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Old March 12th, 2005, 03:01 PM   #1
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Macros- is stacking better than single?

I am trying to decide whether to return the 7+ 10+ macro and get a 1+2+4+ macro combo, but I don't want to return it if stacking (1+2+4=7) is not a good idea or ends up with less quality. Has anyone had any experience with this?
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Old March 12th, 2005, 06:42 PM   #2
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Stacking is no different than using a single lens of the power you are looking for. It's actually worse to stack because you're introducing more glass into the system.
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Old March 12th, 2005, 11:51 PM   #3
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Definitely do not substitute stacked macros (close up lenses for a single lens of the same power.

If that single lens is a one-piece glass, then you might need to move up to an achromatic dioptre, which is two pieces of glass in a mount. With that, radial distortion in the image and unwanted rainbows should go away.

If you want to get some money back on unwanted glassware, I would favour returning the 10+ as this is too powerful for you to be able to easily fit a simple right-angled prism path in between it and the gg. If both are single glass and not two-piece achromatic dioptres, then if both are identical quality, I would favour the +7 over the +10 as the edge distortion and rainbows will be less.

The +7 is going to give you a device which sits about 120mm out from your camcorder so you will likely need rods/rails. +10 is not going to bring it much usefully closer.

Your resolution limit seems to be a combination of three factors :-

GG seems it may be too diffusing. Are you still using the stick-on?

The gg area being filmed seems on the face of it to be too large. You may need to zoom closer. This is going to cause problems with an unsharp gg but will remediate deficiencies in the macro (close-up lens) and vignetting as you will be shooting more through the centre of it.

There appears to be radial edge distortion and softness which may be related to use of a single element close-up lens (macro). Again zooming in closer on the gg may fix this somewhat.

These three factors will be all combining to limit resolution of the whole system. In order of priority, I would favour making a finer grained gg to 5 micron AO standard, then go for the two-element achromatic dioptre of +7 power if the edge distortion remains a problem when you zoom in a bit closer.

For the authentic reproduction of the motion picture 35mm 4:3 frame, your target area on ther groundglass is 24mm wide by 18mm high. A 5 micron AO equivalent dressing of the gg surface should give you at least 500 TV lines of horizontal resolution at that magnification. This is acceptable for prosumer standard definition MiniDV/DVCAM which apparently hits a wall at 530TV lines.

The texture of the gg should be fine enough that you can almost see sharply, a strong light through the gg when trying to see through it by eye.
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Old March 13th, 2005, 10:28 PM   #4
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Bob, what about HDV?

Bob, you seem to be quite knowledgeable on the subject of the 35mm adaptor (like, yeah, that is like the understatement of the century)

I'm curious - what do you think is the potential for 35mm adaptor working with new HDV format from Sony? 1080i...

One thing that excites me about the Sony is the tremendous lack of grain under low light conditions - so if you happen to have a system with a lens that's "losing" a lot of light, maybe you'll still luck out in terms of final image...

Just eager for your thoughts...
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Old March 14th, 2005, 06:27 AM   #5
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Mark.

I tried mine out on a HDW750? at a rental place here in Perth, - free plug for them if it is permissable - Location Equipment in Leederville Western Australia. Admittedly it was my PD150 rig hand-held in front of the HDCAM's own zoom lens, but the result did not look very encouraging.

With a proper dedicated relay lens like the Mini35/Pro35 one could expect a better result but I suspect most of the home-brew groundglasses are not going to perform well enough for sharpness.

However the HDCAM codec may cope better with the random grain effect one sometimes sees from one individual frame to the next. With MiniDV / DVCAM, these seem to manifest as 4 - 16 pixel area blocks of artifact across the entire image, mainly in areas of even light shading.

My suspicion is that the MiniDV / DVCAM codecs may struggle with the massive amount of small-scale variation across individual frames and start to average things out across larger areas to maintain the frame rate.

This stuff is way outside of my technical knowledge and ability to make commentary on and I might be unjustly maligning the MiniDV /DVCAM systems in the process.

HDV may perform differently as a whole new generation of digital processing may be going on which can deal with a lot more data before committing the info to tape. Unfortunately, the new cams have a 72mm filter mount and larger diameter front element so I can't just try my version on front of one for any valid comparison.
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Old March 14th, 2005, 11:53 AM   #6
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<<<-- Originally posted by Bob Hart : Definitely do not substitute stacked macros (close up lenses for a single lens of the same power. >>

Thanks for the info on that one. I am going to stick with the 7+ 10+ (unfortunately they came together as a package so I can't take one back with taking both back).

<<If that single lens is a one-piece glass, then you might need to move up to an achromatic dioptre, which is two pieces of glass in a mount. With that, radial distortion in the image and unwanted rainbows should go away.>>

The guy at the camera store told me to use a PL filter to get rid of the colour separation, so I am going to try it. As far as a Achromatic Dioptre, I am also going to look into that as well.

<<The +7 is going to give you a device which sits about 120mm out from your camcorder so you will likely need rods/rails. +10 is not going to bring it much usefully closer.>>

I have already built a set of rails for testing. It works ok, but I am more concerned about getting rid of the blurring around the edges.

<<Your resolution limit seems to be a combination of three factors :-

GG seems it may be too diffusing. Are you still using the stick-on?>>

I am using the Press and Seal, but have gone back to the Frosted GG/CD to see the difference and they are negliable.

<<The gg area being filmed seems on the face of it to be too large. You may need to zoom closer. This is going to cause problems with an unsharp gg but will remediate deficiencies in the macro (close-up lens) and vignetting as you will be shooting more through the centre of it.>>

I guess that is the problem I am having with this. I am zoomed in as far as I can go right now. I also have to pull the camera back a little ways so I can still focus and therefore I am getting some vignetting. Seems I fix one problem to be presented with anothyer.

<<There appears to be radial edge distortion and softness which may be related to use of a single element close-up lens (macro). Again zooming in closer on the gg may fix this somewhat.

These three factors will be all combining to limit resolution of the whole system. In order of priority, I would favour making a finer grained gg to 5 micron AO standard, then go for the two-element achromatic dioptre of +7 power if the edge distortion remains a problem when you zoom in a bit closer. >>

I would love to make a better GG - but until I can find more of the CLEAR CD's (not the greenish tint, the clear ones seem to be almost impossible to find lately) and learn how to make them properly, I have little recourse but to stick with what I have (no pun intended).

<<For the authentic reproduction of the motion picture 35mm 4:3 frame, your target area on ther groundglass is 24mm wide by 18mm high. A 5 micron AO equivalent dressing of the gg surface should give you at least 500 TV lines of horizontal resolution at that magnification. This is acceptable for prosumer standard definition MiniDV/DVCAM which apparently hits a wall at 530TV lines. >>

I am waiting for some Transparent Foil to come in the mail. I am going to try that and see what happens. but besides that, I was hoping someone would come up with a production of CD GG's that could be sold to people like me!

<<The texture of the gg should be fine enough that you can almost see sharply, a strong light through the gg when trying to see through it by eye. -->>>

When I look through the GG by eye, everything looks great, with a magnifying glass it looks good as well, so that lead me to believe it was
1) my camera
2) the macro lens
3) the hotspot therefore a condenser was needed

I didn't think much about the GG because it looks good when looking through with my eye.
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