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Old January 28th, 2005, 09:27 AM   #16
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Again, Bob, thank you for the most thorough and passionate posts! I don't know what I would do without you!

Ok, so if I am to understand, I can achieve this 'rack focus' - and I am using the term very loosely because I couldn't achieve a semi-amount of it with my 'DV -PV852' but because it is a digital focus ring, I could never really focus pull or rack focus effectively. Back to the topic - I really have to find a way to support this monstrosity of a lens to the housing when I build it - ESPECIALLY since that is where the focusing the piece.

1) Now, are you saying I can achieve this 'rack-focus' or any kind of focus using the barrel of the macro lens (pulling it towards the action and back towards me)?

2) Now this is presenting a new challenge to me. I have used 16mm bolex's before, it they really don't have a great focus range - this is starting to sound like this - I have to really plan and set up the shots to make sure they are in focus before I pull the trigger whereas with my MiniDV, I could put the camera anywhere, zoom and focus - am I making the correct parallel with the 16m on this one?

3) Again Bob, how do you determine the correct focal length from the GG? Is it trial and error or can you determine it from the type of lens?

4) Last one, (for now ;) ) - is it better than to start with the macro lens telescoped or compacted when setting the focal length?

Thanks again for all your help! I am getting more excited about this everyday!
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Old January 28th, 2005, 02:41 PM   #17
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I think you'd be much better off if you forget about the macro lens, because it's not meant for this. Like I said before, a very good photo lens which can focus with a separate ring will cost almost nothing, maybe you know someone who will give you one.
You'd better use the macro to put it on your DV lens and focus it on the GG.
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Old January 28th, 2005, 02:48 PM   #18
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I've said many times, macro filter, not lens. It's not sinking in.
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Old January 28th, 2005, 03:03 PM   #19
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Ok, I hear you - but after a few tests, I am focusing pretty well on the GG using only my mini DV. I am going to use the Kiron in front of the GG towards the action when I build a semi-rig for further testing.

As for findering macro filters, I have checked - 3 stores and 4 photographers - and they all won't give them up or have them (and I did offer to pay). So it is not as easy as it sounds (unless you want to send one my way!)
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Old January 28th, 2005, 04:49 PM   #20
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Sorry, I'm confused. I thought the Kiron was the macro, because you say 'KIRON MACRO' somewhere. You don't need a macro filter in front of the DV, I just said that because I thought the Kiron is a macro filter. I don't use a macro, because the DV is fine without.

The images look good in your tests, but also try it on a far point, at least 15 meters.
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Old January 28th, 2005, 05:50 PM   #21
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I will do that.
Yes I have a MACRO Lens (the 6 inch tube barrel) but NOT a macro filter. When I did the test, it was without a macro filter on the front of the DV (I had actually stacked Binocular lens, which is why it looks a bit dirty). I was thinking that I won't need the MAcro filters, but if I can get one for the FRONT of my DV camera - for cheap, I will pick it up.

Going to test 15m + tomorrow and send results.
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Old January 29th, 2005, 01:30 AM   #22
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Mandy.

Questions answered by number rder asked.

3. To set correct backfocus on your zoom, for an Augs it is about makibng sure the back face on the mount is exactly the same distance from the rough surface of the groundglass as it would be from the film in a film camera. If you don't have the camera your Kiron came from, maybe go to a pawnshop or camera store and ask to check it against some of their stock. The ebay posting suggested Yashica. Some after-market manufacturers limit themselves to specific camera types, others cater for many like Tamron do.

Once you find the camera it fits up to, look for the "O" mark which has a "-" through the center of it. That represents the film plane of your camera. It's either on top near the rewinder or beneath, again near the rewinder on most types.

Found it?? Okay. measure from the "-" mark, forward to the front face of the camera lens mount where the lens itself buts against it. This measurement is often referred to as the "flange to focal plane distance". Whilst at the camera store you might enquire if it is possible to buy in the piece for the camera which mounts the lens. (Unless a camera is comprehensively stuffed, I have an aversion to ripping something to pieces just for the part I want.) Now you know that distance, you build your Agus case so the lens mount is the same distance fro the rough side of the groundglass.

If you can't get your hands on a camera, the next step is to look for a table or chart on the web which described the flange to focal plane or backfocus distance for particular lens types. It's been posted here before on dvinfo but too far back for me to search for it with a 720 bytes (yes bytes) per second overhead copper pair landline.

If that's no good, the next method is a precise and tiresome one best left to a camera specialist with the right equipment to tackle. That said, a rough decription follows of the method. It means fixing your lens onto a frame, measuring from a point about 45mm behind the mount face, forward to a target of some kind, the easiest is a brightly lit test chart but a newspaper with some felt pen marker lines across and down it like gunsight crosshairs will do, also brightly lit.

Set your Kiron zoom ring or slide midway, about "50mm" should be okay. Make sure the "macro" function is selected "off". (Ref. Question 4). On some lenses with a slide zoom, the "macro" function is set "on" or enabled by pushing the zoom beyond a pointnof resistance then twisting the barell when a faint click or locking action will be felt. The lens then stay in "macro" mode all the way back through the zoom range until the zoom is again pushed to its limt and the "macro" function deselected by twisting the end the other way. To understand this you really need to find an operator's manual for that lens as the manufacturers have not really shaken down to a common stnadard on that one.

Rotate the focus ring on the lens or the front barrel if that is the way is works, so that the feet or metre number on the ring and the dot matches the distance from the 45mm point behind the lens to the target you have set up. You will have to fiddle and fuss shifting the lens back and forth until you find a number on the lens focus ring which matches up exactly to the distance. Once you have got that, use a very strong magnifier and look at the image on the groundglass. Move the groundglass closer or furthur from the lens mount until the image is at its sharpest. You may have to fiddle and fuss some more with the distance from the target. OKay you've done that but the fat lady is still clearing her throat. Now try zooming in on the target. Does the focus hold? probably not. Zoom to back to wide. Does the focus hold? probably not.
The more fuss and fiddling until you can get focus to hold through the whole zoom range. Once you have got that working, you have a useful flanage to focal plane distance to build to. We are talking about fractions of a millimetre at the film plane or groundglass. For this to be successfuly done with rough home builds, it is simplest to wrok to the known flange to focal plane distance then to build an adjustment into the case to allow the groundglass and the motor to be moved back and forth with fine screw adjustments to take care of build errors and to allow for inclusion of a condenser or two if you later choose to go that route.

This fuss and bother is one of the reasons why prime lenses are better than zooms as well have having sharper resolution anyway. As long as you can get an infinity focus with them you can get an acceptable image.

1. In your Agus there are TWO focus functions.

(a) primary or objective focus (Kiron lens).
(b) relay focus. (Camcorder to groundglass).

Focus (a) is the one you move to get "rack" focus as you put it. You don't move the front of the lens back and forth. If this happens on your Kiron lens then it is more likely to be the zoom function. If sliding the front back and forth uncovers little lines with numbers like 28, 50, 75, 120, beside them, then this is definitely a zoom function.

Focus numbers usually run from single figure to about 30 then end with an infinity mark which is like a number "8" resting on its side. Whatever control on the lens adjusts these numbers is your focus adjustment. It is likely to be operated by rotating a ring or the front section of your lens.

Focus (b) which is your relay or camcorder focus, you set to view the groundglass sharply, then leave alone unless it drifts out of focus. After yuo have built your Agus, if your camcorder is image based autofocus only, set your Kiron lens aperture to manual, then set the ring to f11 or f16 and place a white paper sheet which has no texture on it in front of the Kiron lens but not so close it blocks off the light. Your viewfinder should only be able to see brightly lit white paper. The autofocus should then see only the groundglass texture and lock onto that and not try to look through the disk. Do your white-balance ajustment at the same time. Set your Kiron lens to correct focus for the distance from subject, open the aperture to its widest which will be f4-something, pull the paper sheet away and the autofocus should hold. Start the disk, adjust the Kiron focus visually though the camcorder like the Bolex (Ref question 2), then press the run button. It takes practice to get the rhythm. If your camcorder has a manual focus over-ride then use manual focus to set relay focus or use the autofocus to set then lock it off by switching to manual. It is good practice also to stick masking tape over the camcorder focus and zoom controls one they are set correctly as they are easily bumped and can spoil a critical shot.

If the camcorder has an ultrasound based autofocus adjustment then none of this method for relay focus will work. I suspect that ultrasound is not used if yours is a recent camcorder model, otherwise manual relay focus of the camcorder is your only option.
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Old January 29th, 2005, 10:29 PM   #23
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Thanks Bob (again!).

That chart thread I found, but the link is down - so much for that. I am starting to look at purchasing lenses from the pawn shop to make things easier - what you told me, is a little confusing - I was hoping to eyeball this thing, trying to get the focal flange by moving it back and forth, but I don't think that is going to work. I saw the housing that consists of threaded bolts so as to make the tiny moves easier, so I might try that. Right now, I want to do some more tests.

Let me ask you - if I am focusing on the GG with my DV, is it best to focus the MACRO LENS on infinity so I can get the longest focal range? (like when you set focus for a camera). The reason I am asking is because if I set my DV camera to focus on GG, what am I supposed to be trying to sharpen - the foreground or the background - or just the entire thing?
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Old January 31st, 2005, 06:22 PM   #24
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After many more test, I am discovering that being precise is very important (like you said). A friend of mine has some 35mm lens which I am going to take a look at tomorrow.

Now for the housing on this machine - the more I test it, more it seem like a monstrosity - are the other machine this big? I remember hearing that AGUS used a 25CD spindle cover, is this true? Mine seems alot bigger than that, leading me to think maybe I am still doing something wrong,

Right now I am using two stacked binocular lenses to simulate a macro filters until I can get one. I can zoom in and not seen any vignetting - and this is without having any housing on it at all - in complete light. I still have to test more than 15 meters like someone already pointed out, but tests are proving to be better than I expected. I guess building the housing is the next step, but I really need to figure out the focal flange (that thread with the chart is there, but the URL for the chart is no longer available). So I guess it is back to the drawing board or getting another lens, unless someone can think of a way to measure this without alot of problems.

Thanks
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Old January 31st, 2005, 06:50 PM   #25
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I still don't understand why you use a macro filter (binocular lenses in your case)
It's a simple system, a 35mm lens, about 45 mm space, maybe a condenser lens in that space, the ground glass and than the DV camcorder filming the center of the image, which is about 35mm wide. There is some website with an illustrated guide, but I can't find it.
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Old January 31st, 2005, 07:07 PM   #26
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Ah! Here it is:

http://www.mediachance.com/dvdlab/dof/index.htm

It's 5 pages, be sure to click on 'next'
Is it from someone on this board?
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Old January 31st, 2005, 07:31 PM   #27
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Already been there and back, its a great website!

I don't have a condenser - without the macro lens, my DV camera cannot get in close enough to eliminate Vignetting, so that is why. If the condenser fixes this problem, I will go for it!
I know what you are saying and maybe I am doing something wrong, I guess it will take some more testing.
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Old January 31st, 2005, 10:15 PM   #28
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Replying as asked again.


I was hoping to eyeball this thing, trying to get the focal flange by moving it back and forth, but I don't think that is going to work. I saw the housing that consists of threaded bolts so as to
make the tiny moves easier, so I might try that.

----- You need close-up eyeglasses or a magnifier of some kind to look at the projected image on the wall. You could buy in two project boxes and make up one just for testing purposes. You could then use your cam to do the magnifying for you so you can best position the Kiron lens.

Let me ask you - if I am focusing on the GG with my DV, is it best to focus the MACRO LENS on infinity so I can get the longest focal range? (like when you set focus for a camera).

---- Infinity is okay as long as your Kiron lens is viewing a target which is a very - very long way away. It would probably be the best way yo do it anyway, BUT -- In most household workshops you can't get far enough away from the target

The reason I am asking is because if I set my DV camera to focus on GG, what am I supposed to
be trying to sharpen - the foreground or the background - or just the entire thing?

----- Looking at the groundglass with the DV camera is the "relay focus" stage. All the DV camera has to be able to do is see the image area of the groundglass texture completely and clearly, no more than that. (Focussing the image itself is done by adjusting the focus on the Kiron lens.)

Objective focussing stage :-

Subject >> operator focusses Kiron lens >> Image arrives onto groundglass. Parts of it are sharp, parts are out of focus as the operator has chosen to make them look.

Relay focussing stage :-

Image has arrived onto groundglass >> Camcorder sees image. >> Camera operator adjusts camcorder zoom to frame image and adjusts the camcorder focus until the sharp portions of that flat image are as sharp as they will get.

Look up the P+S Technik website for their Mini35 operator's manual and Pro35 operator's manual which are there as .pdf files. Their method of setting the relay focus is valid for the Agus35.
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Old February 1st, 2005, 06:14 PM   #29
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Thank again and again Bob. I actually came across a new lens today, which maybe will be better and easier to set.

It is a SIGMA Zoom 1:35~4.5 f=35~105mm

Maybe this might be better for use. Right now I am still experimenting. I am going to set up a box, just to see what happens - a prototype for now. If it works, I will build another better model, but it helps to have people like yourself on board to give assistance!

So what do you think of this lens? Is it going to be a better fit than the KIRON MACRO?
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Old February 1st, 2005, 09:47 PM   #30
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Did some tests tonight and found out I am way too unprepared for this yet - used some canvas board for painting from the $1.00 store and created the holder for the Lens and the Ground glass - the lens is ultra heavy, so I had to prop the piece up with something at the front to prevent it from toppling over (and this made it hard to focus with the lens). After I put the two pieces together with carriage bolts and tried to adjust to focus and found that it will work better with particle board and bolts with screw heads so I can fine tune with a screw driver. Also, I realised doing this at night is not the best time.

Also, a question I forgot to ask -
1) when focusing on infinity (to try and get the full focal range), do I just turn the KIRON to the little 'infinity' icon on the lens?

2) Do I leave it compact (as apposed to stretched out or telescoping)?

3) When destroying the CD player (right now I am using a motor from a toy), do I just need to keep the red and black wire and get rid of everything else (like the copper ribbon that is attached to it)?

Thanks again so much!
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