Having issues with medium format slide projection.

[sruddy]

I'm having two issues:

1. Visible Anti Newton pattern
2. Image degradation after about 15 seconds

My equipment:

1. Rolleiflex E3
2. Rolleiflex T
3. Fujifilm Provia 100F (will be experimenting with all available transparency films.)
4. Rollei P66S Projector (restored with new lamp)
5. Rollei Schneider AV-Xenotar 2.8/150 HFT (NOS)
6. Rollei Vario - Heidosmat 3.5/110-160
7. StewartFilmscreen Studiotek 130 gain 1.2 94" diagonal
8. Gepe AN Glass mounts

My viewing distance is 12' and the image size is 43" (would like to get closer for a bigger image, pattern still visible at 16 feet.)

So my image capturing may need a bit of work to see the sharpest images with highest detail but this is a given.

What I'm not getting is why the anti newton pattern is so visible and distracting. During my projector research phase I saw no mention of this and nearly everyone suggested using glass mounts. Not only am I seeing the pattern if I leave the slide in longer than about 15 seconds certain areas will form a worse pattern that grows the hotter the slide gets. The projectors fan system is working as new, and the inside of the projector is spotless. The slide mechanism is holding the slide firm as well. I would try plain glass mounts but don't see any available. I'm using Gepe AN glass mounts which the grey half is plain glass. I could trash the AN white half and get 10 mounts instead of twenty however they are very expensive already. So I need two solutions and I will modify the cooling systems if that's what it takes to solve number 2. Any type of AN visibility anywhere is totally unacceptable to me. I

 

[AgX]

A guess of mine: moisture from the emulsion evaporating due to radiation, the next moment condensing at the cooled panes.

 

[itsdoable]

It's been a while since I projected medium format slides, but I do remember getting Newton rings once in a while.

AN stands for Anti-Newton, or Anti-Newton rings glass. If you remove the AN glass, you will very likely have Newton Rings on all your slides. AN glass has slightly irregular surface which you can see, and is not optically smooth. It does degrade the projected image a tiny bit.

Newtons Ring is an interference pattern, where the air space between the film and glass is on the order of a wavelength of light, and as the space increases, the interference cycles between constructive and destructive - or light and dark.

Film has an emulsion side, which is rough (relatively speaking) and the polyester base side, which is optically smooth. It is this optically smooth polyester side that created Newton Rings, The Glass slide mounts only have one surface with an AN treatment, which should go on the non-emulsion side of the film.

The emulsion side's irregular surface is not likely to create Newton Rings on a smooth glass surface, so no need for AN glass on that side.

Check the direction you have your slides in the mounts.

Degradation: do you mean the image degrades due to Newton rings, or the image goes soft? Increase in Newton rings happens as the film warms up and curls, changing the Newton's ring pattern. Out of focus occurs when heating the slide moves the registered position, and can be corrected by re-focusing. Leaving the refocused position means you cold slide start out soft, and sharpen up in a few seconds - this is usually only an issue with non-glass mounted slide (hence the glass mounting).

...Any type of AN visibility anywhere is totally unacceptable to me...

I assume you mean to say that you do not want to see Newton's Rings?

or are you talking about the irregular pattern on the AN glass being projected on the screen? In which case, try tweaking the focus so the AN surface is out of focus keeping the emulsion in focus.

 

[etn]

The previous posters are 100% correct.

Just to be sure everything is ok with the projector or screen, have you tried projecting:
1) no slide (or a non-glass mount without film in it)
2) an empty glass mount
3) a slide in a non-glass mount

If yes, what are the results? do they change after a minute or two? (if yes it can be a hint for condensation as AgX said)

I’m pretty sure you do this correctly but just in case: The order for mounting slides into GEPE mounts is: the black side facing the screen; then the film with emulsion side facing the black side; then the white side of the mount.

Hope this helps

 

[guangong]

Very good correct answers. APUG to the rescue!

 

[sruddy]

Thanks for the replies. I was hoping for more definitive answers like you will always see the anti newton pattern in certain areas of an image or I never see the pattern so you must have a bad batch of slides.

A guess of mine: moisture from the emulsion evaporating due to radiation, the next moment condensing at the cooled panes.

Sounds like a real possibility however I'm not getting the process. If the slide goes in cool the first thing to heat is the glass then the transparency. What cooled panes are you refereeing too?

It's been a while since I projected medium format slides, but I do remember getting Newton rings once in a while.

AN stands for Anti-Newton, or Anti-Newton rings glass. If you remove the AN glass, you will very likely have Newton Rings on all your slides. AN glass has slightly irregular surface which you can see, and is not optically smooth. It does degrade the projected image a tiny bit.

Thank you, so there I have it. The pattern can be seen and most people don't seem to mind the degradation. I was hoping for a fix so I have to decide what type of image degradation I can accept, if any. So I seem to have 3 choices.

1. Use AN glass slides and accept the degradation caused by the pattern.
   
2. Use Non AN glass and accept Anti Newton rings
3. Use plain mounts and manually focus after each pop, accept the extra work, and see how bad edge to edge sharpness suffers.

At this point I'm very disappointed. After hearing so may rave about medium format projection I was expecting to be blown away. When I view 35mm slides I have none of these issues. Granted the size and resolution is smaller, however there is nothing degrading the image quality. I'm using a Kodak Cavalcade projector which pre heats the slides, so no popping, and the lens is keeping edge to edge sharpness. The slides are also mounted in metal frames that
keep them consistently flat.

Degradation: do you mean the image degrades due to Newton rings, or the image goes soft? Increase in Newton rings happens as the film warms up and curls, changing the Newton's ring pattern. Out of focus occurs when heating the slide moves the registered position, and can be corrected by re-focusing. Leaving the refocused position means you cold slide start out soft, and sharpen up in a few seconds - this is usually only an issue with non-glass mounted slide (hence the glass mounting).

Neither, I only put one transparency in a plain glass mount. I made it with the two plain glass grey halves, of the Gepe AN mount. It displayed no newton rings hence the reason I asked about plain glass mounts. Apparently you aren't getting the same results with plain glass mounts so maybe my mount wasn't holding the film tight enough against the plain glass to cause newton rings.

I assume you mean to say that you do not want to see Newton's Rings?

or are you talking about the irregular pattern on the AN glass being projected on the screen? In which case, try tweaking the focus so the AN surface is out of focus keeping the emulsion in focus.

Yes I am talking about the AN pattern projected on the screen. I just upgraded the lens from a f3.5 to a 2.8 the smaller DOF of the new lens is not small enough to eliminate the pattern without softening the image.

The previous posters are 100% correct.

Just to be sure everything is ok with the projector or screen, have you tried projecting:
1) no slide (or a non-glass mount without film in it)
2) an empty glass mount
3) a slide in a non-glass mount

If yes, what are the results? do they change after a minute or two? (if yes it can be a hint for condensation as AgX said)

I’m pretty sure you do this correctly but just in case: The order for mounting slides into GEPE mounts is: the black side facing the screen; then the film with emulsion side facing the black side; then the white side of the mount.

Hope this helps

I'll try your steps to eliminate the possibility of it being the projector. Assuming it's condensation in the slide, should heating my slide trays before projection help? I really don't want to be limited to 10-15 seconds of viewing!

I also ordered another batch of Gepe AN glass mounts in hopes I got a bad batch of mounts. I cant imagine so many being so happy with seeing this pattern in their slide shows. I even emailed Gepe about it and they said no one else has complained. I cant imagine I'm the only anal user demanding optimum image quality with NO degradation from AN slide mounts.

 

[1kgcoffee]

Besides the newton rings, is the image quality that underwhelming? I am looking forward at finally starting MF projection and have been told there is a wow element that can't be explained.

 

[AgX]

Sounds like a real possibility however I'm not getting the process. If the slide goes in cool the first thing to heat is the glass then the transparency. What cooled panes are you refereeing too?

-) How can the glass be heated first?
Common glass is quite transparent to IR radiation. The dyes in the emulsion however partially absorb the visible light and heat up by this.

-) with "cooled panes" I referred to the AN-glass panes of the mount. Some projectors, though maybe not yours, have an extra channel to blow air of room temperature along the slide mount.

 

[sruddy]

Besides the newton rings, is the image quality that underwhelming? I am looking forward at finally starting MF projection and have been told there is a wow element that can't be explained.

I have ever seen an image this big with so much resolution. If, and this is important, you have a great taking lens, and a great projecting lens, you WILL be blown away by the detail and immersion. For me seeing the pattern caused by using anti newton glass mounts ruins the experience. All my eye wants to do is go to the part of the image were the pattern is visible. I will continue to experiment and will post my results here. I will also post a few screen shots to illustrate my issues.

 

[sruddy]

-) How can the glass be heated first?
Common glass is quite transparent to IR radiation. The dyes in the emulsion however partially absorb the visible light and heat up by this.

-) with "cooled panes" I referred to the AN-glass panes of the mount. Some projectors, though maybe not yours, have an extra channel to blow air of room temperature along the slide mount.

Ha ha, I have now idea that's why I asked! I assumed since the glass was closest to the heat source it would get hot first. It sure felt hot to me after I ejected it. According to your explanation the hot AN glass panel is cooler than the hot transparency. Anyway I got it now. I just have to figure out how the get the moisture out of my slides before viewing them and or modify my projector to keep the slides cool.

 

[Alan Edward Klein]

One suggestion. Tell your guests that dessert will be served after the slide show. You don't want them to complain about some made-up ailment so they go home beforehand.

 

[AgX]

Ha ha, I have now idea that's why I asked! I assumed since the glass was closest to the heat source it would get hot first.

With any heat source one must differenciate between

-) conduction (eg. a lamp socket)
-) convection (an air stream)
-) radiation (typically IR)


All better projectors have a thick IR filter so this radiation is cut off for the most already.

 

[jtk]

Two realities: #1 projection destroys slides (heat). If you have real archival concerns you should project duplicates. #2you may be seeing an alcohol oil that results from bad processing.

 

[itsdoable]

...
Yes I am talking about the AN pattern projected on the screen. I just upgraded the lens from a f3.5 to a 2.8 the smaller DOF of the new lens is not small enough to eliminate the pattern without softening the image...

I used a Rollei P11 with a Heidosmat 150/2.8, and the Gepe AN glass mount slide. And now that you mentioned it, I think the AN pattern was faintly visible, but it depended a lot on the screen/projection surface. I don't recall the pattern recall being distracting, but it could have been my setup was not sufficient to show this.

...I cant imagine I'm the only anal user demanding optimum image quality with NO degradation from AN slide mounts.

I'm sure you are not the only one. If you do not get Newton Rings with plain glass mounts, then that is what you should use. Some polyester film bases have a wrinkle pattern to them, which resists Newton's rings. Kodachrome always gave me Newton's rings if I did not use AN glass, but it also projected OK without glass. You can also try regular glassless mounts, but you should use a lens designed for that with a curved focal plane.

 

[AgX]

You can also try regular glassless mounts, but you should use a lens designed for that with a curved focal plane.

There are mounts that fix the film under lateral tension thus keeping it from bulging. One thus has to experiment which type of lens design is best.

 

[jtk]

There is no "AN pattern". AN glass is chemically eroded to produce a finely textured surface with no pattern at all.

 

[Ferdi]

You mentioned the projector being 'restored' with a new lamp. Is that a more powerful (more W) lamp than original? That would mean more heat in the projector. In my P11 an extra heat filter has to be placed when using a 500 W lamp instead of 300 W IIRC. The combination of moist slides and a powerful lamp means trouble. You could try 'pre-warming' the slides before projection. A photographer I know put the boxes with slides on to the central heating radiator or in to the sun. He used a huge Götschmann projector wit a massive amount of light (and heat) for slide shows in cinemas.

 

[sruddy]

One suggestion. Tell your guests that dessert will be served after the slide show. You don't want them to complain about some made-up ailment so they go home beforehand.

Ha Ha yeah I know, those photo club members can be brutal! My mother in law would definitely stay for desert.

With any heat source one must differenciate between

-) conduction (eg. a lamp socket)
-) convection (an air stream)
-) radiation (typically IR)


All better projectors have a thick IR filter so this radiation is cut off for the most already.

Mine has a 1/8" glass filter. I experimented yesterday. The room temp was 72. Here is a list of temps using different lamp intensity settings.

• outside temp 72 degrees
• #2 - 73
• #4 - 74
• #6 - 75
• #8 - 79
• #10 - 87

Two realities: #1 projection destroys slides (heat). If you have real archival concerns you should project duplicates. #2you may be seeing an alcohol oil that results from bad processing.

I cleaned the slide that was having this issue with 99% alcohol. Still had the problem but not as bad. For some reason this negative is wavy and I see the distortion form right along the area were the neg curls into the anti newton panel. The Gepe mounts have lots of air space. They do not flatten a wavy or curled neg.

I used a Rollei P11 with a Heidosmat 150/2.8, and the Gepe AN glass mount slide. And now that you mentioned it, I think the AN pattern was faintly visible, but it depended a lot on the screen/projection surface. I don't recall the pattern recall being distracting, but it could have been my setup was not sufficient to show this.


I'm sure you are not the only one. If you do not get Newton Rings with plain glass mounts, then that is what you should use. Some polyester film bases have a wrinkle pattern to them, which resists Newton's rings. Kodachrome always gave me Newton's rings if I did not use AN glass, but it also projected OK without glass. You can also try regular glassless mounts, but you should use a lens designed for that with a curved focal plane.

Looking for plain glass mounts to try. I haven't found any yet. I cannibalized one of the AN mounts to make a glass-less one and it showed no Newton Rings, If it turns out my film isn't susceptible to forming newton rings I'll be in heaven.

There are mounts that fix the film under lateral tension thus keeping it from bulging. One thus has to experiment which type of lens design is best.

Have a name? I'm only finding the Gepe AN mounts and Matin glassless.

There is no "AN pattern". AN glass is chemically eroded to produce a finely textured surface with no pattern at all.

Ok thx, irregular pattern then.

You mentioned the projector being 'restored' with a new lamp. Is that a more powerful (more W) lamp than original? That would mean more heat in the projector. In my P11 an extra heat filter has to be placed when using a 500 W lamp instead of 300 W IIRC. The combination of moist slides and a powerful lamp means trouble. You could try 'pre-warming' the slides before projection. A photographer I know put the boxes with slides on to the central heating radiator or in to the sun. He used a huge Götschmann projector wit a massive amount of light (and heat) for slide shows in cinemas.

I am using the lamp specified and just took temp readings listed above. I was setting my lamp at nearly 10 but now I'm going to try 7.5 or 8 which will save me nearly 10 degrees and will only be 5 degrees over ambient room temp.

Things for me to still try:

1. Run lamp at a lower cooler setting
2. Try to find plain glass mounts and hope I don't get newton rings
3. Look into proper way to mount slides in gepe an glass mounts giving flattest results. (maybe I'm doing it wrong)

 

[AgX]

Concerning your question on slide mounts:
Ther are currently slide mounts that fix the filmstrip in deliberat lateral position as well keep them under deliberate tension. However only made for 35mm film...
(https://www.photrio.com/forum/threads/new-35mm-slide-mount-system.97343/#post-1291749)

 

[sruddy]

Concerning your question on slide mounts:
Ther are currently slide mounts that fix the filmstrip in deliberat lateral position as well keep them under deliberate tension. However only made for 35mm film...
(https://www.photrio.com/forum/threads/new-35mm-slide-mount-system.97343/#post-1291749)

Thank you.

FWIW I forgot to mention I took a temperature reading with the cover off. At 9.5 output, I got 115 degrees. I could be wrong but I believe this is hot enough to cause the negatives to develop a curl. I also believe this curl is responsible for the image degradation I first mentioned, as the degradation happens were the curl touches the AN glass. When I first got the projector it was a doorstop. During my restoration I used it without the cover several times. I believe this is when I ruined some of the transparencies. So I think I have my second issue solved. Don't operate the projector with the cover off! Duh....

 

[outwest]

If you are worried about quality try a Hasselblad PCP 80.

 

[sruddy]

If you are worried about quality try a Hasselblad PCP 80.

I chose to go with the Rollei projector because I have Rolleiflex cameras and it iwas much more affordable than the PCP 80. If a PCP 80 ever fell in my lap I sure would give it a try though! IMO, using the same slide mount and high end projecting lens there should be no visible image difference from the two projectors. I do want to upgrade to the most recent Rollei 66 Dual P for a quieter experience and a working AF system. Right now I'm trying to repair the AF on my P66S.

I have given up on Gepe AN Glass mounts. Depending on the flatness of the transparency they can be be hit or miss. The thing is that the mount has a gap of .022" between the glass. The transparency is only .005" thick so that leaves you with 017" left over. This is actually needed as if the transparency was completely against the AN panel the AN texture would be very visible. I think they developed them to keep the transparencies contained but not perfectly flat against the AN pane. The DOF of my lens is such that if I focus on the AN texture the neg should be out of focus and visa versa. So if the neg has a bulge that is touching the AN panel in an area like a flat sky then your going to see the AN texture. This is why I say hit or miss. It depends on the image and which part of it if any is touching the AN pane.

I tried Matin ABS Plastic Slide Mounts, ha ha, don't waist your money! They are very cheap with plastic imperfections and after assembly they do not lay flat at all. Next try was Gepe Glassless with metal mount. I think they have been have been discontinued. :-( These seem to be my answer but may take awhile to find more. I have 80 mounts to get me started. This is a test slide using the low quality Matin glassless mount. You can see the bottom right x is soft focus were the mount was not flat. This won't be an issue with the Gepe Glassless.