Schneider Kreuznach Xenon-E(Emerald) 50mm F2.2 - Page 2

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Author	Replies: 21 / Views: 5,998	Page: of 2

andywoj00 Valued Member United States 441 Posts	Posted 06/08/2016 6:59 pm So are you basically showing on the first two shots that this particular lens cannot be focused properly at these apertures? What exactly is being conveyed info-wise with your eval of this lens as compared to the SK? Report this Post to the Staff
rmpsrpms Pillar of the Community United States 4038 Posts	Posted 06/08/2016 11:57 pm Hard to tell if f3.5 is the optimum aperture for the 40mm at 5x, but if so then it's operating at NA 0.11. If it needs to be stopped-down further it's NA is even smaller. So likely a 4x or 5x NA 0.1 objective can do as well or better on small sensors. Large sensors are a different story. Contact me for photographic equipment or visit my home page at: http://macrocoins.com Report this Post to the Staff
austrokiwi Pillar of the Community 2087 Posts	Posted 06/09/2016 12:42 am Quote: So are you basically showing on the first two shots that this particular lens cannot be focused properly at these apertures? What exactly is being conveyed info-wise with your eval of this lens as compared to the SK? What I am showing is the SK50.2.2 is a bad lens for our purposes. rmpsrmps had noted it just kept on getting sharper as he closed down the aperture, which is a bad sign. Believe it or not those first two soft shots were in focus( as much as that lens could do on the full frame sensor it was amazing to see the transition when I changed the aperture to F4 from F 3.5. The subject suddenly became sharp. Now my point on using the lenses reversed is a general comment. Good Microscope objectives are expensive US$200-US$800 ( and much higher) and for the use I get out of them just a basic 50mm F 2.8 mm lens reversed gives me all I need, a magnification range of up to 5X. I had long ago thought about getting the canon MPE 65mm macro ( because it covers that magnification range) but, in the end I realized it was just collectors avarice. I was just not going to use a lens like the MPE 65 enough to warrant the expense. I could go and buy a good 14th century Florin or Ducat for the price. For my purposes a reversed enlarger lens( or even a reversed wide angle 21-24mm range) would suffice. On the full frame I didn't take the 40mm beyond 3.5 because in the past I had found there was only slight improvement and the effects of diffraction cut in pretty quickly after 3.5. Report this Post to the Staff
rmpsrpms Pillar of the Community United States 4038 Posts	Posted 06/09/2016 11:15 am To further AK's point, a more general-purpose lens is very useful in many imaging applications. My typical application is 3D image rendering, and in this work the highest quality objectives with thinnest DOF are required for vertical resolution. On the other end of the spectrum, if only a single image is desired for documenting varieties and such, then a much lower quality objective/lens is acceptable, because to get enough DOF for a single image to be sufficient the lens must be heavily stopped-down. Between these extremes, where vertical resolution is not needed for 3D, but the user is willing to do focus stacking, there is a wide range of acceptability. Even the 50/2.2 can operate in this range, but at lower quality than AK's 40/2.8. With these lenses the user has control over the DOF, and thus the number of images required for the stack. The user can even stop-down these general-purpose lenses to give wide DOF so stacking is not necessary, of course with lower resolution. Contact me for photographic equipment or visit my home page at: http://macrocoins.com Report this Post to the Staff
pepactonius Pillar of the Community United States 9395 Posts	Posted 06/09/2016 3:55 pm Quote: Where exactly does that comment come from? It looks like you have to stop this lens down from f/2.2 to f/4, before it gets sharp, so a 4x / .20 microscope objective ought to give better sharpness, at least near the center. The advantages of the 50/2.2 would be better working distance, and when reversed, it might cover a medium format sensor. One advantage of the 4x / .20 is that it doesn't attach via a flimsy and vibration-prone bellows, but rather by a rigid metal tube, containing the tube lens (edited to fix problem with disappearing dots in ".20") Edited by pepactonius 06/09/2016 3:58 pm Report this Post to the Staff
rmpsrpms Pillar of the Community United States 4038 Posts	Posted 06/09/2016 8:16 pm I've never noticed any vibration in my system due to any of several brands and models of bellows. A 4x/0.20 objective is a rare and expensive beast, and of course will do better than any other optic at 4x for center sharpness. I have one, but very rarely use it since it lacks coverage even for APS-C. I find that a 4x/0.13 gives sufficient vertical resolution for 3D rendering. A lowly 4x/0.1 is generally good enough for most coin photography purposes, having narrow enough DOF to require several images in the stack. Contact me for photographic equipment or visit my home page at: http://macrocoins.com Report this Post to the Staff
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