Meopta Opemus 5 filter drawer diffuser.. function?

Monokrom · Apr 9, 2020

Hi! Just bought a new in box Meopta Opemus 5 purchased by the seller in DDR early 80s but never assembled and used. I set it up and have been doing some test prints, studied the manual (PDF online English version) but there's one thing I can't figure out.

In the bottom of the filter drawer is a coarse matte glass, should this always be used and filters stacked on top of it if needed? What is the function of this glass? Any Opemus owners out there who knows?

/Petter

pentaxuser · Apr 9, 2020

I take it that you cannot focus the neg with this in place. If so it suggests to me that it was used to diffuse any neg into a uniform grey for the purposes of setting an exposure for the print that was designed to work well for negs that were an 18% grey when the tones were mixed

Just speculation on my part but it looks too textured to have any other use such as soft focus

pentaxuser

Monokrom · Apr 9, 2020

It's placed just under the light source so not in the path of the projection, but I might have found the answer in the manual after reading it thoroughly again. It's apparently for diffusing the light if you want softer grain or if your negative has gradations you want to blur a bit.

pentaxuser · Apr 9, 2020

Thanks I have no experience of your enlarger so didn't realise that this diffuser was not under the path of projection. However when you said it was at the bottom of the filter drawer I thought that as the filters for multigrade papers have to be under the path of projection to work, it had to mean that this diffuser was also under the light path which shines through the filter and then through the negative

I am still confused as to how it diffuses without being in the light path in the sense of at least interfering with the light to change it. If there a diagram in the manual that shows how it works?

Thanks

pentaxuser

Monokrom · Apr 9, 2020

Sorry I was not very precise, It is in the light path before the negative carrier, just below the lamp and before the condenser.

pentaxuser · Apr 9, 2020

Monokrom said:
Sorry I was not very precise, It is in the light path before the negative carrier, just below the lamp and before the condenser.

OK and thanks I now understand. You are right about there not being very much about it on the internet I couldn't find any mention of it in my searches

pentaxuser

Jojje · Apr 10, 2020

Heat shield? I have this in my Opemus 6. Never taken it away.

Monokrom · Apr 10, 2020

@Jojje , It's apparently for softening up grain, gonna remove it next time i print and see if I notice any difference in sharpness .

MattKing · Apr 10, 2020

Monokrom said:
@Jojje , It's apparently for softening up grain, gonna remove it next time i print and see if I notice any difference in sharpness .

More accurately, a diffused light source will reduce contrast, including in particular the edge contrast - also known as acutance.
Acutance is the major component of what we subjectively observe as "sharpness".
By changing acutance, diffusion will change the appearance of fine details, including the appearance of grain.
Diffusion will also tend to suppress the appearance of dust and any markings on the film.

hadeer · Apr 10, 2020

[QUOTE="MattKing, post: 2268429, member: 6437"[QUOTE a diffused light source will reduce contrast, including in particular QUOTE]
Right. The Opemus is a condensor enlarger. With the diffusion glass in place it mimics being a diffuser enlarger, so reducing overall contrast. It's a clever trick from Opemus to help you print negatives witk a tick too much contrast

Monokrom · Apr 10, 2020

Thank you @MattKing and @hadeer for the more in depth explanations, will be interesting to see how much difference it makes using the same originals.

pentaxuser · Apr 10, 2020

Monokrom said:
Thank you @MattKing and @hadeer for the more in depth explanations, will be interesting to see how much difference it makes using the same originals.

I am certainly interested in how much difference the filter makes Some people say that all things being equal it is at least half a grade so if grade 2 is right in a condenser then it needs at least grade 2.5 in a diffuser enlarger

pentaxuser

hadeer · Apr 11, 2020

A half to less then one grade corresponds to my experience. I never measured it though and I switched to the Kaiser 6000 system V later on

pentaxuser · Apr 11, 2020

One day I must print the same projection for say all the grades including half grades, write on the back of each its grade as I print then without looking see if I can rank them in the right order. I once looked at such a range of prints in a darkroom book and frankly could not really distinguish half grades.

Maybe I wasn't looking on the right area of the prints

pentaxuser

hadeer · Apr 12, 2020

True. To see the difference I suppose printing a stepwedge will show it.

MattKing · Apr 12, 2020

The diffusion will affect the contrast, but it will have other, more subtle effects as well.
In addition to comparing contrast, it is important to compare how fine details are rendered.
By the way, when we talk about contrast, we don't mean the range of tones - dark to light. We mean the transitions between similar tones.

Meopta Opemus 5 filter drawer diffuser.. function?

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