Durst L1200 DIF1 and DIF2 diffusers

[RobC]

I have been using a DIF1 diffuser in my L1200 since I've had it. I also have a DIF2 which I've never used. The DIF1 is only half the thickness of the DIF2 so I have always assumed it gave less diffusion and therefore sharper projection than the DIF2.
However, I just held them both upto the light together, and if anything the DIF2 transmits more light and is fractionally less diffuse than the DIF1 which has a milkier perhaps more dense appearance even though it is only half the thickness of the DIF2.

I'm just wondering what other peoples experience with these two diffusers is?

Just to add for those who are not aware. The 4x5 diffuser which sits directly above the negative on a Femobox 450N.
They are exchangeable. One end of the retainer is sprung and you can pull it back to get the diffusion sheet out.

 

[RobC]

I justed tested both of these diffusers on my densitometer. How accurate the actual densities are is possibly suspect because of the thickness of the diffusers. However these are the figures:

DIF1 = 0.85
DIF2 = 0.89

Thats less than 1/6 th of a stop difference even though the DIF2 is almost twice as thick as the DIF1.

Does anyone know if Durst said the DIF1 or DIF2 was intended for sharper projection. I will have to test this although I have been getting sharp prints using the DIF1.

 

[Dave Miller]

I have both, and never found or understood the reason for the difference. Since they sit between the light source and the negative why do you think that they should effect sharpness of the image.

 

[RobC]

Well I got a reply over on large format forum saying that one of them gives more even illumination. However, just placing them both on a peice of paper side by side, I can see text on the paper more clearly through the DIF2 which is thicker. That suggests to me that the DIF2 is diffusing less and would therefore be sharper. It might even give more even lighting although I have never noticed a problem.
I will test it next time I have a print session.

 

[Dave Miller]

I'm still not sure why less diffusion should give a sharper image. I believe it would give a less evenly exposed print and reduced exposure times, but not sharper. Presumably if I left the diffusion sheet out I would get a very fast but unacceptably unevenly lit print, so diffusion must be increased until an acceptable trade off between printing speed and evenness is reached. However that does not answer your original question so it is indeed time for experimentation.

 

[RobC]

I'm still not sure why less diffusion should give a sharper image.

diffusion is scattering light in many directions. The measurements I took indicate that the light transmittance of both the DIF1 and DIF2 are more or less the same at around 14%. However, placing both on a sheet of paper with some text on it, shows me that the DIF2 gives a clearer view of the text.
That indicates the light is being scattered less but with similar transmission which means the light will be passing through in straighter lines( not as de- collimated as the DIF1). If that is the case, then it should project a sharper image of negative in the same way as a condenser would, although not as much.
At least that is how I view it.
Or putting it another way. Do all diffusion enlargers give the same amount of diffusion and if not then what is the controlling factor. There is collimated light and then there is de-collimated light. The degree of de-collimation is the amount of diffusion. Less diffusion and the closer to collimated. And as we know, collimated light gives sharper image because it projects a narrower penumbra around grain. More diffusion and the larger the penumbra(softer).

But as always, testing should easily verify this one way or another.

 

[ic-racer]

I would think that on a light source range from [POINT SOURCE to CONDENSER to DIFFUSE], that your two diffusers would be pretty close together on the DIFFUSE end of the spectrum and probably not have an effect on sharpness.

Just curious, are they uniform thickness, or does one have some 'hotspot' correction? I know the 4x5 diffuser for my Omega head is thicker in the center.

 

[RobC]

I would think that on a light source range from [POINT SOURCE to CONDENSER to DIFFUSE], that your two diffusers would be pretty close together on the DIFFUSE end of the spectrum and probably not have an effect on sharpness.

Just curious, are they uniform thickness, or does one have some 'hotspot' correction? I know the 4x5 diffuser for my Omega head is thicker in the center.

They are uniform thickness although the DIF2 is a lot thicker than the DIF1.
However, the Femobox 450N also has a diffuser at the top of the box where the light comes in. That is not uniform.

 

[Dave Miller]

Just found an unused Dif 1 in it's packet which says:

"This diffuser may be used in place of the original (bottom) diffuser when requiring shorter exposure times, i.e. a higher light output."

Still leaves the question as to which one is better.

 

[RobC]

Just found an unused Dif 1 in it's packet which says:

"This diffuser may be used in place of the original (bottom) diffuser when requiring shorter exposure times, i.e. a higher light output."

Still leaves the question as to which one is better.

Does it say DIF1 on the packet/literature itself or just on the diffuser?

 

[Dave Miller]

Just on the diffuser.

 

[df cardwell]

And, just for the pure devilry, there has never been ANY evidence that diffusion enlargers are not as 'sharp'
as condenser enlargers. All we are doing, really, is photographing a flat subject that is trans-illuminated.
Contrast may vary, but that isn't really a factor for we accommodate that in our negs.

OK, get out the pitchforks and torches.

 

[RobC]

Just on the diffuser.

so the packaging could be for either a DIF1 or a DIF2 assuming one or other is in the enlarger and one is in the packaging?

 

[RobC]

Time for testing as I don't think anything will be proved buy talking about it.

 

[Dave Miller]

so the packaging could be for either a DIF1 or a DIF2 assuming one or other is in the enlarger and one is in the packaging?

No, this is a new unit in it's original package.

 

[RobC]

No, this is a new unit in it's original package.

Thats curious as they call the replacement DIF1 so the standard one is DIF2 unless there are others. Anyhow it makes no difference. A test is required to verify if there is difference and which one if either is better.

I'll maybe call Terry at Northern Photo on Monday and see if he can shed any further light on it

 

[RobC]

Well I dug the manual and always the old adage RTFM applies.
It says the additional diffuser is for faster printing times but it also says that one of them gives better colour balance. It doesn't say which one.

 

[Dave Miller]

Now you’ve gone and spoilt it, haven’t you. Reading the manual is always a matter of last resort, we hadn’t got to that stage yet.

Anyway thanks for clearing the matter up.