PDA

View Full Version : 35mm lens adapters?



Paper_bag
07-05-2012, 05:07 PM
Hi! I'm very ignorant about this; hopefully someone who knows could write something on the topic. But why isn't anyone talking about using 35mm lens adapters to get around the issue of sensor size? Is there a good reason these won't work? Can current adapters be adapted to the BMC? Or would Letus, Redrock et al have to bring out something new?

Tom
07-05-2012, 05:28 PM
I guess its because many people feel its not worth the light loss, flipped image, degraded image, extra bulk etc for having only slightly more dof per fov or for having a wider capability due to the large focal plane.

I used to use a dof adapter on a crappy 1/3 inch sensor camera because i wanted shallow dof and to use nice lenses. The difference it made to that camera was good enough to justify using it. The difference it will make to a bmcc is probably not worth it for most people, i know i dont feel its worth it.

Although smaller than 4/3rds, its still a relativly large sensor! You will be able to get shallow dof with this camera without having to go very telephoto. In terms of wide shots, 18mm equiv is easy to obtain with a 500 lens, and 18mm is fairly wide. Ive found that for my work i rarely need to go wider than 24mm, 20 at a stretch, so 18mm is plenty wide for me.

Obviously i can only speak for myself and im not dismissing dof adapters out right, just that i dont think the trade offs are worth it for this camera. :-)

nickjbedford
07-05-2012, 05:52 PM
Personally, I don't find the sensor crop much of an issue. It's been shown in John Brawley's early videos that a very nice shallow depth of field (just about the right amount) is very achievable with the right glass (primes).

Brian@202020
07-05-2012, 06:13 PM
Hi! I'm very ignorant about this; hopefully someone who knows could write something on the topic. But why isn't anyone talking about using 35mm lens adapters to get around the issue of sensor size? Is there a good reason these won't work? Can current adapters be adapted to the BMC? Or would Letus, Redrock et al have to bring out something new?

The sensor crop to me doesn't warrant the light loss and extra weight just to get a little shallower DoF. The crop really isn't that bad.

ryaninoz
07-05-2012, 08:15 PM
I think the size of sensor the bmc has is perfect for shooting motion. You can still achieve shallow DOF but you aren't constrained by it. I would have been happy with a 16 mm sensor. For me it's latitude, colour depth and the fact that after twenty years of shooting with large heavy cameras I feel like the small form factor combined with high quality will set me free as an operator.

Grug
07-05-2012, 08:55 PM
Well I love larger imaging formats, the bigger the better. 35mm adapters will allow you to use any lens mount you like, which is another benefit. The biggest issue is the need for a relay lens to sit between the camera and the adapter, without that, you couldn't use one anyway.

Andrew
07-05-2012, 11:10 PM
Hi! I'm very ignorant about this; hopefully someone who knows could write something on the topic. But why isn't anyone talking about using 35mm lens adapters to get around the issue of sensor size? Is there a good reason these won't work? Can current adapters be adapted to the BMC? Or would Letus, Redrock et al have to bring out something new?

It was discussed a bit here.

http://bmcuser.com/showthread.php?179-The-Right-DOF-Adapter-for-you-and-your-BMC-camera-if-needed&highlight=35mm+adapter

Paper_bag
07-11-2012, 12:39 AM
Personally, I don't find the sensor crop much of an issue. It's been shown in John Brawley's early videos that a very nice shallow depth of field (just about the right amount) is very achievable with the right glass (primes).

Quick thought on this -- is it fair to say that 35mm adapters with a BMC aren't just about shallow depth of field? Wouldn't they also give you access to a bigger field of view than you'd otherwise easily get? Particularly useful for cramped environments?

Grug
07-11-2012, 12:54 AM
Quick thought on this -- is it fair to say that 35mm adapters with a BMC aren't just about shallow depth of field? Wouldn't they also give you access to a bigger field of view than you'd otherwise easily get? Particularly useful for cramped environments?

Perhaps, but since you can readily access 10mm rectilinear lenses that will offer a FoV equivalent to 23mm on full-frame - I don't think that's such a big issue.

23mm-equivalent is seriously wide.

21mm-equivalent (i.e. 14mm lenses on S35mm) is about as wide as anyone goes in conventional production, and even then, it's mostly just for shots that use the ultra-wide perspective to create a certain sense of distorted reality.

Paper_bag
07-31-2012, 04:20 AM
I'm still pretty intrigued by this whole idea of using 35mm adapters with the BMC. Yes, it's a pain in the butt, for all sorts of reasons, and would degrade the image quality, but maybe under some conditions it'd be worth it.

But here's two quick thoughts:

1. Joe Marine over at Nofilmschool reckons you'd need to mount a 300mm lens on the BMC to properly use one of the adapters designed for a 1/3" sensor. I've no idea how to do the calculations to arrive at this focal length, but there you go. Perhaps the Canon 100-400 would be the go-to lens in this case. And, given the size of a 300mm lens, the whole rig mightn't fit on a normal set of rails -- you'd have to put two tripods close together, or something equally unwieldy and dodgy.

2. Another way to get shallow depth of field, apart from ND filters, long lenses and blocking, is fixing it in post, though of course it's never going to look as good as in-camera. One of Andrew Kramer's first tutorials was about this. From memory, it involved two layers, a feathered mask around the area you want to keep in focus, and a lens blur effect on everything else.

Grug
07-31-2012, 07:36 AM
I'm still pretty intrigued by this whole idea of using 35mm adapters with the BMC. Yes, it's a pain in the butt, for all sorts of reasons, and would degrade the image quality, but maybe under some conditions it'd be worth it.

But here's two quick thoughts:

1. Joe Marine over at Nofilmschool reckons you'd need to mount a 300mm lens on the BMC to properly use one of the adapters designed for a 1/3" sensor. I've no idea how to do the calculations to arrive at this focal length, but there you go. Perhaps the Canon 100-400 would be the go-to lens in this case. And, given the size of a 300mm lens, the whole rig mightn't fit on a normal set of rails -- you'd have to put two tripods close together, or something equally unwieldy and dodgy.

2. Another way to get shallow depth of field, apart from ND filters, long lenses and blocking, is fixing it in post, though of course it's never going to look as good as in-camera. One of Andrew Kramer's first tutorials was about this. From memory, it involved two layers, a feathered mask around the area you want to keep in focus, and a lens blur effect on everything else.

I don't think you'd need 300mm, from talking to the guys at Letus, trawling the interwebs, and doing some maths - it looks like you'd need about a 100mm lens (and possibly a close-focus diopter) to focus on the ground glass.

Canon make quite a nice 100mm f/2 which is pretty reasonably priced - so that might be an option.

I have to say though, after seeing what JB was able to get with T/2 lenses in the Casey footage, I'm just not as worried about this as I was before. Perspective is still nicer with a larger sensor, but it looks like subject isolation won't be a problem.