Lens Trial: Sk 50mm F 2.8 - Coin Community Forum

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Author	Replies: 5 / Views: 2,174
austrokiwi Pillar of the Community 2087 Posts	Posted 01/22/2015 11:21 am Heres the full title Lens trial: Schneider Kreznach componon S 2.8/50mm Makro Iris. I have no idea if any one is interested in this: but I have found nothing on the web about using such lenses for macro photography: I did some research into the modern macro lens Schneider Kreznach currently produce. In the process I got a n offer to try before you buy of a used example of the 50mm. The lens has become mine. 50mm wouldn't be my first choice. I wouldn't even normally look at any of the SK macro lenses they start at US$500 and top out at over US$1000. The 50mm retails at around US$600.00 The one I have (second hand) is costing me equivalent to US$200 plus a painful €75.00 for the V mount to T2 adapter. Heres what the lens looks like: the vmount is a V shaped channel the adapter has three hex drive grub screws that lock into that chanel. the lens aperture is infinitely variable from 2.8 to 16. After finding it is sharpest at F8(4 on the lens scale) I have locked it down at that aperture: using the three grub screws used for the purpose. Its a machine macro lens designed to set and forget. You can reverse it by removing the front cover: Here it is with all the adpaters mounted: Mounted on my Bellows( minus camera): ( Sorry phot0bucket isn't cooperating a doesn't what to rotate the photo) With all the adapter on it and mounted the native magnification is low(€10.00 note) Look at the yellow star to the right of the zero of 10: at full bellows extension this is the result( the star is 7.5mm high my sensor is 24mm high = 3.1-1 magnification?) The Microprinted letters are not more than 0.3mm high. I can't see them with my bifocals without a magnifying glass: this is what the SK can do: It was shots like the one above that made me decide the lens was a keeper. In comparison heres the maximum magnification of a minolta MC 50mm macro( the manual says it can go higher...but how you can get light on the subject is problematic!) And the money shot for me( well really the shop that has sold me the lens): 100 % crops side by side the SK crop is obvious by its clarity( remember the letters are around 0.3mm high) The other shot that sold me this lens is this one: Actually I wasn't impressed looking through the EVF...It was only when I saw the picture on the computer that I realised the lens was out resolving the EVF( I must check to see that the EVF is adjusted right!) I tried the lens resersed. Maximum magnification on my set up was not much of an increase( heading towards 4-1 magnification( probably 3.5-1) 100 % crop from the above image: Edited by austrokiwi 01/22/2015 11:32 am Report this Post to the Staff

rmpsrpms Pillar of the Community United States 4036 Posts	Posted 01/22/2015 9:51 pm Nice lens there. Expensive adapter! But it was purpose-made by SK so makes a good set. 50mm are good for medium mags on bellows. What is the minimum mag you can get on your bellows? I haven't tried too many 50mm since I don't think I can capture a whole cent on any of my bellows. Most of the lenses I've linked to over the years have been 75mm or longer because of this. But if you're doing higher mags 50mm is a great length since the working distance is favorable. How well does it do wide open? 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 01/22/2015 11:33 pm The minimum magnification is about 1-0.1. The native magnification of the lens is very low. Its designed for use with extension tubes SK asks a lot for those( think US$200 -$300) So a bellows is the only way to go. The lens was designed to produce optimal results at 1-2 through 1-1 magnification. I wouldn't normally go for a 50mm either. I really would love to try the 90mm APO version but at US$1200 that isn't going to happen. I kept the lens for one reason( apart from being a new toy): I had been looking at getting one of the available micro lenses Olympus 38 & 20 MM,the minolta 24 & 12mm or the canon counterpart. This SK 50mm performs the way I expect one of those micro lenses does, and was a little cheaper) I think its a lens that really compliments the Stack shot, for full coin pictures it is only useful for smaller coins. I can get a silver dollar sized coin using a 13mm extension ring but I have other lenses that do that job. Its the resolving power at moderate magnification (above 1-1)that this lens excels at. It gives an undistorted field of view in comparison to a microscope objective. At maximum extension the lens to subject distance was a little more than the width of a Jansco light head The adapter is an absolute ripoff all it is is a short(6.5 mm) tube with an internal diameter of 37mm with an M42(T2 pitch) male thread at one end. A workshop could probably turn out four for the same cost that SK adapter sells one for.(SK don't retail, the supplier of the adapter was Edmunds optical) I will have to check its performance wide open.....from memory it was little different to at F8 ( as far as resolution goes.....depth of field is, of course the issue. Edited by austrokiwi 01/22/2015 11:59 pm Report this Post to the Staff
aladinslamp Pillar of the Community United States 3076 Posts	Posted 01/23/2015 01:57 am is there a fact or something, you refer to that the print was 3 mils high, so the depth of field is the true nature of the lenses characteristics?, I realize that the depth of field, interferes with they type of shot your trying to get an actual "in focus" shot across the photo, as coins are not a flat object depth of field is a very important aspect for any lens. Report this Post to the Staff
austrokiwi Pillar of the Community 2087 Posts	Posted 01/23/2015 04:04 am Aladinslamp. Not sure that I fully understand. The micro printing in the picture was what I referred to meaning the letters were only 3mls in size....it was only to give an idea of how much resolution the lens was producing. Depth of field is 90 degrees in the other direction and as always the depth of field is very shallow. Its just enough for a small flattish coin. the one I showed is only 16mm in diameter. This lens is one that can be used for a single shot but My main use of it will be with stacking...and from what I have seen so far it will excel at that. My problem has been I can get 5X - 10X shots Ok but there has been a hole in the 3-4X region. Often I want to illustrate a feature requiring a larger field of view than what a microscope objective will produce. This 50mm produces edge to edge sharpness that is distortion free and with high resolution 3X magnification. its performing exactly as it is designed to do. The lens projects a 43mm image circle so its brilliant on a full frame sensor. On the weekend I will set my camera to APS-c mode and post a test shot. Edit here is a stacked shot( 4X magnification) I could have got away with less than the 10 shots I took to produce this. To get the 4X I had to add some extension rings to the bellows, even then the lens was far enough away from the coin that a couple of janscos( the lights I love to hate) could do their job. Edited by austrokiwi 01/23/2015 05:44 am Report this Post to the Staff
austrokiwi Pillar of the Community 2087 Posts	Posted 01/23/2015 3:58 pm Final test shot: As I said I would I set the camera to ApSc capture mode: the following shot is straight out of the camera( no editing) and into Photobucket. Lens was mounted directly to the camera( magnification is 1:41 Calculated from the known coin size and the size of APSc I starting to think that 90mm might be worth it!! Report this Post to the Staff
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