G-Claron spec shows very low MTF?

Discussion in 'Large Format' started by greg_prior, Sep 15, 2003.

  1. I'm looking at the Schneider spec for a 150/9 and a 305/9 G-Claron.
    The MTF tables are plotted at 3,6, and 12 lp/mm. These lenses are
    best at f22 and a magnification of .5. But only show an MTF of 55-60%
    for the 150, and 30-50% for the 300 at 12 lp/mm. The MTF does look
    almost as good at infinity, but that's not saying much. Are these
    lenses really that bad? I was expecting a lot more for a 6-element
    design 'process' lens (like 50-60 lp/mm at 50%+).

    Does anyone have specs for comptetive 300 - 360mm small lenses
    (Nikkor 300/9, Fuji 300/8.5, APO-Ronar 300/9 etc.)? I kinda lost
    interest in this one. I want to use it with both film and a scan-back
    that has 84 pixels/mm (42 lp/mm).

    Thanks, Greg
     
  2. Rent, borrow or buy one and make photographs with it, I would never make a decision based on specs alone. The sharpest images I have were taken with 240, 270 and 305 G-Clarons
     
  3. Here we tested a 150mm f/9 Rodenstock Apo-Gerogon from a process camera at 1:10; its best aperture was F22. Our Schneider Componon was alot sharper in the same test; and its best aperture was again was F22. (35x45" original appears as a 3.5x4.5" image on the film) Our ancient Kodak Ektar 127mm F4.5 was 80 line pairs/mm at the very center; and only about 14 to 18 at the edges of the 3.5x4.5" test negatives; during the same tests..Process lenses are not the sharpest lenses around. We own four of them. My test above of the Gerogon was not in its design range; we tested for our own usage; at the 1:10 ratio that we required.
     
  4. Kelly, What were the tested results of the other lenses you mentioned?
     
  5. I'll extend this invitation to anyone who feels their photography is handicapped by one of those nasty G-Clarons---you can send your crummy old G-Clarons to me assured that you'll never again have to put up with it's embarrassing substandard performance again. If the lenticular offender is in a shutter, I'll even pay the postage!;-)
     
  6. Greg.

    I believe you can find what you need for the Rodenstock Apo-Ronar 300mm lens here:

    http://www.butzi.net/rodenstock/apo-ronar/p12.htm

    Hope this helps.

    DG
     
  7. My favorites too. On Chris Perez and Kerry Thalmann's tests a 150 G-Claron was seperating 76 lp/mm at f16 and a 305 G-Claron was doing 67!!! 67 for a 305! That's awesome. I love the stuff I make with mine.
     
  8. Our tests were done at a 1:10 ratio; for each of the the lenses I mentioned above. We had a requirement to shoot some maps, documents; and artwork; producing a 4x5 negative. The 4x5 camera was bolted to our super rigid process camera; and the test images placed on the rigid process camera's copyboard. We aligned the camera to be square with the copyboard; and shot many negatives. <BR><BR>The Apo Gerogon 150mm F9 peaked at F22 with a 2-3 reading which is 50 line pairs/mm at the very center. the edges of the test images were between 36 to 40 line pairs/mm<BR><BR>The Kodak Ektar 127mm F4.5 was at the center a 3-1 on the USAF chart at F16; which is 80 line pairs/mm . It was 2-5 at F22; which is 63.5 line pairs/mm at the center. It's peak was at F16; NOT f22; as I mentioned above by me from memory; not be my notes in front of me now.........The edges were sharper in the tangential numbers; like 36's...but about 15 to 18 in the radial numbers. Proper Engineering data quotes the lower of the two data sets. Thus the edges are about 15 to 18 line pairs/mm for the Ektar..This lens wasnt really made for 4x5; but for 3x4 cameras....But zillions of nice press shots were made with 127mm lenses; on 4x5 cameras<BR><BR>The Ebay mint 135mm F4.6 Schneider Componon-S peaked at F22 for overall performance at center and edge. At F22 was 2-5 in the center; for 63.5 line pairs/mm; and at F16 was 3-1 at the center; for 80 line pairs per/mm........BUT the edges at F22 were all 2-4 or 57 line pairs/mm.........at F16 the edges were between 50 to 40 line pairs/mm<BR><BR><BR>Probably with glass plates; the faster F16 or F11 might test better...But we used actual film; in our holders; in teh practical test of our lenses.....<BR><BR>Our test was basically a test between the Componon and the Apo Gerogon .....The Ektar was thrown in just for fun..We knew the edges would be weak......We tested the Gerogon where it is not supposed to be used...At a closer ratio like 1:5 to 1:2; maybe it would be alot better????? Well thats another test!
     
  9. The resolution measured does vary by the exposure of the negatives alot. We shot many at each aperture; and developed them immediately. Over-exposure ruins resolution many times. Real non-lab work is not so nice; and practcal results are usually lower. Many lense vary in performance ALOT with the magnification/reproduction ratio used. In comparing tests of Joe's verus Kilroy's; remember to try to get the actual magnification used for the tests. Many 35mm camera lenses are shot at 1:50 or 1:49 ratios.....Sometimes longer ones and MF lenses are shot at 1:25 ; just to get the shots; due to the longer focal lengths ; with a fixed test bench/wall/settup.<BR><BR>
     
  10. Greg: you are reading the wrong charts. The full opening MTF is practically irrelevant since at full opening the lens is used only for focusing. The MTF for the G Claron is excellent at f/22 and 1:2, almost as good at 1:1 and best at infinity. I prefer the Apo Ronar however although it is a slightly lower contrast lens but extremely sharp. Also it is smaller and lighter than the G Claron. Additionally it boasts of almost zero distortion at close distances, no other lens available today does that that I know.
     
  11. I'm with Jim on this one. The thing produces tack-sharp pictures, is easy to carry and never runs out of coverage, on 5x4 at least.
     
  12. Wow, what a bunch of great responses.

    It sounds like Kelly's tests show that similar lenses perform better than the G-Claron spec. But maybe their specs are better than the G (although it doesn't seem likely that a 3-element would out-perform a 6-element lens). So this doesn't explain the G-Claron data.

    Julio thought I was reading the wrong charts, but I'm look at the ones on the right labeled f/22 at infinity and conjugates of -2 and -1. The MTF is only 12 lp/mm at 40% to 80% over the entire 4x5 field.

    David routed me to the APO-Ronar 240mm data (couldn't find 300 mm data, but it's probably similar). It is better than the G, but no by much. It is only 20 lp/mm at 40% to 65% over the 4x5 field.

    Jim mentions the Perez/Thallman test results, but I think they state that their results are comparative, not absolute. They certainly are a lot different than what the manufacturers specify. None of my lens designs have measured 3x to 4x better resolution than the simulation results. But still the G compares well with other lenses tested by Perez/Thallman that are well regarded.

    I did some more research and it turns out that the best lens performance I can find is at 20 lp/mm on the likes of APO-Symmar L, and APO-Sironar S. So I am guessing that the numbers reported by Perez/Thallman are at a very low MTF, maybe even 0% to get such a high spatial frequency. The same with Kelly's results.

    Jeffrey might have the right idea. Try it and see if 12 lp/mm is 'good enough'. Obviously it is for a number of users.

    Is the G-Claron a 'dog' at 12 lp/mm? Maybe not, but it looks like the APO-Ronar (a 4-element design - go figure!) has almost twice the resolution. I wish I had data on the Nikkor 300/9, Fuji 300, etc. A factor of almost 2 in resolution is pretty significant.

    Now if I could just get lateral color data...

    -Greg
     
  13. Greg,

    Sorry about the link I posted being for a 240mm Apo-Ronar. I've tried finding one for the 300, with no luck.

    DG
     
  14. Please send me your 305 & 355 G-Clarons if they are not up to your standards, I will gladly use them in my little world of LF. My 240 on 8X10 is very sharp.
     
  15. you can't go by a chart for selecting a lens....the lens
    manufacturers have to protect there more expensive lines.

    schneider claims "much larger coverage" with a symmar-s lens
    over a symmar lens....and if you go by their provided charts it
    does. when you dig a little deeper and see the tiny tiny print
    which points out that the symmar-s (and apo symmar, and
    probably now symmar-l) coverage was measured at F22 and the
    older lens was measured at f16.

    If schneider told you in charts that the g claron performed AS well
    if not BETTER than the more costly "new design" lens...which
    one would you buy??? They also claim that it performs poorly at
    inifinity and barely covers 4x5 at infinity at F22. if that is the case,
    how come I can shoot 5x7 with mine at infinity at F22, and shift
    the mother all over the place.

    For the amount of time you can spend anaylizing charts, you can
    buy a 150mm G Claron (I paid $191 for one from Jim Galli) shoot
    5 test sheets, examine your prints, and make a decsion. If you
    don't like- sell it- you will get your money back.

    If anything, the apo symmar 150mm 5.6, gets blown away by the
    lowly 150mm F9 G Claron. The apo lens runs out of coverage
    so quickly it is not funny. Also, its close up performance to put it
    frankly- sucks. A lens that will work at high mag ratios without
    fringing, and be a wide angle for 5x7 with coverage to boot for
    $191.00??? Where does it say that on the chart??? When you
    really think about it, has any lens made in the last 30 years "not
    sharp" on 4x5???
     
  16. James- Thanks for the reply. You make a number of good points, but I don't believe that a reputable lens company would falsify technical data like MTF figures for some 'marketing' reason. They design new lenses because they can make them better than the old ones.

    I'm not really too concerned with coverage specs since I don't do a lot of movements (my topic was just MTF). The data sheet says the 150mm (I think that's the only lens you were talking about) is tested out to 189mm. At f/9 you can see that the MTF starts to fall off considerable. At f/22 there is still MTF to burn, so it obviously carries a pretty good MTF past the 189mm spec. Of course you can use the lens out to any MTF value you choose. In my case, I need 42lp/mm, and would like that out to the corners of 4x5.

    As far as time/money spent to analyze lenses, you are right. Since all lenses vary from their spec, I should buy one of each, test, and sell off the excess. I am looking for a 300 to 360mm lens, and have found over a dozen lenses is this size (both new and old). For a few thousand dollars and a few days time I could get data on the whole lot, then spend a few more days selling off the excess. I'd rather eliminate the ones that won't meet my requirements, and save a lot of time and money. I trust the manufacturers MTF specs for this.

    I guess in general we are talking about different things. I am interested in a sharp lens for mostly on-axis distant use with a 4x5 scan-back. You are interested in close-up, 5x7, and coverage (or defending the G - both are fine). The G-claron may excell in all these areas, but they are outside my area of interest. I'm not saying the G is a 'bad' lens, just that there are better candidates for my purposes, and that I was surprised that a 'process' lens would only resolve 12 lp/mm at 50%+ when I was expecting 40+ lp/mm. Obviously the 12 lp/mm is more than adaquate (you're right, the spec sheet doesn't say this) for a lot of LF shooters, whereas I though >40 was needed.
     

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