Newbie help with C700 enlarger

[fschifano]

There's definitely an argument to be made for keeping this enlarger simple. It's a relatively small machine and you're not likely to find a dichro head for it that fits your budget. There's noting wrong at all witha dichro head, in fact I prefer working with one head for all the reasons mentioned. Calibrating a dichro head for the different settings is pretty easy if you have a 31 step transmission step wedge like this. Just match up the middle value and see where it falls in relation to a contact print of the wedge with no filter. Easy peasy. Each step on the wedge is exactly 1/3 stop darker or lighter than it's neighbor. Say you have a print made with no filter and you like the overall exposure, but decide that it needs a little more or less contrast. Simply take out the little contact prints of the step wedge and match up the midtones with the step wedge and see how much more or less exposure will be needed to keep them there. If you have an enlarging meter, it's even easier. With this data you can also see where the rest of your values will fall with changes in filtration.

But as you're beginning to see, it's possible that you can find a 4x5 enlarger for not much more than the cost of finding a dichro head for this smaller enlarger, and in the end you'll have a much more robust machine. Don't get me wrong. The Omega C700 is a good enlarger, but it is not a high end machine. I got a B600 (just a little smaller than the C700 and good for up to 6x6) for nothing because my neighbor was going to throw it out when he moved. He couldn't sell it at a price that was worth the trouble for him to do so. I got a Beseler 45 MXT with a cold light from a guy for that same reason, and because he wanted it to go to someone who knew how to use it and would appreciate it more than he wanted the money. Moral of the story is the C700 isn't worth the expenditure in my mind. Use it with a set of VC filters made to fit the filter drawer. You'll be happy with it until your needs change. I worked like that for a very long time until my first 4x5 enlarger (an Omega D4) came along with a dichro head. Then if you like, look around for something better. Keep your eyes peeled and something will come along.

[Zer0s0phT]

Thanks for the great info!

I just purchased my Ilford filters and should be getting the rest of my equipment this week. I scan the auction and classified sites all day so your right, I will just have to hold off for a deal on a nice 4x5. Thanks for the link, I will keep it bookmarked for when I do get a dichro.

[fschifano]

Get the step wedge. The claims of constant exposure over a wide range of filters doesn't always hold up. It is based upon using Ilford's papers with a tightly controlled light source of a given color temperature. Use a different manufacturer's paper, and the exposures can and often do change. Sometimes there are variations in a single manufacturer's product that can make a difference. Maybe the light bulb in your enlarger is running a little hotter or cooler than the standard and your exposures will change. Trust me on this one, I've seen it. I have three enlargers running right now and none of them deliver the promised constant exposure. They all work, and they all work well with the exception of the cold light on the Beseler; but that's another story of no concern to you at this point. The point is that they all need some sort of exposure compensation for the different filters in the set.

If you have the step wedge you'll know exactly how much compensation you'll need. Each time you get a new batch of paper, make a contact print of the step wedge with enough exposure so that the first step, just a hair lighter than pure black, falls around the #12 step with no filter in the enlarger. Then using the same head height, aperture, and exposure time, make a contact print of the step wedge using each of the filters in the set. Knowing that each step is exactly 1/3 stop lighter or darker than its neighbor, you'll be able to see how much more or less exposure you'll need by matching up the mid tones, and, as I noted earlier, you'll be able to tell where the other tones fall with a change in filtration. In my opinion, the step wedge is one of the most valuable tools I have in the darkroom. It saves me a whole lot of wasted paper and makes choosing the right grade a lot easier because it removes most of the guesswork.

[Zer0s0phT]

Got it, it sounds extremely useful. I will be ordering tonight. So I would be compensating slightly for exposure changes in all grades of filters, instead of Ilfords statement of the same exposure for 00-3 1/2, taking out all other factors like light intensity etc.? Does there become a point where you have a standard exposure time for the initial print of the wedge, Or is that the guesswork still involved? Would you print 12 test strips using each 1/2 stop filter grade for each new batch of paper based on using the same filters, or just 6 in full stop increments?

Thanks for the great info, this tool is actually helping me understand the process of figuring out the proper exposure better.

[fschifano]

Got it, it sounds extremely useful. I will be ordering tonight. So I would be compensating slightly for exposure changes in all grades of filters, instead of Ilfords statement of the same exposure for 00-3 1/2, taking out all other factors like light intensity etc.? Does there become a point where you have a standard exposure time for the initial print of the wedge, Or is that the guesswork still involved? Would you print 12 test strips using each 1/2 stop filter grade for each new batch of paper based on using the same filters, or just 6 in full stop increments?

Thanks for the great info, this tool is actually helping me understand the process of figuring out the proper exposure better.

Some papers are faster than others, but they're mostly all within a stop or so of each other. What might surprise you is that for a given paper, the apparent speed with one type of light source can be markedly different when you switch to a different light source. To keep the explanation simple, let's take a look at fixed grade papers. Fixed grade papers are very sensitive to blue light and less so to other parts of the visible spectrum. The cold light on my Beseler enlarger is optimized for graded papers and glows with a distinctly blue case, but does not appear very bright on the baseboard. If you measure it with a meter, it shows decidedly less bright than the incandescent and halogen lamps of my other two enlargers. Yet it prints blazingly fast with fixed grade papers. Why? The output of the lamp is heavily biased towards the blue end of the spectrum, precisely where the paper is most sensitive. The blue end of the spectrum is rather poor from incandescent lamps and all that light energy is for naught, since the paper can't really see it to well.

The biggest difference in speed between different types of variable contrast papers will be if you are comparing a neutral to cold tone paper against a warm tone paper. Warm toned papers are a lot slower in general, sometimes as much as two stops slower than a neutral toned paper from the same maker. It's the nature of the beast.

It shouldn't take long to figure out a good starting point for the initial unfiltered print of the step wedge. The first print of the step wedge will probably be off. Figuring out how much more or less exposure you need is as easy as counting the steps since the wedge is incremented in 1/3 stop intervals. Need to move it up or down 3 notches? Double or halve the exposure. See the attachment for compensation factors. The table goes from -4 to +4 stops of compensation by time. Simply decide how many stops you want to add or subtract, look up that number in the "F stop change" column and multiply your exposure time by the factor in the "Comp Factor" column. Don't change anything else. Change only the exposure time.

I print a copy of the step wedge for each filter in the set, including the 1/2 grades. You'd be surprised where the changes fall sometimes. It doesn't take much paper to do this, but it does take a bit of time. If you're using 8x10 paper, you can cut 10 strips from each sheet, each 1x8 inches. That's more than enough to print the step wedge. You need 13 strips altogether, but cut 20, because you'll need a few to dial in the initial exposure and to allow for the inevitable mistakes. Mark each one on the back with the filter number. Mark the strip made with no filter stating so, and include the head height, aperture and exposure time for reference. Once you have that dialed in for one paper, most other papers will come close to that - usually within a stop.

This is really a lot less complicated than it might appear to be. Once you actually get a visual on how this works, it will become almost intuitive.

[Zer0s0phT]

It does make perfect sense, I am glad your explanation is in depth enough but still comprehensible to me since I haven't actually printed and seen the results yet. This is a huge help and I cannot thank you enough for taking the time to explain this. I have printed the attachment and it will be having a permanent place in my darkroom. If this forum had a rep system, I would max you out

Thank you again

[ic-racer]

One of the very nice thing about Multi-Grade contrast filter is that they are calibrated. For example, if you start out with #2 filter, which is pretty much standard, and wish to increase contrast, you can just stick in #3 and not make exposure time adjustment. If you want less, place #1 and use the same time. Of course, small change may be needed but you'll get used to it very quickly. This is true until you get to #4. Then, you'll have to double the time.

This is not true with Dichro head. Each time you change the setting to change contrast, you'll have to redo the exposure timing. You may get used to it but the process is very complex.

Actually the chart that comes with the Ilford Paper gives filtration values that provide a constant exposure across settings. As good as the filter set. I have tested them side-by-side.