on the correct systems still have different depths of field and it's ridiculous to suggest otherwise since this whole thread is about DoF adapters whose entire existence and marketing depends on the fact that they are different. That's why they're being manufactured. That's what a 35mm Depth of Field adapter is! Would you really spend thou$ands of dollars on a DoF adapter if you thought it does nothing to the Dof???

When you suggest all that changes between two lenses, one 16mm and one 35mm, with the same focal length and same f/stop is the magnification because of the sensor size, then you are also admitting the 16mm has a magnification factor which means it is much more telephoto that the 35mm lens would look on a 35mm system.... But this is the focal length multiplier. In this case we're just slapping lenses designed for another system on a different one and the FoV doesn't change, just the crop factor.

There are reasons why we aren't putting 16mm lenses on 35mm cameras and visa versa. And it isn't simply because the mounts are different. The focal flange distance is different, the systems are optimized for the FoV for that sensor size. Optimized for exactly those characteristics you describe earlier. If you look at test charts (on dpreview.com for example) and see what happens to quality with even the best new lenses as they try them on 35mm and APS DSLRs, you see the characteristics completely change. And there's a much bigger difference between 35mm lenses and 16mm. (I mention 35mm and not APS because some DoF adapters have a 35mm GG and are intended for still 35mm lenses). But then why if we're being so sensitive in knowing these optics are specific to a particular system and it's best to leave it optimized for those systems, why are we considering 35mm and 16mm being interchangeable between systems and having the same depth of field other than in theory (and to irritate me :)).

Dino is correct about putting a 1/2" Dof adapter on a 2/3" relay (not sure about the math since my brain is fried now) but still that's because of the magnification factor on the GG.


Dennis and Evangelos,

I'm very sorry to go on that rant taking my own topic further off topic. Maybe you can correct me if I'm wrong here. I may be (i'm not the certified optics expert). What you state regarding my original question is what I expected. The more you need it to work on multiple systems the more compromises you need to make. Specifically I've always wanted to know more about how relay lenses operate optically. Still it's exciting to learn about your multi-format relay. And learning of this 2/3" to 1/2" converter for a relay is interesting though I suspect it would cause optical changes that would fall off from your Zeiss target specifications. Thanks you very much for your feedback, it really means a lot to learn from your experience.

Evangelos -- if it ends up working for you let us know! "On the other hand my approach is more modular and probably I can do it... I can't say anything more, I will just check the possibility..."
 
I think some things got lost in the translation in this thread. Everybody is correct, so I'm not sure what the issues are exactly?

If there must be a choice, my vote is for a 2/3" relay lens only because I work more often with 2/3" HD cameras. The only 1/2" camera I rent is the EX1/EX3 and the lens on that is short enough to make the rig workable. An HPX2000 / 3000 with a long zoom and an adapter rig is ridiculous which is why the Pro35 still rules the 2/3" adapter world.

The investment that Dennis and Letus are making sound substantial and I hope it gives them in-roads in the higher end HD rental markets where Pro35 still dominates. Unfortunately the cost of a Letus Ultimate plus relay lens would surely make me and most other DP's consider such equipment production rentals rather than personal accessories to own. That's the way it should be for most DP's. Be an artist, not a gear owner/renter.

P.S. and Im a little ashamed to know these nerdy technicalities - in terms of Depth of Field and Focal Length and sensor/gate size: It is not EXACTLY true that a certain focal length lens has the same DOF on 16mm or a 2/3" HD camera say and a 35mm Academy gate. The format the lens is being used on, besides differences in lens coverage, will change the perceptual definition of what's in focus and what's out of focus. Please just try this yourself if you get the chance. Put a Zeiss 50mm digiprime on a F900R and put a Zeiss 50mm superspeed on a 35mm camera with Academy gate. Even to the eye you will notice that perceptually the 35mm Academy view will have a greater DOF than the 50mm on the F900R. It's something known to focus pullers who have worked in both formats. You can get away with a little more on the bigger cameras for the same lens. Not by much, but it helps!
 
Marshallarts,

I agree that putting a 16mm lens on a 35mm DOF adapter will yield very different results than using a 35mm Cine or SLR lens--please don't drop kick me! The 16mm lens won't be too much different than a 2/3" camera DOF and FOV. Here are some images I shot a few years ago illustrating the differences between 1/3" CCD, 2/3" CCD and 35mm Academy w/DOF adptr:
 

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great, i'm in the market for one of those, can't wait to put 35mm adapter on my hpx500, this is all i ever needed! and i hope it will work with other adapters like sgblade :D
 
wait a minute....:huh: I never mentioned putting anything on the end of a DoF adapter (btw, nice pics Dino). But is that where the confusion started?:
astigmatic said:
here's another question. Why not just use a 16mm zoom lens(or the fixed scarlet;s zoom) instead of a relay? I'm not quite grasping the advantages of a relay...
Click to expand...
I only *briefly* described to astigmatic (post #3) why you'd use a relay instead of a 16mm lens to begin with. Meaning why I would use a relay lens to therefore use a 35mm DoF adapter (on a camera body that doesn't already have a fixed lens so you would therefore need a relay lens in order to use a DoF adapter--BTW, this is the ONLY reason I would use one) instead of simply using a 16mm or digiprime.

Still..... I am very confused by this statement:
dadoboy said:
Even to the eye you will notice that perceptually the 35mm Academy view will have a greater DOF than the 50mm on the F900R.
Click to expand...
Am I loosing my mind? I thought it was very common knowledge that 35mm has a shallower DoF than 16mm. That to achieve as shallow a Dof in 16 you have to open up a few stops. Literally EVERY DoF chart in existance will tell us this. How on earth can we not be agreeing on this. And I'm not saying a little, it's a very substantial amount, to the point where it's an important decision in choosing camera systems. Really, isn't this elementary?

Dino, seriously, great pics! Doesn't that very much illustrate the point here? 16mm doesn't get us 35mm DoF. If it's dark out and you can't open up anymore, and don't want to compromise lens MTF & CA by opening up, that is a disadvantage to 16mm. That's why 35mm is better if you're want to achieve a smaller DoF (aka, a 35mm "look"). That's why we use "35mm DoF adapters"!!!

35mm and 16mm have very different DoF! The bigger the sensor size the shallower the DoF! This is 1st grade here!

I'll post some links later, just flew to Austin for a shoot. I'm just sorta wondering if I'm loosing my mind.
 
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