I bought a 2nd hand 150/f5.6 Componon-S for 5x4 enlargements a couple of years ago.
I have always focused the lens wide open then stopped down a couple of stops (normally 2 stops to f11)
However, last night I checked the focus again when I stopped down to f11 and found the focus which had been fine at f5.6 was very slightly out.
I then did a couple more checks and found that the focus at f11 was indeed different from the focus at f5.6 – and consistently so.
I can rule out inadvertent movement to the lese stage during stopping down – as it would return to correct focus when the lens was set to its focusing aperture
I don’t know how old the lens is or its history but externally it looks fine and has not scuff marks or dents to show any damage
Has anyone else experience of focus shift on Componons?
Strange, I've been using Componon's and Componon S's for quite a few years in various focal lengths and have never had a focus shift.
Someone on this forum had a very similar problem 6 months or a year ago, it turned out to be the enlarger head was creeping very slowly down the column. It was Durst enlarger in that case, they have a friction adjuster that wears over the years, you just need to tighten them every so often. I have had this happen myself but it showed up far more apparently.
Hi Ian, I thought at first I must have been a bit ham fisted and moved the lens carrier as I adjusted the aperture but when I focused at F5.6 and checked it at f11 it was out and when it was set back to 5.6 it was right again.
I then did it at f11 > 5.6 (out) > f11 – good again
I also noticed I had to adjust be the same amount (obviously in opposite directions) between f5.6 & f11
Therefore I am pretty sure I hadn’t moved the lens
I checked my other lenses (bought from new and carefully looked after) and no focus shift
I had considered focus shift of enlarger lenses as a historic phenomena – that modern good quality lenses didn’t (shouldn’t) do
Martin
Sponsored Ad. (Subscribers to APUG
have the option to remove this ad.)
Martin, I read this after dinner, before going to develop some film.
After the film was developed I put a 4x5 neg in and using my 150 f5.6 Componon S I checked out your situation on my own enlarger.
Firstly I checked it using my Peak grain focus finder, which is about the best in the business, then I did the same thing with my Paterson (small) grain focus finder.
There was a noticeable difference between the two, but this is mainly the ability to see slightly more stopped down with the Peak, than the Paterson.
What I found after careful evaluation was that using FP4+ film, set to enlarge onto a 12x16 sheet of paper, I was able to see grain wide open. I then stopped down in ˝ stops, with my eye constantly at the eyepiece. I noted that after 1 stop it looked ever so slightly that the focus had shifted, at 2 stops a poofteenth more looking out of focus, 1 more stop to f16 and my eyes just cannot see well enough to figure out what I'm seeing. This was more or less the same for the Paterson, except f11 was it on that unit.
The thing though, whilst at first it looked as though it was going out of focus, it wasn't, could your problem be the message your eye is sending to your brain, it certainly at first seemed like that to me.
Then a few times I clicked the lens open, yes it was in focus, that is, I could see the grain. I did this with both grain focusing units, they both did the same thing.
I then focused at f11, which is the darkest I can see grain at, I then opened the lens in ˝ stops and watched the previous thing happen, but in reverse.
There is of course a bit of a thing happening with our eyes, they really don't see too well as the light level drops, you do have good eyesight I assume? A 150 lens is usually a reasonable amount harder to focus carefully as the enlargement is usually smaller, therefore the grain is harder to see. The light on the enlarger has to work at it's maximum spread, usually making it ˝ a stop darker before you start.
As you have had the lens for some time, am I right in assuming you weren't happy with what you were producing with it?
Are you saying the prints are out of focus,
or are you judging the image in the magnifier ?
If you focus the image with the Peak,
and the prints are out of focus,
then all you have to do is confirm that you've adjusted the eyepeice properly
(look at the directions packed with the Peak). This IS important.
'Focus Shift' is a design flaw, not some sort of entropy
like a toaster evolving into a lawn mower.
When you stop down, you're have four problems;
depth of field, a 3 dimensional subject, and diffraction.
Diffraction reduces the resolution of the lens (as magnified by the Peak).
AS you stop down, you are now looking at an image with depth,
as the increased depth of field makes it harder to discern the exact plane of focus.
Finally, the image is darker, harder to see.
If the pictures focussed at f/5.6 are not good, and the Peak's reticle is adjusted,
then the lens might be suspect. But there isn't much that ever goes wrong with an enlarging lens.
Schneider Componon-S 150/f5.6 Focus Shift 
Linear Mode
