PeterTV
Hello,
I bought a "new" FEM MP104 multitimer on eBay. The device comes from a business liquidation and is supposedly new.
I determined the ISO speed for my paper (old TT Variospeed – Agfa MCP) using the test negative and grey scale chart provided.
Full of enthusiasm, I then proceeded to enlarge the image and measured two very dark areas with shadow detail and two bright areas with shadow detail. The average of the measurement was 33 s.
However, on the subsequent test strip for fine-tuning the exposure, none of the values were correct – 33.1 s – 1/3, +1/3, +2/3 stop above the timer.
It was only at 57 s that the desired density was achieved.
My question now is: is there a correlation between the age of the light meter and its speed, i.e. should the light meter’s speed increase with age and decreasing light levels?
What influence does the age of the paper have – TT Variospeed has not been available for some time now. It is neither slow nor soft. Could it be that the paper exhibits a stronger Schwarzschild effect before it becomes unusable?
I use Agfa Neutol WA as the developer. The bottle has been open for about a year, but is stored in a cool, dark place. Can the developer have a significant influence on the speed of the paper?
Here is some further information on the development process.
Paper in Jobo CPA 2 drum at 20°C, 160ml each
90s development with Neutol WA 1+15, 20ml loss each time so that after 8 sheets (24x30cm²) the developer was completely replaced
30s citric acid-based stop bath
30s fixer I (fast fixer 1+4)
30s Fixer II (fast fixer 1+4)
Rinsing with four water changes after 30, 60, 120 and 240s.
The process is strictly adhered to and carried out using a process timer.
I am grateful for your comments.
Wolf_XL
...two things – from my own experience – spring to mind:
- You should limit yourself to the lightest and darkest areas on the negative – that’s quite sufficient. Because I doubt you’ll be able to find the second-lightest area as well as the second-darkest... In my experience, multi-point metering is pointless – the more points I measured, the less accurate the result became...
- I also consider calibrating the device using a test negative to be suboptimal – because in practice, a negative very rarely offers the full range of contrast. I would use an average negative for calibration.
However, as far as I know, the FEM has a button that allows you to correct your paper index. This should work as follows:
1. Measure the brightest and darkest areas
2. Expose the paper, develop it – then optimise the exposure time until the positive is as desired.
3. Repeat the measurement, enter the optimal time manually and press the index button. The index number will now be recalculated and displayed. Note this index on the paper box.
hansschneider
Dear Peter,
I own two Kunze MP 109s, which, as far as I know, differ from your unit only in minor details, but also – and above all – in that with the 109, the darkroom light can be left on, whereas with the 104, if I’m not mistaken, it cannot.
This brings us to the first possible error: did you carry out all the measurements with the darkroom light switched off?
The second point: calibrating to the paper speed using a test negative: contrary to the opinions of third parties here, which are clearly based on pure conjecture and are therefore of little help, this works very well.
In my opinion, if an error occurs during measurement, it is unlikely to lie in the calibration using a test negative, but rather in the subsequent use of the negatives to be enlarged. You write that you took readings from two very dark areas and then from two bright areas. In my experience, this is the most likely source of error; a light meter is no substitute for experience. You need to find such dark areas where you can still make out detail – and do the same for the light areas, i.e. the shadows – and this can only be achieved through practice. Furthermore, no one here knows whether your negatives are affected by underexposure; based on your description, that could well be the case (hence the long exposure times).
If you are sure you have a normally exposed negative, then meter two ‘medium-dark’ areas, then two ‘medium-light’ areas.
Another possible error could lie in the operation. Do you know how to apply the readings you’ve found – taken at full aperture or stopped down one stop – to the working aperture?
This may be made more difficult by the fact that, although the Kunze instruction manuals are detailed, they are obviously written by technicians and engineers – and they really ought to be forbidden from doing so. To avoid having to work my way through the four different booklets and sheets of paper again after long breaks, I have written my own instruction manual, and wonderfully enough, it only takes up two pages.
Finally, there is the question of developer and paper. The developer you are using (if I recall correctly) goes off after six weeks in the opened original bottle, according to Agfa. Are you using the same paper/developer combination for both calibration and enlargement?
In summary, I suspect that your problem lies not with the equipment, but with the calibration process. In any case, that’s what you’re hoping for; process errors can be rectified, but equipment faults are expensive.
If needed, I’d be happy to help you with the individual measurement steps, as far as I can here. If it’s any consolation: at the start, I cursed the equipment too, but the errors were, as is almost always the case, down to the settings. Overall, the Kunze machines are brilliant, as they always let you retain control over the individual steps.
Conclusion: If, after adjusting the individual paper/developer sensitivity on the device, you manage to produce a good print from the test negative on the second or third attempt, it is quite likely down to your subsequent steps.
Best regards
Hans
cfb_de
Hi Hans,
I completely agree with you. Would you perhaps be able to share your two-page document here?
Actually, the Kunze-104 and my Trialux don’t seem to differ much. Measurements in the *dark* chamber. Incidentally, this can be got round using a suitably wired cross-over switch. As long as no electrician realises that 12/24V and 235V mains voltage are on the same switch.
The correct approach, of course, would be to fit a relay box in between and have the safety extra-low voltage come in somewhere further down the line...
Best regards,
Franz
Urnes
Yes, Hans, I have to agree with Franz – I’d also be interested in the double-sided version. As I don’t get into the lab very often, I’ll have to struggle through those rather dry instructions all over again.
Otherwise, I have to say that I’m more than happy with my 104. If something isn’t quite right, it’s usually because I’ve either measured the wrong point or my vision of the image is simply different, but then I have a good basis for adjusting the parameters.
Regards, Sven.
hansschneider
Could you perhaps share your two-page document here?
Dear Franz,
I’d be happy to, but I’ll give the text a critical read-through first, as I wrote it for myself and it may therefore contain things that seem obvious to me.
Please bear with me.
Best regards
Hans
cfb_de
Hello Hans,
Many thanks in advance!
Best regards,
Franz
AndyBauer
Hello,
And what has become of it since then?
I’d be very interested to know.
Best regards, Andy
Hello Hans,
Many thanks in advance!
Best regards,
Franz
Wolf_XL
...he’s probably still messing about with false negatives, or he’s given up on the whole thing long ago because he listened to that smug windbag Hans Schneider instead of the engineer Wolf_XL... ;-)
Wolkenkratzer
Hello
I have a Trialux and initially had a similar problem. The root cause was incorrect calibration. It was only after a tip from a very experienced photographer that I started getting the right results. Now I’m able to achieve good results straight away when taking standard shots with the Trialux.
I also use a test negative, a grey scale with various grey levels ranging from a density of 0 to 1.65. I calibrated the paper against this and determined the paper index for each paper grade. There must be no fluctuations in lighting between making the test print and measuring the paper index. Stray light, DUKA light, reflections from light-coloured clothing, etc. Fluctuations on the enlarger caused by who knows what had resulted in different paper indices for me.
I have created a paper index for each grey scale. My procedure is to first measure a representative density point by taking a density reading on the negative. I then determine the paper gradation. I then enter the paper index for this paper gradation and for this grey-scale density value. I measure the exposure time at the representative point. In other words, a single-point measurement.
I rarely achieved good results straight away by taking the average between the lightest and darkest points. I usually only use averaging when the grey values fluctuate around the reference value of the grey scale. A reference shot of a homogeneous surface as the first frame on the film also provides an initial guide for the exposure time. I know that my light meter tends to expose for mid-grey. I assign this to a reference density of 0.75. This is usually sufficient for quickly printing a series on postcards.
The densities of the grey scale should be above the fog density of the negative. To achieve this, I stuck an unexposed section of a negative onto the grey scale using Tesa tape. My fog densities are typically between 0.25 and 0.35. I was also amazed by the quality of the enlarger’s illumination. The working aperture, with a maximum deviation of 0.08 between the edge and the centre, is 2.8/50mm f5.6 on my Schneider. At f2.8, the deviation is as much as 0.25. A factor that causes headaches during calibration.
The distance should also be within the range of the usual enlargement factor used. The effects of stray light can be quite frustrating. I have different paper indices for postcards and 25x30 prints.
The calibration process runs from the paper, through the enlarger (including all sources of interference), to the measuring device. All sources of interference must be minimised here.
The paper index defines the paper’s sensitivity for a specific grey tone on the paper. A bit of zone theory does help one to understand the relationships correctly.
After the third attempt, I’d got it.
