Minolta C.E. Rokkor f/5.6 vs Rodagon f/5.6?

Discussion in 'Enlarging' started by batwister, Apr 8, 2012.

  1. batwister

    batwister Member

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    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.

    Thanks.
     
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  2. Ian C

    Ian C Member

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    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.

    http://www.greenspun.com/bboard/q-and-a-fetch-msg.tcl?msg_id=000olI

    Many of us have similar favorable opinions of Rodagons or any other high-grade 6-element lens.
     
  3. ic-racer

    ic-racer Member

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    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.

    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?
     
  4. batwister

    batwister Member

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    6" measured by width (from 6x6 negs) and the focal length is 80mm.

    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.

    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.
     
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  5. Ian C

    Ian C Member

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    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.
     
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  6. batwister

    batwister Member

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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?
     
  7. Ian C

    Ian C Member

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    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.
     
  8. Ian C

    Ian C Member

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    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.
     
  9. M. Lointain

    M. Lointain Member

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    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.
     
  10. kiku

    kiku Subscriber

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    How can you "upgrade" to a Rodagon if you do not know if the optics are of higher quality than the Minolta? Kiku
     
  11. batwister

    batwister Member

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    The Rodagon seems, generally, to be more expensive. I bought the Rokkor from the same dealer who has a Rodagon f/5.6 listed at twice the price.
    Would I be paying for the name/build quality? The fact that this lens is simply more popular?

    Yes, that's what I was referring too. I'm not talking massive uniformity issues, but right up close, the bottom area of my prints are noticeably less sharp. To another viewer, who knows, and maybe I'm being too finicky.
    I'm pretty sure this is down to slight alignment issues though, with which I'm still battling.

    The sharpest area of the print (where I've focused) is what I'm concerned with here however.
    Like I say, compared with high quality book reproductions of other medium format images (namely, Fay Godwin and Robert Adams - both Hasselblad shooters) the sharpest areas of my prints don't have the same definition. I can't imagine what the original prints are like in that case.
     
  12. michael_r

    michael_r Subscriber

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    Batwister, when you evaluate the sharpness you perceive in your prints, do you have other reference points besides the high quality book reproductions you mention?
     
  13. batwister

    batwister Member

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    No, but I think I'd certainly do well to acquire some prints.
     
  14. GregY

    GregY Member

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    Some of your issues may stem from the alignment or misalignment of your enlarger....lens / negative carrier etc....
     
  15. michael_r

    michael_r Subscriber

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    I agree - because you will likely be disappointed in their sharpness compared to the versions in high quality books. I know this sounds counterintuitive, but I've spoken about this in various threads.

    Don't get me wrong - I'm not suggesting you should stop looking for ways to improve and maximize print resolution (alignment, lenses, glass carriers etc). On the contrary, I'm obsessive about that stuff. But be careful comparing prints to those ultra-sharp, silvery, crystal-clear, jewels-like reproductions we see in fine books. It's not that they actually have more resolution than the original prints (which is obviously impossible), rather that there is something in that reproduction process that seems to enhance micro-contrast and the impression of edge sharpness.

    Michael
     
  16. batwister

    batwister Member

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    I would assume this has something to do with the downscaling of those reproductions? i.e. diffraction for instance would certainly appear diminished (same concept as reducing the resolution of a blurry digital image, which will then appear sharper in its smaller size). But what about images reproduced 1:1, like those in Michael Kenna's books? Surely what I see here is more faithful and any flaws are amplified? This is getting into the risky territory of perception, but I may well be mistaking sharpness for acutance. I can understand that acutance and edge sharpness might be augmented in reproduction, where level of detail falls down. This makes comparisons confusing.

    I only have the cheaper retrospective book of Michael Kenna's (Images of the Seventh Day), in which the larger images are 1:1 (about 8") and certainly compared with these, my prints generally appear to have more depth of detail, but perhaps not the acutance. He shoots higher speed film, which will of course have something to do with this too, as the grain makes edges appear sharper. There's also the fact that most of my images are made on overcast days where diffused light means textured areas of a scene appear softer than they would in direct light, but I only compare my prints with images made in similar flat lighting.

    I'll have to take a section of a print to a gallery and compare it with the images on the walls.
     
  17. MattKing

    MattKing Subscriber

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    On the subject of "sharpness", if you haven't already done so, I would strongly recommend reviewing the appropriate sections of Ctein: "Post Exposure"

    http://ctein.com/booksmpl.htm

    For that matter, there are a whole bunch of other sections of that excellent resource you might want to read.
     
  18. michael_r

    michael_r Subscriber

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    You got it right, perceived sharpness is a tricky thing. Resolution is only one of the components. There's also edge acutance, contrast/micro-contrast and graininess. And of course the size of the original negative. High quality reproductions often appear to me to have enhanced micro-contrast, a kind of subtle unsharp mask effect. I'm no expert on the process, but it seems to me somewhere in those laser scan duotone or tritone processes you end up with that. Not an overt effect, but just enough to give a heightened impression of sharpness. It seems to me to have less to do with the reproduction ratio, as I have always seen the same thing even in fairly large reproductions such as those on some Ansel Adams posters, etc.

    Anyhow I guess this was getting into a whole other complicated topic. Just thought it was worth throwing out there as something else to keep in mind because I remember when I finally saw original prints by Ansel, Weston, Sexton etc, as beautiful as they were, even contact prints did not have quite the crystal clarity I knew from the books.

    All that aside I think you're on the right track in trying to identify and address the various variables (negative stage, lens and baseboard alignment, negative flatness, lens quality, vibration, focusing). Here are two more to keep in mind (although #2 is only if you're really nuts - like me): 1) Possibility of focus shift when stopping your particular lens down. 2) Quality of the carrier glass, particularly below the negative.
     
  19. batwister

    batwister Member

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    Thanks very much for the link, Matt.

    John Sexton's Recollections really is somethig to behold, so I can certainly believe this is true.
     
  20. michael_r

    michael_r Subscriber

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    That's a pretty good example. I have that book, and I also have a dozen original prints by him, a few of which are in that particular book. The real prints are just incredible of course, but yeah those reproductions in the book (and his other books) have that extra crisp silvery look you only find in books.