Below the lens filters and sharpness?

[mealers]

I've just finished refitting my darkroom, apart from really thinking about the best possible layout the major reason for this overhaul was to fix my enlarger to a solid wall to minimize any vibrations.
Everything has gone good, I've used a laser level to align my enlarger and after a bit of messing about I'm fairly confident everything is spot on.


Now for the reason of my post -
I have been doing alot of split grade printing recently and one thing I have noticed is how easy it is to lose focus as soon as I touch the colour dials to change grades.
So I'm now thinking about using Ilford below the lens filters but is there really a visual lack of quality in the prints when using them? I guess the biggest prints I will do is 20x16.

If I choose to go this route I'm also going to have to change my Rodagon to something with a smaller lens diameter for the filter collar to fit. More expense but if its worth it and the print quality doesnt suffer too much I'm quite willing to pay!

Mike

 

[David A. Goldfarb]

Ctein made some careful tests and determined that even CP filters designed to go above the neg didn't degrade sharpness under the enlarging lens.

That said, you shouldn't be losing focus when you touch the dials. Is everything else working properly?

 

[mealers]

That said, you shouldn't be losing focus when you touch the dials. Is everything else working properly?

Yep everything works fine, it only loses focus ever so slightly. When I've completed the print and when I check it again with a focus finder the grain isnt quite as sharp as when I started, maybe I'm just being a little heavy handed?

 

[Ian Grant]

You may need to adjust/fine tune your enlarger if the focus creeps, it's most likely the head creeping up/down the column (not the actually focus part). On many enlargers there are pressure pads, these wear and need adjusting occasionally, it's very quick & simple to do..

Over the years I've used below the lens holders & the filter drawer for MG filters with excellent results, I now use the Colour heads on my Durst & De Vere again with no problem with Split Grade printing.

Ian

 

[Andrew Moxom]

Could it be your lens stage moving ever so slightly during exposure? Or could the neg be moving slightly under the heat? There really should not be any focus shift from you changing these dials. Something is amiss if so. What enlarger and lightsource do you have?

 

[Ian Grant]

There was a thread a year or two ago about a very similar problem with a Durst, they are prone to creep if touched. I saw it happen with my first Durst, it had a hard life in a commercial darkroom, then one day I noticed it sliding up the column. The Focus stages never usually shift. Most enlargers have some kind of spring or counter weight, these are actually quite strong so there are friction pad to dampen & stop the head creeping.

Ian

 

[Chuck_P]

So I'm now thinking about using Ilford below the lens filters but is there really a visual lack of quality in the prints when using them? I guess the biggest prints I will do is 20x16.

If you do use a below the lens filter system, the filter should be as close to the lens as possible

 

[erikg]

I've used filters under the lens for years and it works great, I could never see any differences in my tests and that Ctein article put my mind at rest. I do check the focus as I go, the neg will move a bit from heat, I try to not let it cool down once I get into the final prints. You do need to have a light touch changing the filters but it's not too hard.

 

[mealers]

Thanks for the replies everyone.
I'm still waiting for a chance to get back in the darkroom and print as I'm snowed under with work!

I've got a feeling that it may be the enlarger head creeping down when I touch the filters.
I've pretty much decided I'm going to buy some under the lens filters though, that and get another lens, if only they made bigger filters and a collar to fit 150mm Rodenstock!

 

[Ian Grant]

The 135mm Componon & Rodagon are great for 5x4, you don't need a 150mm, unless of course yot enlarging 5x7. Coverage & sharpness is superb.

Ian

 

[mealers]

The 135mm Componon & Rodagon are great for 5x4, you don't need a 150mm, unless of course yot enlarging 5x7. Coverage & sharpness is superb.

Ian

Do you know what size thread they have on the lens?

Mike

 

[Ian Grant]

Both mine are in the UK, I'm in Turkey keeping warm It's on the Schneider websites, actually I think I gave my best 135mm away with a 5x4 enlarger for free 2 years ago

But they do cover 5x4 easily, I use a 240mm Rodagon for my 5x4 negs.

Ian

 

[Martin Aislabie]

Thanks for the replies everyone.
I'm still waiting for a chance to get back in the darkroom and print as I'm snowed under with work!

I've got a feeling that it may be the enlarger head creeping down when I touch the filters.
I've pretty much decided I'm going to buy some under the lens filters though, that and get another lens, if only they made bigger filters and a collar to fit 150mm Rodenstock!

Mike, I have an Ilford Under the Lens Filter Holder - on a 150mm Rodagon-G

I also have a Schneider Componon-S (52mm filter) and it fits too

However, my Filter Holder may be of an earier design.

Martin

 

[ic-racer]

if only they made bigger filters and a collar to fit 150mm Rodenstock!

Here is a link to a thread where I made a holder for the 6" filters to fit a 300mm Rodenstock. http://www.largeformatphotography.info/forum/showthread.php?p=390777#post390777

 

[mealers]

Thats funny, I just found your old thread and was about to PM you for more info, no need now.
Thanks very much

 

[nworth]

The usual below the lens filters are too thin to cause a focus shift, but the image could certainly be degraded if they are dirty.