Shallow focus adapter for HD100?. Brevis, M2 or Letus HD?

[Jose L. Martinez]

I'm trying to find the best option for my HD100, and these three models seems quite close to each other, but still cannot decide, so I hope any of you can help me with your experiences.

First the Letus seems the best bang for the buck, with the main advantage of being a relay system, so I can pass the stock lens (with all the color problems and other flaws) and have a 'as clean as possible' image, by using less glass. Also, it provides an already flipped image, so I don't have to flip it in post. The biggest drawback for me seems the 1.9x magnification it produce. I don't understand quite well why it does so. It is my understanding that this magnification will reduce the FOV (a 50mm lens will produce a =/ 75mm field of view, but with a 50mm depth of field), thus negating part of its 'raison d'etre', ie: the other adapters without this magnification can produce a far shallower depth of field with the same focal lens. If so, is there any way to overcome this problem?, perhaps using some multiplier (or...divider? ;-)) that can return the lost FOV?. I got to see some tests (xH1) and altohugh are quite nice, it seems it provide the less shallow DOF of the three on the same conditions.

Second, the Brevis 35a seems another nice choice, particularly with the new diffuser. It seems the brighter of the three, but it is not a relay apapter (and the stock hd100 lens is bulky enough, and the more glass you put, the less definition you get). It is still portable enough and seems to produce quite nice images. I've read some comparisions where the GG grain is visible at higher shutter speeds (It is my understanding that with higher shutter speeds->less light->less D.O.F-> you can use directly the stock lens, so...). My biggest concern is that you still have to use the stock lens, the upside down image, and having visible gg sometimes, since some of my projects will have a filmout.

Third, the Redrock, which seems the sturdier of the three and looks the more 'professional', but it isn't a relay lens, loss more light than the brevis and the letus. Also producing a upside down image, but no magnification. It seems quite close to the brevis in terms of features, but feel more (I haven't tried any of them, so I can only judge by other people impressions, in this board and others). In price, both brevis and M2 seems quite close.

So, since my camera is a HD100, my lenses would be mainly Nikkors (still ebaying for zeiss-es), and my bigger concern is quality and realistical DOF, way ahead of price or bulkyness, what do you think would be the best bet for dramatical, one camera production (features, shorts, promos, music videos, etc).

Also, I've been unable to find any info on how noisy these units are?. Anybody can help?

Cheers,

Jose

[Chris Hurd]

Moved from JVC ProHD to Alternative Imaging Methods.

[Ben Winter]

Originally Posted by Jose L. Martinez

(It is my understanding that with higher shutter speeds->less light->less D.O.F-> you can use directly the stock lens, so...). My biggest concern is that you still have to use the stock lens, the upside down image, and having visible gg sometimes, since some of my projects will have a filmout.

Not so at all! Shutter speed has absolutely nothing to do with depth of field. I can crank up my shutter to 1/5000 until my image is barely visible at all, but the DOF will be the same as it was at 1/60. I think you might be getting this light/DOF relation from the aperture. Closing down the aperture gives you deeper depth of field (what you call "less" but because of the definition of depth of field this actually means "more" dof) and a darker image, but this is only a characteristic of the aperture and not a relationship shared by any other means of darkening the image.

Since your projects will be going to filmout, I would recommend looking into the Brevis or M2. There are a couple reasons: there isn't actually "less glass" in the Letus, just more glass arranged in a space-saving design. The image goes through the SLR lens, hits the ground glass, bounces off of four mirrors, and goes through another SLR lens. Collectively that's something like 11 separate pieces of glass. Also there is no way to optically return the lost FOV once it's been lost in the Letus system.

If the Brevis requires one of those big fat 72mm achromats to work on the HD100 (not sure if it does off the top of my head) then you're looking at a pretty heavy front-end...however it's been done and you'll find a lot of HD100 owners who use the M2 as well, It's a bulky setup, but if you don't plan on doing run and gun, which seems to be the case, the Brevis or M2 should suit you fine. Also it seems like your priority is good quality DOF.

I don't know about the noise on the M2 or Letus but from my past experience the Letus35a has been extremely quiet if not silent and from current experience, the Brevis produces a small hum that disappears past a 4-5 inch proximity. Neither are of any concern really.

I would also suggest looking into the SG35pro as I've seen some really stunning footage from that thing.

[Chad Terpstra]

Jose,

I'm in the same boat as you since I have an HD100 and am looking for an adapter. I was really considering the Letus, but then started to question the magnification issue and found it wasn't something I wanted to work with after all. If it didn't have this problem it would probably win my vote as the images it can produce are very crisp and it’s a quick inexpensive solution.

Now I'm actually getting ready to buy the Brevis for a few reasons:

1. It's bright (or can be with the stock difuser)
2. It's easy to setup
3. There's a great community at Cinevate.com (growing the way the M2 forums did)
4. Dennis is planning on making a flip module due out in a few months after he makes a few other essential pieces of gear (matte box & FF). It will turn the image upright at the cost of some more light loss. Also following all this he did mention a plan to make a relay lens for the HD100 and Canon XL cameras. Nothing for sure, but it’s good to know the product I buy now is supported for future enhancements.

I also like the switchable GG/diffuser for different levels of light loss versus quality.

I don’t have it yet so I can’t put myself 100% behind it (or it anywhere above any other adapters), but I thought I’d share my recent thoughts. If I manage to get it within the next few weeks I will most certainly be posting footage. ;-)

[Sam Jankis]

Buy a relay lens for your HD100 and get the Brevis. It'll be barely longer than the stock lens setup (unless you have a huge 35mm lens). If a relay lens can be used, that's the best way to go IMHO.

[Fabrice Hoffmann]

Lot of people on this boat... I'm looking for an HD200 or 250 and for an adapter too. If I understand Sam, you are talking about an a relay lens to put between the camara body and the adapter. Does anyone has an idea if it already exists, and has been tested somewhere ?

Thanks.

[Chris Barcellos]

I am not an HD100 owner, but I have built my own adapter based on the Redrock Do it Yourself plans and kit. I built it for my FX1.

There seems to be misunderstanding what these adapters do in this thread. They all do the same things, employing different methods. Simply speaking you are using a 35mm lens to send an image to a ground glass. THe adapters differ in that they all move the ground glass to avoid imperfections on the ground glass from marring the image. They either vibrate the ground glass or they spin a disk. The video camera, with whatever lens you have on it, then records that image right off the ground glass. It is upside down. We use magnets to flip the image in the LCD of our cameras, but that doesn't flip the actual image going the camera. Some simply turn their cameras over to get a right side image recorded to tape. Others simply flip the image in post.

Some manufacturers now have a mirror system to flip the image.

Because most cameras don't have ability to close focus, a lens between camera lense and ground glass is required to allow close focusing. People started out rigging with simple close up lenses, but face a lot of issues there with the imperfection. Achromats were developted for that purpose.

[Toenis Liivamaegi]

The cheapest relay lens for HD100 start from $2000 and are sold by P+S but those are designed for projecting 22mm image circle from adaptor to camera head or in this case the 3CCDs of HD100 camcorder.

I`ve done quite much research about possible c-mount (relay) lens that are designed for HD machine vision applications but I`m still not sure if and wich lens to use considering barrel distortion and chromatic abberations.

If I´m not mistaken Navitar makes custom relay lens even without iris.
What should we know before we can order a relay for hd100?

HD100 flange distance - 31mm?
Realy lens M.O.D. from GG - 50mm?
Object dimensions at M.O.D. - 36x24mm or smaller?
What should be the sufficent resolving power - at least 1.5Mpix maybe even 5Mpix?

In my eyes HD110/200 is the perfect adaptor cam if relay lens would be available.

See here for Fujinon c-mount CCTV lens specs
When c-mount lens are used on HD100 31?mm flange distance it`s MOD decreases significantly or maybe even too much.

Tim Dashwood has used 25mm c-mount lens as relay lens for DIY mini-35 maybe he can chime in and give few more directions here.

Originally Posted by Tim Dashwood

However, I had a C-mount adapter machined last year that sits flush with the bayonet mount.
Of course, since the back flange distances are completely different, it turns the C-mount lens into a macro lens with a very narrow FOV.
I did this for my home-built mini-35 setup, using a c-mount lens as the relay from my ground glass.

Best regards,
T

[Bob Hart]

A Cosmicar f1.8 25mm C-Mount lens is also what I have tested into 1/3" CCD security camera using a replica of 24mm x 18mm GG image frame.

The C-Mount lens was offset about 8-10mm forward of its normal flange to focal plane which confirms Tim Dashwood's experiment, more or less.

[Sam Jankis]

Doesn't the LetusFlip come with a relay lens?

[Andrew Todd]

Originally Posted by Sam Jankis

Doesn't the LetusFlip come with a relay lens?

yes ....

[Sam Jankis]

If I had an XL-H1 or HD100, I'd try to purchase a Letus relay lens... and get the Brevis.

Not that the Letus doesn't have it's strong points...

[Ben Winter]

Originally Posted by Sam Jankis

If I had an XL-H1 or HD100, I'd try to purchase a Letus relay lens... and get the Brevis.

Not that the Letus doesn't have it's strong points...

Not so sure the Letus is that reverse-engineerable...Dennis is coming out with a flip unit upgrade for Brevis units so I think it might be wise to just hold out....

[Sam Jankis]

I'm not referring to the flip module... just the relay lens.

BTW, this thread brings up something to be concerned with when using a relay lens:

Originally Posted by Taylor Wigton

As far as the M2 eating up alot of light: It's actually not really a factor of the adapter "eating up" light. It's more an issue that you really have to stop down your relay lens at least two stops to avoid lateral chromatic abberation. And it's great if you have a Nikon that opens up to f1.6, but the problem there is two fold. The lens portholes all the way open like that, as it is really designed to shoot at f4, and next, who can pull focus at that stop? A computer maybe. So your light loss with the M2 is a condition of the lenses that you are using which you really HAVE to stop down in order to get yourself in a realistic shooting environment.
...
I have tested relay lenses with the M2 and to date have not been all that please with the results.

[Toenis Liivamaegi]

Maybe lateral chromatic abberation occures because of relay lens are not designed for 3 CCDs?
It would make sense because lens' magnifications can vary very slightly with different colors. This means the image can be very slightly different sizes at different colors and when this happens, the colors don't line up perfectly and you'll see colored fringes towards the sides.

Regs,
T