Minolta C.E. Rokkor f/5.6 vs Rodagon f/5.6?
I've been using the Minolta CE Rokkor for a while now, not sure if anyone else has experience with it. Along with some small, but frustrating alignment problems, I've never been hugely impressed with the sharpness of this lens - even at my small standardised print size of 6". Other than high quality reproductions of medium format images however, I have very little to go on in comparing the definition of my prints - theoretically my images could be much sharper than I have the experience to determine.
Does the Rodagon have much higher quality optics than the Minolta? Will there be a noticeable improvement in sharpness if I upgrade to this lens?
My other option is the Schneider Comparon-S 80mm f4.5.
Last edited by batwister; 04-08-2012 at 11:35 AM. Click to view previous post history.
What is the format and focal length of your lens? You spoke of your standardized print size of 6”. Is that width, length, diagonal? This information is needed so that we can figure the magnification and compare that to the useable range specified by the maker. Use a lens outside of its specified magnification range and the image quality might suffer. That’s not a design defect, just using the wrong tool for the job.
In making small prints outside of the recommended magnification range for the lens you’d customarily use, you’ll get better results using a shorter lens that covers the film and is within its specified magnification range.
Rodagons and CE Rokkors are both 6-element 4-group enlarging lenses capable of excellent results. I’d expect little if any discernible difference assuming that both lenses are clean and in good condition. I believe that the “CE” of CE Rokkor lenses designates “Color Enlarging” where it’s assumed that greater accuracy is necessary for good results with color printing as compared to B&W printing. At least that used to be a commonly held opinion years ago. I believe that the CE Rokkor enlarging lenses were made in 2.8/30mm, 2.8/50mm, and 5.6/80mm.
I find it difficult to access the optical performance of an enlarging lens by viewing small enlargements. Better to raise the head as far as you can for maximum magnification (within the maker's specifed usable range) and make a print—even a small one—of an important area. Do this with two different lenses you wish to compare to see if there is a meaningful difference. They will likely give similar if not identical results.
Here are a few opinions on the CE Rokkors.
Many of us have similar favorable opinions of Rodagons or any other high-grade 6-element lens.
Did you buy the lens new? Has it ever given good results? If it is a "used lens" there are a myriad of ways it could be buggered. Especially if it came from e-bay.
Originally Posted by batwister
In general, a properly performing Minolta C.E. Rokkor 5.6 would give identical results to just about any of the other 6 element lenses out there at small reproduction ratios (less then 7x).
Are you using a glass carrier with one or two pieces of glass?
6" measured by width (from 6x6 negs) and the focal length is 80mm.
Originally Posted by Ian C
Thanks for the info.
Bought from a pretty reputable second hand dealer in the UK, along with my enlarger. Glass carrier, two pieces. I've had somewhat better results with a slightly larger 8" print, but it's difficult to say whether this is down to a lack of diffraction, as the negative was made at f11 rather than my usual f/22. It never occured to me that an enlarging lens would produce meager results with a marginally smaller magnification - from 8 inches to 6.
Originally Posted by ic-racer
I've read of quite a few square format photographers standardising at 8" prints, maybe this is an optimum size, as much as it is a fine art 'small is beautiful' mentality. Perhaps I've just gone a bit too small.
Last edited by batwister; 04-08-2012 at 01:24 PM. Click to view previous post history.
Assuming a 6.25” or greater projection width, that gives at least 2.9X. That’s within the 2X-10X magnification range stated by Rodenstock for its late model 4/80mm Rodagon. That should be identical for the 5.6/80 CE Rokkor.
If there’s nothing wrong with the lens (most likely the case), then any dissatisfaction with the print quality is due to some other factor. In the cases I’ve investigated, the cause is most often the negative moving during the exposure as it absorbs heat from the light passing through it. We counter this with a heat-absorbing glass filter, a glass carrier to keep the negative flat, or both.
The negative heating I refer to usually only results in the negative getting somewhat warmer than the surrounding part of the negative held by the carrier. It doesn’t take a great deal of temperature difference to make the negative move out of the shallow depth of focus about the plane of focus.
Most enlarging lenses produce their best image quality closed 2-3 stops.
Last edited by Ian C; 04-08-2012 at 01:40 PM. Click to view previous post history.
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Thanks Ian and yes, I try to leave the lamp on for a little bit, then focus, to avoid popping.
What about the phenomenon known as 'decentering' that I've just been reading about? Could this be a potential problem with the lens?
I’m not sure what you mean by “decentering”. I suppose that it might refer to the lens being assembled with an off-center element.
I don’t believe that Minolta or any other major maker ever allowed a lens with such a defect to leave its factory. Its quality control was as perfect as can be devised.
If you mean that the lens isn’t centered over the negative, I don’t think that can happen unless the carrier is makeshift. The maker’s carrier should be well centered over the lens. Likewise, the lens should be in the correct position so long as it’s installed in the enlarger maker’s lens mount and not in some jury-rigged affair.
I suggest that you try the following to diagnose the problem:
Place your film into a glass carrier. If you don’t have a glass carrier, get two identical pieces of window glass cut to the size of the carrier, de-burr the edges with a fine whetstone to prevent scratching the negative, place the negative into the temporary carrier (the glass must be perfectly clean) tape the edges with black tape to prevent light spill.
Put the negative in the glass carrier or temporary glass carrier into the enlarger. Raise the head all the way up, focus carefully on the grain, and make a print—even a small one will suffice—at the optimum aperture of f/11 (for an f/5.6 lens) Critically evaluate the fine detail and contrast of the print. The negative was held flat between the two sheets of glass so it can’t “pop”.
Make certain that the timer isn’t somewhere where the force of triggering it can start the column vibrating.
Any lack of sharpness must be due to the lens, focus error, or vibration or movement of the enlarger during the exposure. If you prevent vibration and you’re certain that the grain focus was perfect, then what you see in the print should be strictly due to the lens and the image quality of the negative.
If the bottom surface of the upper glass isn’t anti-Newton you might see Newton rings on the print, but that won’t prevent evaluating the projection quality of the lens.
I have a plethora of enlarging lenses and the Rokkor is one of the best, definitely better than the Rodagons and Componons.
You probably have an issue with focusing if a 6" print is not sharp. You might also be stopping the lens down too far since your print size is so small and the resulting diffraction is killing the sharpness of the lens. Keep the lens around f/8.
How can you "upgrade" to a Rodagon if you do not know if the optics are of higher quality than the Minolta? Kiku
Originally Posted by batwister