Cannot get b&w contrast with dichro head

[RobC]

using ilfords own Y+M figures for G5 on my enlarger requires using maximum M without any Y. The speed match is on a print density 0.7 but this was for the old MGIV. I don't how well it works with MGIV Classic until I test it.

 

[paul_c5x4]

A durst L1200 with CLS501 head will as has been verified by myself and several other people on this and other forums.

Indeed. I'd refer Jim to this thread: (there was a url link here which no longer exists) and consider post #16

 

[Sirius Glass]

Check the filters and the lamp. I cannot get to 5.0 but I can get to ~4.5.

 

[Ian Grant]

I'd check your safe-light.

When the newer ranges of MG papers came out in the late 70's/early 80's a few people found they couldn't achieve the higher contrasts. In 1986 I moved from a large darkroom at work to a small darkroom at home and had this problem (I'd had no problem with the same enlargers/safe-lights paper etc before), then I read a magazine press release from Paterson/Photax who had introduced a Multigrade cover for their safe-light, essentially an OC/902 Amber brown dome filter to solve this issue - it did.

Essentially too much exposure fr has colour sensitised components. It's called the Herschell effect and has been know from the dawn of Photography, it's used in Direct Positive emulsions (inc Ciba/Ilfochrome) which are pre-fogged emulsions and when you expose the film/paper you are destroying some of the latent image.

So you might think your safe-light is safe, it's not fogging paper it's just destroying part of the latent image and dropping the potential maximum contrast.

Ian

 

[cliveh]

Do you have the dichro head switched on?

 

[ic-racer]

Oren, you and IC maybe onto something, i.e., I am not really clear what it is I am doing or, at the very least, I am not explaining it very well. I calibrated the head with combinations of yellow and magenta mainly so I would not have to retest exposure time every time I changed filtration. Perhaps I should have said that when combining yellow and magenta, I can't seem to get the contrast range I think I should have. Yes, I can use just one filter and get more contrast, but then the exposure time changes.

It is not always clear from the various calibration instructions, but if you want equal printing time form the ENTIRE range of contrast, your middle contrast values will have quite a bit of neutral density that you will be printing through all the time. By leaving the greatest contrast values out of your table (essentially Y=0 and M=Maximum), your overall printing times will be less in the entire table. Then what you need to do is have a "Filter Factor" for the highest contrast value. This is the analogy to Ilford's method whereby the highest contrast filters need a filter factor. Again this lets the commonly used contrast values (or filters) print with more speed.

So, maybe you have already done everything OK and you now just need to determine your special filter factor for Y=0 and M=Maximum and note that on your calibration table.

 

[RobC]

exact speed matching is a myth. For it to work you have to know the exact tone on the baseboard to know what is the fulcrum. Fact is you don't know it. You can only guess and infact that tone may not even exist in your neg and even if it does you have to be able to repeatably judge it accurately by eye.
So that means when you change grade you will never be exactly sure whether the time will be correct so there is always some tweaking of print time with a grade change. It simply isn't an exact science. It requires you the printer to apply your skill and judgment to nail it through visual assessment of the work print/print step wedge and a combination of both grade changes and time changes.

My bet is that the Y+M calibration that you did has not used the full range of what your filters are capable of. Speed point is useful as it minimises time changes if you can get your assessment of the speed point in the right ballpark but you simply won't be able to assess it really accurately when making a print. The process is more about thinking I need more print time and/or a change in contrast and not "this time is fixed and I'll get the perfect print with only changes in constrast from this point on".

My enlarger is speed matched but I can't ever accurately guess the exact print time and nearly always require a time change with a contrast change. I do it by using my eyes on my work prints and making an assesssment. The more you print the better you get at making those judgements. That is part of the skill in printing which can only be learned through repeated practice.

 

[Sirius Glass]

Exact speed matching does not occur across all grades.

 

[DREW WILEY]

I don't have time to read all the replies, but you could try a deep blue 47 filter below the lens. I doubt it will make any difference from maximum magenta. With some papers you have to have a token amount of exposure to both emulsion layers in order to get DMax overall.
Maybe a pinch of white light exposure, then heavy blue or magenta to deepen the blacks. I'd just ignore all that redundant "grade this, grade that" talk. You aren't using a graded paper, so why bother? Yellow or Green light exposes the low contrast emulsion, blue or magenta the high contrast emulsion. Don't mix them and life will be easier. Having to change your printing time is a non-issue. A simple test strip just takes a few minutes. Sometimes dichroic filters will "fade" in the sense that a certain amount of spalling off of the colored coating occurs due to heat after a number of years. You should be able to visually check for that, or for crud on the filters that warrants cleaning.

 

[kd7vdb]

I have the color head for my durst 601 and I had all sorts of issues using the color head (mainly 1.5 minute exposures with any good contrast). Switched back to the condenser head and filters.