Shadows don't transfer nicely to H2

[Justin W]

Hello all,

Well, the Mark II camera is up and running and doing as fine a job as I would like,
but it turns out I still have a lot to learn, and just having the right equipment doesn't make up for lack of skill.

I've been burning some transmission shots on 4x5 VRP-M, and transferring the resulting images to reflection H2s.
My "masters" have been shot with collimated reference via an 8" telescope parabolic, and reconstructed for transfer with a collimated beam as well, so focus hasn't been a major issue. Brightness is acceptable, and the images are sharp...

...but my H2s lack "punch"... and I think I've just now realized why: The shadows that looked cool and moody and artistic in my transmission masters simply result in crappy areas of my H2s that don't have much image there.

I remember reading way back when, as I was online teaching myself about holograms, that folks will try for object lighting that seems to come from overhead, as this is more natural for the eye, i.e. shadows will occur beneath features that create shadows. I must have misenterpreted this to mean that shadows are desirable in a holographic image. I'm re-thinking this now as I see how poorly they transfer from H1 to H2.

In fact, I'm entirely questioning the value of any shadows whatsoever in a transmission hologram intended for use as a master to transfer to reflection. I'm hoping to hear opinions from any and all holographers experienced with reflection transfers; do you guys like shadows in your images? Should I work (when mastering) to eliminate shadows altogether via multiple object beams? If shadows considered OK, how to make the transfer to H2 as something other than just a blank spot in the final image?

Please chime in.
Thanks, guys.

[BobH]

Here's an image with heavy shadows. Is that what you mean? His name is "Boris", born in '82 as one of my first images. He projects out from about the ears.

[Justin W]

Hi Bob!

Well, no, not like that - your shadows look good... mine don't. Heheh...

What I will do in a short few moments here is attempt to post photos of both the master (laser transmission), and the transfer (reflection).
Maybe trained eyes can critique and tell me where my issue is?

[Justin W]

The first photo is the reflection transfer

The second is the transmission master

I think I see now what my issue is - I'm not as concerned with the shadows as I am with the places that just weren't lit well when I mastered the image, such as Buddha's chin and the fingers of his raised hand. I clearly need to put more care into my object lighting... Lesson learned!

[JohnFP]

Well Justin, not that your are doing H1 masters you can elliminate the shawdows by turning your object on it's side. Then you can light it with two object beams, one from top and one from bottom to get rid of all shawdows. But you will need to rotate the polarization of you beam to be in the s plane.

[JohnFP]

Another techique is to back you object up away from your plate in your mastering and then set your spatial filter that illuminates the object right next to your plate. That way the object lighting is almost head on to your object.

[dave battin]

its not easy to foresee how these thing will come out, and the best way to learn is by doing (as you are now) Bob's “Boris” works well as we all easily recognize what to expect in the shadows, (from our own experiences of seeing similar objects), Your Buddha has a lot of detail ,which if is in a shadow you cant perceive what is missing. a object as you have there ,i would have at least two object beams with more kickers to high light the under areas. nice work Justin, how long have you been making hologram?

[Justin W]

Hi guys,

I guess I've been making holograms for maybe two years or so (with long lulls during which I was accumulating better equipment)
I started with a holography-inappropriate laser (a multimode CLM module), then upgraded to the microgreen I lase with now, plus my new steel table and a spatial filter and parabolic for my reference and other helpful innovations that have accelerated my progress nicely.

Yes, I shoot with objects on their side and a side reference that emulates top referene in this orientation. I just can't see the need for going literally overhead with my reference beam - that would be a massive amount of equipment to get a parabolic overhead and stable, plus the stress of tending polarization...

So yeahbuddy... I master my objects on their side and will be exploring multiple object beams in the future. I tried this before and it worked OK except I had trouble with the polarization of my second object beam; I use a polarizing beamsplitter for my primary beam split, which gives me a horizontally-polarized reference beam (perfect for my "side" reference), then a vertically-polarized reflected (object) beam. I'm fortunate enough to have a second wave plate to turn this object beam horizontal as well, but then when I split the object beam into two object beams, (with a Cheapo Depot 50/50 cube), only the transmitted beam winds up horizontal.

Poopy.

I imagine a third wave plate would remedy this, but that's starting to sound excessive and frankly kinda decadent. Maybe I could get fancy with mirrors and twist my second beam around some until it's horizontal again...

[jonbrodel]

Hi Justin W

Great subject blessings to you . in correct attitude of respect please make offering . small clean fill bowl of water in front of Buddha . request teaching .

it is dificult to explain . experience will help .

your transfer copy exposure needs to be correct to record efficient hologram.

the image surface you light in the master . is later at or near the surface of the copy.

any bright spot may burn the copy emulsion before an adjacent dark spot exposes.

burns and unexposed areas will not reconstruct efficiently or at all.


It is a difficult art to acheive even light distribution over the image plane of the copy . ideally the image light on the card will be as even as the referencce light . but this is vitualy impossible

imagine the copy films image plane when you veiw the lighted image for mastering.

any bright point (at film surface in transfer stage) will be 100x different brightness just a matter of millimeters forward or back ><

imagine the light exlosure for any given "pixel" area of your copy film (and as it will be slightly forard or back)

you need to light image very carefully to get a bright and clear image copy


droping a single mirror to switch back and forth between master and copy setups . and reshooting masters to fix problems observed from test copy results . I learned a lot.

Good Luck

[Justin W]

Hi Jon,

Thank you for your reply.

I definitely did face hot spot issues on this transfer. I can recall BobH giving a helpful pointer some time back that sounded a lot like what you allude to - that is, try to keep the plane of the H2 (when going for image-planed copy) out of the more brightly-lit areas of the projected image. I think that yes, being more mindful of my intended transfer plane from the onset will help my H2s greatly. Buddha's chest, in the master, was the brightest portion of the image and (mostly coincidentally) wound up being the plane of the H2. This was related only to where I could place my H2 film without it catching H1 reconstruction light. A less arbitrary placement of the H2 film will surely yield better results.

I'm also considering burning my masters with a backdrop that will possibly even out the projected image and reduce the relative hotness of hot spots. This strategy might even reduce exposure time of the masters as the film might see more object light.

But that's idle conjecture... What I know for a fact is that doing a better job lighting my objects when mastering will result in better images after transfer...

...and I look forward to seeing the results of that when I get more film next week!