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Old February 14th, 2009, 03:04 PM   #1
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Dof

Hello folks,
I just upgraded my equipment and bought a used REDROCK 35mm Adapter M2 micro series (with a Nikon connection)

Now I have a few questions:

1) I was really hoping to see DOF (depth of field) but looks like I'm only getting focus on the whole image only (cant control focus) Is it becuase of the kind of lens? I have a Vivitar 28-85mm lens... is this lens mabye used for landscape only? What should I be looking at when buying a lens for DOF?

Here is my test footage: DOF test on Vimeo

2) The image is filmed upside down. I do not mind rotating it in the editing process... but It would be easier to film with it right side up. Is there an easy fix?

3) The footage is a little darker than normal without the adapter... any ideas on what i can do?


Well thats all for now... I would really love to hear what kind of lens I should upgrade to...
Thanks in advance.
David
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Old February 14th, 2009, 09:25 PM   #2
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If that video has an example of your focus technique, that may be the problem.

You may already be doing this but just in case you're missing a step:

Before you begin, make sure that the camera is set to manual mode and that the GG is not spinning (i.e., turn off the adapter)

1) Set your camera's iris and the 35mm lens iris to wide open

2) zoom your camera's lens so that the GG completely fills the image

3) point your camera towards a bright light source and focus your camera's lens so that grain on the GG is sharply in focus. This is called setting the back-focus. Once that is set, do not touch your camera's focus or zoom going forward.

4) now close down the iris at least one stop on the camera's lens. You can adjust later if needed.

5) adjust the iris on the 35mm lens until the image brightness is correct.

6) do all of your focusing with only the 35mm lens. You'll get your shallow DOF. Remember that at the wide angle of your zoom lens, more of the image will be in focus.

The picture will also be darker than without the adapter. All adapters lose a certain amount of light.

Hope that helps.

P.S. some people prefer to set the back focus by setting the 35mm lens at infinity and then setting the camera's focus until the picture is clear. once set, leave the camera focus alone and use only the 35mm lens focus.

Hope that helps and sorry if it's just a rehash of what you're doing.
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Old February 15th, 2009, 01:52 AM   #3
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Sorry Marcel.


Your step one is a wrongie.

The iris of the SLR lens on front has to be closed as much as you can have it and still see an image if you are using the stationary groundglass method of setting relay focus. The object of closing the SLR lens iris is to provoke the groundglass texture into becoming most visible.

If you are using a resolution chart to set relay focus then you can do what you like with the SLR lens as long as you have the camcorder lens iris wide-open so that the lens presents its own shallowest depth-of-field to enable sharp focus on the groundglass. My personal preference for that is to set the SLR lens iris to its known sweetest spot for sharpest image onto the groundglass.

I also prefer when setting relay focus to a resolution chart, to have the groundglass motor actually running. That way, any microscopic runout of the groundglass is naturally compensated for. Additionally, the actual image within the depth of the groundglass texture is focussed upon, not the visible texture itself, a method which can get you just a few more lines of resolution but is worth the compulsive/obsessive effort.

In the vimeo clip a groundglass artifact should have been provoked with one against the light shot and does not seem to have shown. I think the new owner should enjoy what he has got once he becomes accustomed to it. The M2 was the smartest kid on the block for some time.

The M2 apparently presents a bit of an added problem for novices in that there are awkard internal repositionings of the groundglass which may have to be done to get things optimal. As a used item, this may have already been done by the previous owner or the previous owner may not have been successful, got vexed and on-sold the adaptor.

My personal preference is also to have the camcorder zoom set to the normal operating position and not mess with it after setting camcorder relay focus. Some camcorders when powered up go through a sort of lens zero-set process and sometimes relay focus can drift ever so slightly when the lens resets to the last used position. Meticulous attention need to be paid to relay focus if consistent results are to be had.

Last edited by Bob Hart; February 15th, 2009 at 02:05 AM. Reason: errors
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Old February 15th, 2009, 08:27 AM   #4
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oops. You're right, Bob. I did get it wrong, didn't I? That's what happens when you rush. Sorry for the confusion it may have caused.

It's just so automatic these days, I don't really think about the steps, I guess.
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Old February 15th, 2009, 09:27 AM   #5
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Speaking of automatic, not all autofocus were made equal. I have found that the Sony Z1 or FX1 autofocus is actually better at trimming relay focus than my own eyeballs. I don't leave autofocus on, I just give it about a five-second burst after focussing the SLR lens, then switch back to manual.

Very occasionally, if there is a really intense pinpoint bright light source, the autofocus may attempt to focus on infinity through the groundglass chasing the trace of aerial image which might just get through in this condition.

I don't think you will encounter that problem with the M2 as the groundglass diffusion is apparently denser than most others.
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Old February 15th, 2009, 12:22 PM   #6
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Well I asked a photographer friend of mine and he said that this Vivitar lens seems to be only for Landscape purposes... there is no focus on the lens (just to turn to zoom a tiny bit and i'm guesing the apature?) well this lens is a 3.5 - 4.5 but he's saying I need a 1.4 or around that.

Let me know if that makes sense and thanks for all your help so far...
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Old February 15th, 2009, 01:34 PM   #7
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Many zoom lenses have the zoom and focus on the same ring. You zoom to where you want and then turn the ring to focus. The zoom lens has a separate focus ring and is also a constant aperture lens, meaning the fstop remains the same throughout the length of the zoom. i.e, in my case from 37mm - 105 mm, it doesn't get darker.

What's the range on your Vivitar?

you're probably better off getting yourself some good prime lenses (non-zoom) to start out with.
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Old February 15th, 2009, 07:18 PM   #8
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Here is my exact lens: CANON FD fit Vivitar 28-85 f3.5-4.5 MC macro zoom MINT - eBay (item 300291346760 end time Mar-05-09 13:06:54 PST)

Seems like this lens is for macro/landscape purposes... am i right?

Let me know what kind of lens I need.

Thanks again.
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Old February 15th, 2009, 08:57 PM   #9
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28mm to 85mm is a pretty good range for a lot of things, not just landscape. Remember 50mm is considered normal view. 28 is wide and 85 is semi telephoto. The macro ability is just an extra function. My zoom has that. The only down side to this zoom is that the f3.5-f4.5. That means as you lose more light (image gets darker) as you zoom in.

It's an okay lens and will work with some practice, but again, you'd probably be better off getting a few prime lenses manufactured by Canon, in your case.
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Old February 20th, 2009, 10:06 PM   #10
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Here is an update:

I got a new lens 50mm 1.4 and seems like that solved the problem. It gave me the DOF that I was looking for. Check out the footage below:

DOF test on Vimeo

Any tips or comments would be appreciated.
Thanks
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Old February 20th, 2009, 10:37 PM   #11
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Quote:
Originally Posted by David Kovalev View Post
Here is an update:

I got a new lens 50mm 1.4 and seems like that solved the problem. It gave me the DOF that I was looking for. Check out the footage below:

DOF test on Vimeo

Any tips or comments would be appreciated.
Thanks
Looks good. It is easier with a prime lens than a zoom lens. You should still be able to get similar results from your zoom lens as well, it just take a bit more practice.

Also, the fact that you are indoors, using only available light, means that your lens' aperture was probably close to, if not wide open...meaning it was at f1.4. Having it wide open like that creates a shallower DOF than if it was stopped down to say, f4. When you shoot outside on a bright day, you will have to stop down more, creating a deeper DOF. Take a look at these screen grabs I posted in this thread: http://www.dvinfo.net/conf/alternati...1-footage.html.

Both shot outside and on the same lens you're using, a 50mm f1.4. The first grab was shot at f8. Notice the background is just slightly out of focus. The second was shot at f4. The DOF is much shallower i.e., background is much more out of focus. I was able to open the lens up by adding a Neutral Density filter.
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