FAQ like Info about 35mm lenses

The F1.2 is just a half stop faster. ( hardly noticaebale unless they are Directly compared split screen) But the Canon FD 55mm s.s.c. F1.2 is a much sharper lens than the 50mm s.s.c. F1.4.
 
im having a really hard time understanding what type of lens i need to get to attach to a letus35a adapter. i am going to buy a 72mm threaded letus35a so i can attach it right on to my dvx, and then it is my understanding that i will need to get another lens. so, in other words: DVX --> ADAPTER --> LENS is this right? i'm really confused.
 
yea but you need an assortment of high quality lenses to get all the different fields of view. Telephoto lenses for long shots, wide angel elnses for closeups in small spaces. etc. Its not cheap and it complicates your shoots. think hard before making the leap.
 
thekyleman71 said:
im having a really hard time understanding what type of lens i need to get to attach to a letus35a adapter. i am going to buy a 72mm threaded letus35a so i can attach it right on to my dvx, and then it is my understanding that i will need to get another lens. so, in other words: DVX --> ADAPTER --> LENS is this right? i'm really confused.
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Take a look at wikipedia's explanation.
http://en.wikipedia.org/wiki/Depth_of_field_adapter

I'm seriously not trying to push the Snod35 DVD on you, but the "depth of field explained" and "35mm adapters explained" chapters will clear your confusion. :)

I think that before you get the adapter, you should spend some time learning about depth of field and 35mm lenses. I don't mean this in a bad way at all. To get the most out of an adapter, you will need to have a pretty good understanding of both. If you google around, there are tons of sights with good info.

To answer you question..

DVX > 35mm adapter > 35mm lens

The adapter will screw right onto the front of your DVX (with 72mm threads). The adapter will not come with a 35mm lens, so you will have to buy one (to start with). These are the lenses that are made for 35mm cameras. Different brand lenses have different types of mounts. A lens mount is simply a circular piece that the 35mm lens is screwed or locked into. When you buy your adapter you will need to choose a style of lens mount. So for example, if you want to use Nikon 35mm lenses, you will most likely want to get the adapter with an F mount... which most all Nikon lenses use. Canon has several different types of mounts, so this might require some more research.

Don't rush yourself into buying a 35mm adapter... there is plenty of other equipment that should come first (in my opinion).... dolly, jib, field monitor, lights, etc.
 
hatsoff2halford, you might want to ask Ed specifically... but from my experiences it will mostly depend on what Ground Glass you are using. The lens you linked to is a wide angle lens. The thing to keep in mind with wide lenses is that the aperture is much smaller for a given f/stop when compared to a 50mm focal length (aka "normal" lens) or telephoto lens.

Aperture size = focal length / f-stop number

If you input the numbers into this equation, you will find that f/2 on a 50mm lens creates an aperture that is 25mm in diameter while f/2 on a 28mm lens creates a aperture that is only 16mm in diameter.

This smaller aperture can create a pretty nasty hot spot in your images... even with a plano-convex. If you get the hot spot or not (or how bad) will depend on how well your GG diffuses the light.

The lens itself is a Vivitar. Myself, I would only buy Canon or Nikon. I bought a canon 2.8 28mm from ebay not too long ago for around $40. A faster lens than 2.8 would be better, but the price will make a pretty big jump.

EDIT: I agree with Timur... ebay is risky. So far, I am 4 for 4 when it come to getting good lenses from ebay sellers. Make sure they have 99.9% positive feedback. Ebay is always a gamble I suppose.
 
I'm using a Nikon D focusing screen as my GG. I'll probably just get a Canon fd lense, even if it is slower.

Thanks a ton for the replies.

-Logan
 
I'm using a Canon FD f/2.8 28mm and an FD f/1.4 50mm. f/2.8 is a little slow for the 28mm, but can still produce nice images.

Keep in mind that "fast" and "slow" just refers to the lowest f/stop setting. So a lens with a minimum f/stop setting of f/2.8 is considered "slower" than a lens with a minimum f/stop setting of f/2. It doesn't mean much more that that.

If you do end up going with Canon FD, there is a little "trick" you will need to do with some FD lenses to engage the f/stop lock lever.

f_stop.jpg


The lever above is normally engaged when attached to a camera. I just cut a small piece from some from brass flat stock (hobby stores), cut it to length, slid the lever over, and inserted the brass piece. Easy fix and works fine. I had forgotten it was even there until you mentioned FD lenses.

Good luck
 
snodart said:
I'm using a Canon FD f/2.8 28mm and an FD f/1.4 50mm. f/2.8 is a little slow for the 28mm, but can still produce nice images.

Keep in mind that "fast" and "slow" just refers to the lowest f/stop setting. So a lens with a minimum f/stop setting of f/2.8 is considered "slower" than a lens with a minimum f/stop setting of f/2. It doesn't mean much more that that.

If you do end up going with Canon FD, there is a little "trick" you will need to do with some FD lenses to engage the f/stop lock lever.

f_stop.jpg


The lever above is normally engaged when attached to a camera. I just cut a small piece from some from brass flat stock (hobby stores), cut it to length, slid the lever over, and inserted the brass piece. Easy fix and works fine. I had forgotten it was even there until you mentioned FD lenses.

Good luck
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I'm a little confused here. Why does one have to lock the f-stop? My lens (50mm f1.4) stays open all the way when I place it onto the letus. I'm assuming one wants it wide open so as not to lose more light.
Jgastelb
 
The aperture will not function unless that lever is slide over and held in place. The goal with using the small piece to keep the lever in the engaged position is so that the aperture will function normally. This way, when you adjust the f/stop, the aperture will react accordingly.

You want to be able to adjust the f/stop of the lens as it is an important tool in setting up your images. It will allow you to alter the DOF and fine tune your exposure. Also, with most lenses... wide open is not the "sweet spot" so the images may not be as sharp as is possible with a given lens.
 
snodart said:
The aperture will not function unless that lever is slide over and held in place. The goal with using the small piece to keep the lever in the engaged position is so that the aperture will function normally. This way, when you adjust the f/stop, the aperture will react accordingly.

You want to be able to adjust the f/stop of the lens as it is an important tool in setting up your images. It will allow you to alter the DOF and fine tune your exposure. Also, with most lenses... wide open is not the "sweet spot" so the images may not be as sharp as is possible with a given lens.
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Would it be ok to deal with the aperture in cam. Does it not also affect the sweet spot this way? I'm not trying to argue -- just curious. If I stop more on the lens then that means I lose more light. i.e. if the sweet spot for in cam is f5.6 or so and f2.8 or more in lens then 'Oh, My God' I will need more lights than a scene in CSI Vegas.
Jgastelb
 
I put a piece of a paper clip sustained by some gaffer tape and it seems to hold. I'll have to test it out during the day when I have plenty of light. Should I try to offset exposure in cam as well then besides the nd filters?
Jgastelb
 
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Hey J.G. It's Matt from the DVXUser.com meeting in Denver a couple weeks back.

Here's what I understand:

Try to keep BOTH lenses at their own sweet spot - that is, a stop or two closed down from full open. For the DVX, this is about F4.0, and for your SLR lens, that varies. I have an F1.2 50mm, and I try to keep it at F2 to F2.8.

Hope that helps. Take it easy.
 
wjm said:
Hey J.G. It's Matt from the DVXUser.com meeting in Denver a couple weeks back.

Here's what I understand:

Try to keep BOTH lenses at their own sweet spot - that is, a stop or two closed down from full open. For the DVX, this is about F4.0, and for your SLR lens, that varies. I have an F1.2 50mm, and I try to keep it at F2 to F2.8.

Hope that helps. Take it easy.
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Hey Matt,
Thanks for the reply. I'll try that. I really am eager to see a difference on that shallow depth. Because right now I'm probably not getting more than an inch of in focus with what I have been doing. It's either the nose or the ears that will stay sharp. From what I have seen your adapter doesn't seem to lose much light. Your natural light tea clip was not as underexposed as some of my stuff. And, raising the luminance in post brings way too much grain. I guess I just need more lighting to fix this issue.

BTW, Ken is having a lighting lecture at KBDI this Saturday. Email back if you're interested.
Jgastelb
 
jgastelb, wjm is correct. Ideally, you want to keep both the DVX (or whatever camera you are using) and the SLR lens close to the "sweet spot" (I'm pretty sure that Barry Green had said it is f/5 for the DVX). On my Canon 1.4 50mm, the sweet spot is f/5.6. This does not prevent me from using other f/stop settings on the SLR lens, but it is good to keep in mind. There are times when I want the take advantage of all the sharpness available and then other times where altering the DOF is more critical.

I do try to keep the DVX close to f/5 as much as possible. So for example, if I want a very shallow DOF, I might set my SRL lens to f/2 or 2.8. If I am using 1250 total Watts of lights, the chances are that I will need to use an ND filter so that I can get the DVX to around f/5. Without the ND filter, The DVX might have to be set to something more like f/11 (not the sweet spot). One the other hand, if I want a longer DOF or if I am using a wide lens, then the chances are that I will need more light. So let’s say that there is going to be a good deal of movement by the actor, I might set my 50mm SLR lens to F/8 (for a slightly longer DOF). So to do this I might either have to settle for an f/stop on the DVX that is < f/5 or add more light to the scene.

Lighting is a huge factor... not just for adapters, but for DV in general and for the overall cinematic value. If you are looking at a scene (with your eyes and not through the camera), and it looks way too bright... then the chances are that it will look just about right through the camera. Keep in mind that this situation is not just specific to adapters. It also holds true with straight DV images. Good lighting is a challenge with and without 35mm adapters. 35mm adapters really don't change things all that much as far as lighting goes. You just need a little extra light or you just have to settle for a little less than f/5 on the DVX at times. Of course this all depends on just how much light is lost with the SLR lens and adapter that you are using.
 
So what adapter are you using? I keep hearing people say that you need at least 2k (indoors) of total light for most adapters. I have the letus and it loses so much light. I do have about 2k at home but some of it is work lights. One of them is
a softbox (500watts). I know, I know... work lights are not ideal and I'm working on getting a 1k with barndoors. I'm not worried about close ups since I can simply light close enough to the subject and the inverse law works real sweet. I'm mostly concerned about those medium shots. The wide shots are usually brief anyways.
Jgastelb
 
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I'm using a DIY vibrating adapter (Snod35). I have yet to officially test the light loss (there is some of course). Both Cache and The Seeing were shot with it. The average total amount of light used for Cache (excluding exterior/day shots) was around 750 - 1000W. For The Seeing, the average was more like 1250 - 1500W (it had more wide shots).

I have yet to try out the Letus, so I don't know if there would be that much of a difference in light loss between the Snod35 and the Letus.
 
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