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Schneider 60XL on 60mpx chip (Credo60/IQ160 etc) samples
- Thread starter tjv
- Start date
100% crops with H4D-50, 6 micrometer pixels. Normal USM sharpening applied, same processing on all crops. No lens corrections etc.
AreBee
Member
Anders,
If anything, what we saw from Alpa was that the quality control process is most often a combination of precise measuring equipment, but also that the human component is a participant in almost all aspects. This was especially the case when it came to lens evaluation. First, the lenses are intended to be dialed into an infinity setting, and when turned all the way to that mark, represent the sharpest image quality for an object at a significant amount of distance from the lens, in excess of a kilometer, in Alpa’s case. This is an essential value and benchmark for the lens to exhibit sharply. Alpa captures the center and left and right sides of each lens they receive into inventory with an 80 megapixel digital back. If the infinity target at the top of the distant peak isn’t visible because of low hanging clouds, the delivery of your lens could be delayed due to the weather!
The results are then evaluated on an Eizo LCD and compared to reference files for the same lens shot with that same 80 megapixel digital back unit. There is some serious eyeballing involved and we all took part in this. What immediately was obvious is that no two lenses are exactly the same. And this is not surprising. Lenses, after all, are comprised of natural elements that then go through a cooking process and, once assembled into a housing, are susceptible to environmental changes. Out of the batch of 20 or so lenses we evaluated files from, we interestingly found that 2 of them noticeably exceeded the reference files and 2 of them noticeably did not come close to that level, and the 2 latter lenses were referenced as “go backs”. The remaining lenses were very close to the target performance. So what does this mean? It does mean that a lens purchased from Alpa will always be at a certain level of quality. And that a lens purchased generically may be below that quality level, if the luck of the draw doesn’t favor you.
Credit: Steve Hendrix
Due to the variable nature of medium format digital sensors, high quality optics, and the movements a user might want to inform the components with, we find ourselves in an evaluative and educational position with our clients on a daily basis. Sensor position within the image circle of a lens brings about situations where limitations are revealed, and flaws exposed. Part of prescribing the right combination of these products is a thorough understanding of the performance. What we were truly interested in was how Alpa evaluates the lenses they receive from Schneider and Rodenstock, and does their evaluation offer any advantage over buying the same lenses off the shelf?
If anything, what we saw from Alpa was that the quality control process is most often a combination of precise measuring equipment, but also that the human component is a participant in almost all aspects. This was especially the case when it came to lens evaluation. First, the lenses are intended to be dialed into an infinity setting, and when turned all the way to that mark, represent the sharpest image quality for an object at a significant amount of distance from the lens, in excess of a kilometer, in Alpa’s case. This is an essential value and benchmark for the lens to exhibit sharply. Alpa captures the center and left and right sides of each lens they receive into inventory with an 80 megapixel digital back. If the infinity target at the top of the distant peak isn’t visible because of low hanging clouds, the delivery of your lens could be delayed due to the weather!
The results are then evaluated on an Eizo LCD and compared to reference files for the same lens shot with that same 80 megapixel digital back unit. There is some serious eyeballing involved and we all took part in this. What immediately was obvious is that no two lenses are exactly the same. And this is not surprising. Lenses, after all, are comprised of natural elements that then go through a cooking process and, once assembled into a housing, are susceptible to environmental changes. Out of the batch of 20 or so lenses we evaluated files from, we interestingly found that 2 of them noticeably exceeded the reference files and 2 of them noticeably did not come close to that level, and the 2 latter lenses were referenced as “go backs”. The remaining lenses were very close to the target performance. So what does this mean? It does mean that a lens purchased from Alpa will always be at a certain level of quality. And that a lens purchased generically may be below that quality level, if the luck of the draw doesn’t favor you.
Credit: Steve Hendrix
GrahamWelland
Subscriber & Workshop Member
True, but then again you'd also expect Schneider & Rodenstock to do the same level of QC BEFORE shipping to suppliers like Alpa who then mount them on helicoids or lens boards. :banghead:
Thanks for the interesting info about ALPA testing. So what they do is a 30 minute test and then send the lens back to the manufacturer if it wasn't good enough compared to the average -- which in this case was 1 out of 10, rather than taking it apart and re-mounting it with more precise shimming. Such a test would raise the cost of say 100 euro per lens, and the lenses are obviously much more expensive than that so I think one can conclude that you mainly pay for the helicoid mount. However the value to the customer not having to make this test for themselves can be much much more than 100 euro...
I wonder what happens with the lens sent back. Are they re-mounted with better precision, destructed or resold to some other which haven't their own extra QC like ALPA? My guess is that they are simply retested and resold, as Rodenstock/Schneider surely have their own QC of the automated measurement kind but with higher tolerances than ALPA. 1 out of 10 bad copies would for most products be considered a very poor result, so the only reasonable explanation is that the manufacturer have wider tolerances.
If they are resold without further action it means that non-ALPA lenses are bad more often than 1 out of 10...
I wonder what happens with the lens sent back. Are they re-mounted with better precision, destructed or resold to some other which haven't their own extra QC like ALPA? My guess is that they are simply retested and resold, as Rodenstock/Schneider surely have their own QC of the automated measurement kind but with higher tolerances than ALPA. 1 out of 10 bad copies would for most products be considered a very poor result, so the only reasonable explanation is that the manufacturer have wider tolerances.
If they are resold without further action it means that non-ALPA lenses are bad more often than 1 out of 10...
GrahamWelland
Subscriber & Workshop Member
The thing is that you know that every lens leaving Rodenstock or Schneider or any manufacturer is checked on a collimator. What obviously is true is that perhaps the tolerances applied by the lens manufacturers doesn't match either resellers or even customers. How else would these differences between spec lenses and poor field copies occur?
I'm sure that Alpa's rejected lenses are all within manufacturers specs.
I'm sure that Alpa's rejected lenses are all within manufacturers specs.
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Yes I too find that to be the only reasonable explanation, otherwise 1 out of 10 bad would be a total failure of the manufacturing line.
The follow-on question is then why is the tolerance set this wide. I'm 100% certain that the desire among customers using this type of gear is to get a lens that is very close to the theoretical maximum. Is it because the manufacturers simply aren't capable of better precision, or that it would cost too much, or make lenses too delicate?
danlindberg
Well-known member
I have or have had: SK 28XL, Rod 32HR, SK 35XL, SK 60XL, SK 72L, SK 90N, SK 120N
None have shown, atleast what I have been able to detect, weakness left to right sharpness. I had the SK 35 recalibrated for infinity but that is the only one and came back a razor.
None have shown, atleast what I have been able to detect, weakness left to right sharpness. I had the SK 35 recalibrated for infinity but that is the only one and came back a razor.
All in ALPA mount I suppose, and as said they make an extra QC step. Not sure how large shifts they test though. The problems seen on these SK60XL is in the outer range of the image circle.
Personally I have only experienced problems with the SK60XL, and I have 35, 47, 90, 120 and 180 too, all those second hand by the way, some which I have mounted myself. Ironically the only one I bought new was the one with problems
. However the 60 XL is also the one I have tested the most and the one with highest expectations. The 47 has some serious falloff too to the edges of its huge image circle, but it's an old analog design so it still matches my expectations.
Personally I have only experienced problems with the SK60XL, and I have 35, 47, 90, 120 and 180 too, all those second hand by the way, some which I have mounted myself. Ironically the only one I bought new was the one with problems
. However the 60 XL is also the one I have tested the most and the one with highest expectations. The 47 has some serious falloff too to the edges of its huge image circle, but it's an old analog design so it still matches my expectations.Thanks for the summary, Torger. It seems a good sample 60xl is king, but how do you know you'll receive an optimal copy of it (let alone any other lens, I guess.) in real world shooting and using a CF I'm finding the RS55 good enough, so long as I'm not needing perfect edge to edge sharpness in my panoramas. I wish I had money to spend though, I'd sure appreciate that extra detail to the corners.
The thing I have most difficult to accept is that Schneider-Kreuznach said they couldn't remount the lens even if I paid for it. With my Linhof body and my digital back I can send it in for service and recalibration at a fee, no questions asked They take it apart and put it together again to the best possible precision they can.
This means if you happen to get a lens that's in the outer range of the manufacturer's tolerance there's no way to improve on it :banghead:
I've got to see yet another left-right pixel peep of an SK60XL (or rather upright/upside down mount) at ~100mm image circle, and that was a good copy (ALPA by the way) both sides looked about the same as the good side on my loaner lens. So there are copies of this lens that is really excellent.
Just my luck to get two in a row that aren't. I thought several times about maybe it's I that makes something wrong in testing but the mounting test is really robust against other errors, if there is camera skew and lens is perfect the error shouldn't change when rotating the lens 180 degrees, so I can't think of any other error...
Anders, if, when you get your lens back, you are still unhappy with the performance then - assuming you still have the loaner to hand - simply unscrew and swap around the rear groups of each lens and test. I’ve done this before a couple of times with lenses and the performance of one lens has always improved, especially towards the outside of the IC. On one occasion, it was a dramatic difference. If you have a spare Copal 0 shutter you could also play around with different front and rear groups on that.
Jim
Jim
My one experience with S/K / Alpa didn’t exactly leave me enamored with their quality control. Sent three lenses via a dealer to Alpa for remounting. S/K does this, so they forwarded them. When I got them back there were obvious issues with a couple of them. The packing of the lenses left a lot to be desired as well; they had simply reused my original packing without removing foam to account for the additional helicals and mounts, so everything was crammed in really, really tight. This all said to me that no one at S/K checked the work done, and that subsequently the lenses were never inspected by Alpa or the dealer I used. Given the cost, this was disappointing to say the least.
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So to get this straight...
1: Alpa gets sent lenses to select, rejects a few and send all back to SK to mount in helical.
2: SK then unscrew the lenses from shutter and mount in helical.
3: SK send on lenses (back to Alpa, or to dealer?) who most probably doesn't repeat same rigorous tests. (A dealer doesn't have such complex machinery to measure things and can't be expected to.)
Seems a bit silly to me, but perhaps I'm missing something?
1: Alpa gets sent lenses to select, rejects a few and send all back to SK to mount in helical.
2: SK then unscrew the lenses from shutter and mount in helical.
3: SK send on lenses (back to Alpa, or to dealer?) who most probably doesn't repeat same rigorous tests. (A dealer doesn't have such complex machinery to measure things and can't be expected to.)
Seems a bit silly to me, but perhaps I'm missing something?
AreBee
Member
Anders,
Example: On the occasion that Steve Hendrix visited Alpa, perhaps the 20 lenses being tested were from a production run of 200 lenses. If the Schneider Lemon Rate (SLR[sup]TM[/sup]) is 1:100 then two production lenses could reasonably be expected to perform outside of specification. Both could have been included in the Alpa shipment.
Your explanation is reasonable but it is not the only reasonable explanation.
Not necessarily.
Example: On the occasion that Steve Hendrix visited Alpa, perhaps the 20 lenses being tested were from a production run of 200 lenses. If the Schneider Lemon Rate (SLR[sup]TM[/sup]) is 1:100 then two production lenses could reasonably be expected to perform outside of specification. Both could have been included in the Alpa shipment.
Anders, I will do a test for you with my RS55 and 70mm lenses, hopefully tomorrow, to show you just how good / bad they perform at such movements. When I tested the 55 on a flat subject when first getting my Credo (not using CF which I didn't have then) I came to the conclusion that it was less than good off centre, maybe unusable. I was really disappointed. However in real world use, with CF, I'm mostly happy with it, although would very much appreciate the supposed better performance out to the edge of frame of the 60xl.
Not quite - S/K mount the lenses in their helicals and then on the Alpa mounts; they then send them to Alpa who carry out their own QC* before sending on to the end user or dealer.
By the sounds of it, this doesn't happen if you send a lens to be retrofitted. It's simply sent to S/K via Alpa before being returned to the dealer once the work is done. I can possibly understand that because - from their perspective - they are dealing with a used lens. They would need to test it before sending to S/K and then again on receiving it back, in order to make sure performance hadn't deteriorated. Could get tricky. Still, given what they charge, it's not an unreasonable expectation.
If you send Alpa a lens directly for retrofitting (i.e. not via a dealer) perhaps they take more of an interest, since they don't have to cut the dealer in.
Greygrad's experience sounds poor - the dealer, Alpa and S/K are all being paid to provide a service. For the ~$6.5k (how much?) that it costs to retrofit three lenses, they should all check that the work has been done to the required standard (things are supposed to be simple at the top, right?)
Jim
*This extra QC possibly accounts for why a lens bought new in an Alpa mount is more expensive than buying the same lens new and getting it retrofitted (e.g. R/S 40mm in Alpa SB mount ~US$6.5k; same lens + retrofitting ~US$5.7k).
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Connor Ray
New member
I also bought several large format second hand lenses for 4x5 and 8x10 without any problem at all. The only new lens I ever bought, the SK60Xl have a right to left problem. I was going to buy four tech lenses for my new camera but now I start to wonder...