Guys,

Just want to share that I finished modifying the medium format lens adapter I made for my DVX and made it fit the HD100.

The results were great. I'll just finish attaching the battery housing and I'll post photos or footage.

1st observation is. compared when it was on the DVX, the HD footage from the JVC is much much better. The resolution and low noise quality of the HD100 helped in producing great images.

The problem of lens breathing when racking focus is solved when using a lens adapter.

The shallow DOF is an added "trick up your sleeve" when using this camera which is otherwise hard to achieve.

This adapter is the spinning GG type.

would love to see pictures and footage, well done!

Ok guys,

Here it is,

A pic of the HD100 and DIY DOF120 adapter
http://tedramasola.9k.com/images/hd100_n_dof120.jpg

HD100 and DOF120 mounted on a DIY mini Skater
http://tedramasola.9k.com/images/hd1...ywood_sktr.jpg

A frame grab.
http://tedramasola.9k.com/images/hddof120_frame-1.jpg

If you have problems with the link, go here;
http://tedramasola.9k.com/photo2.html

I have sample footage about 33mb in size, If anyone is interested, please tell me ideas where to post it.

very nice,

please tell us more about your setup, achromats, pcx's distances and such, always useful.

Wayne

The ingredients are, midformat lens > spinning "gg" > 2pcs stack of +4 closeup filter and 1pc +3 close up. > stock 16x lens.

The 3 close up lenses are all 67mm in diameter. I got an 82mm uv filter, removed the glass and used this as a 'holder' or 'step dwn' ring for the 67 mm close ups.
I poured marine epoxy between the 82 and 1 67mm close up.
I threaded the other 2 close ups BEHIND the 1st so when you thread it into the stock lens, the close ups are inside and really close to the first lens element of the stock lens. this avoids any fringe distortion on the image.

I hope I wrote it right..

I'll try to put a link to a construction diagram soon Wayne.

Good work, dont see many adapters coupled to the HD100.

I checked my camera settings and realized my mistake.
Nateweaver, in another thread pointed out the soft image.
The image I posted earlier was too soft because I lowered the detail settings.
Also, I didnt WB after changing to the lens adapter.

The following images were achieved with detail set to 1.
I used Paolo's true color scn file and Tim's gamma settings.

Here are new frame grabs.
from a 80mm:
http://tedramasola.9k.com/images/80mm.jpg

from a 45mm with the camera moved forward to achieve the same framing
of the subject:
http://tedramasola.9k.com/images/45mm.jpg

and without the adapter with the stock lens at full open.
http://tedramasola.9k.com/images/16xstock.jpg

To go to the web page with all the images click below;
http://tedramasola.9k.com/photo2.html

Looks really good. What type of medium format lenses are you using and how are they attached to the front of the adapter? What are you using for GG and motor?

Keith Kline,

Lenses; mamiya645 medium format, 80mm f1.9, 45mm f2.8
Lens attached using the rear lens cap, bolted and marine epoxied to the case.
Motor; 12v replacement motor for CD mechanism, underpowered with only 4.5v battery.
GG; "high tech" frosted CD 'FREE' with a particular brand of CD spindle.(I forgot, think it was maxell)

Good job, Ted. I’m noticing some CA on the back of your hair (yellow) and at the fringe of your arm (blue). Introduced by the stack of close-up filters, probably. A suggestion: it might be worth it to try a reasonable quality achromat.

HTH,

ton of recent experimenting: flip the outermost closeup filter so the thread is facing out. It seems to get the edges to snap back into alignment. Don't know the physics behind why, and don't really care...it cost me $.02 in electrical tape to attach the last filter backwards (or find a F-F adaptor for the filters).

That looks great. I am really impressed with that footage. Nice job.

Heres some grabs from a commercial using this adapter.
This was shot at f 1.9

The flange depth for mamiya 645 lenses is 63mm do you have infinity focus? What focal length are you using to hit the CD? This thing is shorter than most other 35mm adapters and with MF lenses no less. Nice work.

Charles,
Thats correct, the flange depth is 63mm depth.
Yeah, I do have infinite focus.
Among the 3 lenses I have for the adapter, the 45mm has the shortest MOD at 50 cm.
I positioned the GG in the same distance from the actual film plane so i get the same footprint as on the 120 negative.
You can even use the focus marks to get focus if need be.

Ted

You are definitely on a winner with your arrangement. With a 120 format sized image, you should be in front for resolution, even with a Maxell blank.

I second the achromatic dioptre suggestion. Your images are well sharp enough. The colours will probably look even better in a highly contrasted, finely textured image if you ca get rid of the CA.

Very well done.

Thanks for the kind words, youre right Bob, but from where i am located its so hard to get hold of an achromat, I need a +10. Right now its a stack of 3 close ups which produce those CA at the sides. I know they are there, and I know that the close ups are causing it, but i have to shoot with what i have till i get a good close up cause my projects all piled up.
I tried removing one from the stack and the CA was negligible but i can see a vignette so i compromised.

Ted

Is the grain from the focusing screen or gain on the camera? It'd be nice to see a better achromat on this thing, the edge-to-edge sharpness is painful.

Ben, the grain is from the spinning GG. Yeah, I wish I had a good achromat too. The CA is agravated in areas of contrast near the sides.

Ben,
Heres a frame from a well lit shot. Theres minimal grain in this shot.
I think grain is aggravated by lower exposures. But i never use gain with the adapter to minimize the grain.

Ted, cinevate.com is selling a nice +10 achromat. Talk to Dennis Wood about it.

That guitarist shot is so damn sharp! Get rid of the CA and figure out the bokeh, and you've got most of the adapter market beat!

Ted.

The Maxell disk you use now, - is it opaque all the way through the thickness or opaque just on one surface only? If it is opaque all the way through, you might discover a little more sharpness and contrast with a disk which has a surface groundglass finish on one face.

To get the full wide image area without corner falloff in brightness with a surface finished groundglass, the grade of the surface finish might need to be a little coarser than for the 5 micron finish I use on my disks and other builders also use on 24mm wide movie frame versions.

Medium format is a frontier I haven't visited so don't pay much heed to my comments.

I believe Wayne Kinney found his disks for his SGPro at Knight Optical in the UK. Maybe he will add some info here on reading this.

Bob, they are opaque only on one side. and its the one i faced towards the mid format lens.

Thanks Jon, i'll check on it.

I took Jons advice an got in touch of Dennis Wood of Cinevate, he shipped me his achromat and it solved a lot of my adapter's problems!

Im testing it today and below is a chart using 80mm mamiya 645.
f1.9 on the mamiya f2 on the hd100. image size on gg is still 45mm across and 25mm high.

If you're using a Cinevate achromat, then something else must be causing the chromatic aberration (jpeg compression? HDV? Camera settings?). I've never had that degree of CA in the center of the frame.

Ted


To my eye, the fringing on the lines in centre looks a bit like a codec compression artifact although it may be the beginnings of a chomatic abberation.


Optically there seem to be three issues.


There is a small barrel distortion with sharpness falloff into the corners.

There is chromatic abberation towards the horizontal edge thirds of the image.

There is a third chroma issue which is not symmetrical across the image.


The centre fringing is not something I would get heartbroken over.


The barrel distortion is something I would expect to see. Medium format relay is uncharted territory.

Dennis's acromat will have been optimised for a smaller area image off the groundglass and your arrangement may be reaching into areas of the lens we would otherwise not see. I will comment furthur down in this message.

The chromatic abberation in the edge thirds is probably linked to the barrel distortion.


The third chroma issue is unusual. It may be simply mixed colour temps of separate lighting sources onto the chart, colour variance across the chart itself if printed with a colour printer on photo paper ( I had this issue myself )


If the chart and its lighting are okay, then it may be created by

axial offset of the optical centres of the lens on front of the adaptor and the camcorder optical centre,

angular misalignment of the lens on front of the adaptor.


Both of these individually or in combination would introduce an assymetrical defect.


Another possibility is offset of the achromat dioptre centre-axis relative to the camera optical centre axis.

Unless you have mounted the achromat separately to the relay lens and not by threaded step rings, I doubt this is an issue as the dioptre and camera optical centres are created by some precise machining and die making.


My first experiment would be to make a spare groundglass and install it, maybe lay a clear panel over the existing groundglass if you don't want to disturb it, view the projected image by eye and mark clearly on the spare groundglass, the outer edge of the image circle and the precise centre of the image circle.

Across this area I would also draw a checkerboard of crossed straight lines.

I would then fit the adaptor up to the camera without any lens fitted on front of the adaptor, light the groundglass through the lens hole and study the camcorder image of the lines and centre mark.

You will need to lock the groundglass disk from moving with a piece of adhesive tape on the clear face of the disk which you can clean afterwards without damage.

This will show if the barrel distortion and asymmetric colour shift is a charactistic of the front lens, and if it is correctly centred.

You could do this with the front lens mounted and imaging a plain white background but you won't be able to identify any added CA caused separately by the lens if it is attached.


My second experiment would be to move the adaptor furthur forward, almost to the distant or infinity end of the focus limit of the relay lens/achromat. This will result in a slightly larger area visible off the groundglass but might reduce the distortion.

If the defects are projected by the front lens onto the groundglass itself, then the defects will become more apparent.


I am unclear if you are using the JVC standard lens with the achromat on front for your relay.

If the Mamiya f2 you refer to is your actual relay lens used like Quyen's Minolta lens and has replaced the JVC standard lens then much of my following comment is disqualified.

This lens if used for relay, could cause you some edge falloff, chroma problems and distortion as it is not optimised for 3 x CCD imaging. Getting correct backfocus of this lens may also be a problem task if you have made a custom mount or spacer-adaptor ring to marry the lens to the JVC mount.

My third experiment would be to attempt to place Dennis's achromat closer to front of the relay lens if possible.

You might need to dismantle the optical element of Dennis's achromat from inside its ring to do this.

If you are using the JVC standard lens then you will discover that the lens focus movement changes the distance between an achromat mounted in the thread of the fixed lens hood mount and the front element of the standard lens so this experiment is worth trying.

I found it necessary to mount my own achromat directly to the JVC lens barrel itself to avoid this problem.

Dismounting Dennis's optical element from its ring could be risky so I don't encourage it.

If the barrel distortion becames worse the achromat may need to be placed furthur forward with a thin spacer washer on the threaded shoulder and maybe a spacer in the ring around the element in the acromat to take the element furthur forward.

Too far forward and the image may develop a pincushion distortion. all of this interacts in combination with variations in lens focus and variations in the distance between the groundglass and the front of the camcorder relay lens.

If you can successfully fine tune in this area, you may also pick up a bit more sharpness.

In the JVC menus, you may find a colour correction function which deals with broad area colour variation across the image caused by individual lens characteristics.

Many broadcast cameras have this adjustment and the setting is saveable as a scene file, personal preset or suchlike. The JVC KY-F50 camera head has this feature so your JVC may have it as well but I don't know what it will be called.

Your image as it is I could quite happily live with. I would tend to compose my shots to avoid areas of high contrast fine texture in the horizontal edge thirds of the image.

LATE FOOTNOTE:

I observe on yout previously posted image of the man and guitar, a darkened area on the right side of the image as viewed which suggests your front lens may be offcentre also to right of camcorder optical cetre axis if you are not flipping the image uprigt into the camera. I had not previously observed this.

You may need to consider using a slightly longer focal length prime lens for your relay lens and taking a smaller area off the groundglass to get inside the otspot and also the soft areas if they are relay lens related.

Bob,

thanks for taking the time with your assesment. I continued with my tests and found out that the sweetspot for this setup, escpecially using the brevis achromat is much smaller than 45mm width of the image. The sweetspot without corner distortiona and cA is actually close to a 35mm. I am basing my test on the mamiya 45mm lens since wide lenses tend to exhibit more of the vignette and distortion on the corners.

i'l try to see how much i can get away with as far as edge distortion, i'll try to get a balance between clean edges and a wider gg image. Im hoping to achieve lesser grain by a larger image.

With this observation, does it mean that 35mm adapters are actually capturing less than 35mm image width on the gg? Or is it exactly that?

Ted

Ted

You pretty much have it right in regard 35mm adaptors.

An image width of 22mm to 24mm is more typical and closer to the 35mm motion picture film image width. Some do wider. So in proportional terms, your arrangement seems to be performing much the same but yielding a larger therefore potentially sharper image.

48mm will be outside the medium format sweet spot of 36mm x 36mm for groundglass relay.

You can cheat a little and frame a bit of defective image into the lost area around the TV "safe area".

Bob,

I did some realignment and found a lot of improvemnt in sharpness and vignetting. The alignment proces is on a per millimeter basis and is so tedious, this might never get perfect for me, i wanna stop at a point where all my lenses can be usable and without to much vignette and corner softening, especialy with the wider lenses. I moved back my jvc farther from the adapter, and still using the stock lens at a setting of around 20 and full macro.
The brevis achromat is still attached with step down ring.
I posted some grabs with subjects near the corners and top and lower edges to gauge the corner and edge areas areas.

First two images from mamiya 645 45mm f3.5 and the diagonal guitars by an 80mm f1.9.

Ted

Ted.

I think you about have it beaten. I could live with what you have there. No corner falloff observable, a nice look, maybe a little chroma margin on the high contrast edges but I understand JVC's own lens also does this so there may be no improvement remaining for you to make.

We have the advantage of dissecting your still frame grabs over lengths of time. A motion image which directs audience concentration upon a well shot subject will steer attenton away from any chroma margins on contrasted edges.

On a big digital projection screen it may be a different matter, but those are not always all that sharp anyway.

I might be tempted to take the camera back from the groundglass a little furthur and zoom in to compensate to try and get away from using the JVC lens own macro feature as well as having the achromat on front.

In my own tests with the JVC standard lens and a 7+ dioptre, I tried using the JVC backfocus adjustment or the macro adjustment just to be able to pull the groundglass physically closer to shorten the appliance itself.

This gave me a poorer image, it did not hold focus through the zoom range and there was a CA issue, so I put another 15mm back onto the length of the tube I was using and zoomed in a little more.

If you can keep the backfocus neutral, then you have the advantage of a little zoom range to help with framing and composition. You won't experience the same resolution hit this practice introduces with 35mm adaptors.

I think you should be well pleased with what you now have. It is certainly usable. Put a hold on your developments for a little while and just go out and enjoy shooting with it.

While you are shooting or simply doing other things, you will still come up with ideas. Given a few weeks of ruminating and digestion, the ideas will be easier then to put in place.

Bob,

Thank you for your help in providing me with tips on the alignment. Your right, i'll give it a rest now and do some shooting. Im posting a pic on the adapter modification.

Ted.

You made the time on a developmental prototype when others including myself would rush things, to file the sharp corners and tidy spacing of screw centres and add extra right-angle bracing to avoid any shake or mechanical loading of the camera structure.

The decals and focal plane mark add to the presentation and perception of competence by clients.

Your work seems to be thorough and unhurried.

Very impressive. I would hope your imaging work, likely as thorough as your project, yields appropriate reward for your efforts.

Enjoy.