Gast
Hello,
Can anyone help me with the following problem:
When I look very closely at my black-and-white enlargements (mostly in 24x30 cm format), I notice that there are areas that are out of focus along the right-hand edge, particularly in the top-right corner; in some cases, the grain that is clearly visible in the centre of the image is barely discernible at the edge. The problem rarely occurs at the left-hand edge of the image. The out-of-focus areas also occur when I make a cropped enlargement of parts of the image that are more towards the centre.
I enlarge 35mm negatives using an Axomat 5 with a Rodagon 2.8/50 lens.
Is this a phenomenon that one simply has to accept with a glassless negative stage, such as the one on the Axomat? Are there any other possible causes for the out-of-focus images apart from the negative not lying perfectly flat? What might help?
Many thanks in advance for your advice
Christian
Gast
Christian,
It’s highly likely that the problem lies with the alignment of your enlarger. Unfortunately, fixing it is far from straightforward. The method described by T. Wollstein using spirit levels (www.sw-magazin.de) is, for various reasons, suitable at best for rough adjustment or not at all (depending on whether your machine has suitable edges against which to place the spirit level).
The second-best method is the so-called mirror method, as has often been described at www.phototec.de.
By far the best adjustment method works with the device from Versalab, which is unfortunately only available in the USA. You can also read more about this at phototec.
So I won’t go into further detail here.
Best regards
Ferdinand
MKL
I’d also say it’s down to the alignment. The easiest way to align the enlarger is to use a test negative. I have one from Hama that shows a circle with microstructures in each corner. That works quite well.
Best regards,
Michael
Gast
Michael,
I can’t agree with you on that. Whilst a test negative can show whether the problem lies with the alignment, it doesn’t reveal where the fault lies. As you know, three planes must be absolutely parallel (base plate, lens, negative). A test negative just marks the start of endless trial and error.
Best regards,
Ferdinand
Gast
Hello,
What aperture do you use for exposure?
I get the best sharpness with my Rodagon at f/5.6. I once read online (on Google) that someone only achieved full sharpness at f/8.
Could it be that there are differences in quality between Rodagon lenses?
Regards, Sven
MirkoBoeddecker
Christian,
Have a go at this:
1) Does your Axomat have a Scheimpflug correction function at the bottom of the lens mount?
If so, is it set to the zero position?
If not: there should be a nut there to secure the whole thing – is it still tight?
2) Is your lens perhaps screwed into the board’s thread at an angle?
3) Is the circuit board firmly and correctly seated at all three contact points?
4) What aperture are you stopping down to?
5) Is one of the two springs at the top, which press the image stage downwards, possibly missing, or is one too weak?
6) Is your stage parallel or bent?
General: with a glassless stage, objects can theoretically become out of focus from the centre towards the edges, but in that case they should become out of focus from the centre towards all edges, not just one.
Otherwise, it’s more likely to indicate misalignment or a lens problem.
Regards,
Mirko
Gast
Many thanks for your suggestions! I’ve learnt a lot in the process (e.g. that you should readjust your enlarger from time to time), and Mirko’s checklist has encouraged me to take a closer look at some of the finer details of the enlarger – I hadn’t really paid much attention to all those screws before … I can’t actually check the results of my fiddling around at the moment, as my Duka isn’t set up at the moment, but since the Scheimpflug (which I never use) wasn’t quite set to ‘0’ as I discovered, I assume that was the reason. The Rodagon is pretty much OK, I think. I usually work with an aperture of f/5.6.
Ferdinand, the tip about the mirror method was very useful for me; I’ll definitely give it a go.
So far, I’ve only posted questions on this forum, not answers. I hope that’s OK with you all. As I don’t have much experience with the Duka yet, I don’t have much to share either.
Best regards from Graz, Austria
Christian
Gast
Christian,
Unfortunately, the zero stops on various enlargers do not guarantee perfect alignment. On the contrary, they often get in the way when you need to make very slight adjustments. I’ve removed them from my unit (Dunco).
Best regards,
Ferdinand
MKL
Hi Ferdinand,
I’ve got the Dunco too, and the connections do get on my nerves sometimes as well. What exactly did you remove it from, and how big are your mirrors for the adjustment? 10x15 cm seems a bit large to me. The lens board wobbles a little when I change the focus adjustment direction. Is there a trick to it?
Best regards,
Michael
Gast
Hi Michael,
If I remember correctly, the pins that click into place at the zero stop are threaded, so you can simply unscrew them.
I couldn’t get to grips with the mirror method on my Dunco (which is why I wrote ‘second-best method’), for the simple reason that I can’t see how to position the upper mirror (the one with the hole) at the objective plane. Of course, you can create reference planes by placing a steel ruler against it, etc., but in my humble opinion it remains an unreliable business.
That’s why I temporarily switched off my rational thinking and had the Versalab shipped over from the US (my excuse was the favourable dollar exchange rate) – not a cheap affair, as UPS charges and import VAT all add up.
Perhaps Mirco can sort something out via his US trading partner. The device is really brilliant.
Regards
Ferdinand
skahde
"second-best method"), for the simple reason that I can’t see how to position the upper mirror (the one with the hole) at the lens plane. You can
Hello,
you can try (!) to see if the filter thread of the lens is positioned precisely enough perpendicular to the optical axis of the lens and attach the mirror there. It worked for my EL-Nikkor back then, and the alignment achieved in this way produced sharp grain in all corners. The Versalab clearly has the advantage here, but it’s worth a try – and certainly worth quite a bit in terms of $$$. ;-)
Best regards,
Stefan
Gast
Stefan,
When aligning the lens plane using Versalab, the filter thread also has to be used to secure the glass plate (which reflects the laser beam). My problem was more about carrying out the actual adjustment whilst holding the mirror in place; you need about three attempts to get it right. Of course, you could also just look through it – adjust it – look through it again – adjust it again, and so on. Considering the price of the Versalab, that’s actually not a bad hourly wage. I’m just a bit of a lazybones.
Best regards
Ferdinand
