[miro]

[quote name='mst' timestamp='1312893539' post='10552']

Well the simple substraction formular posted above of course contains a small error: normally the manufacturers post the physical length of a lens including mount (to my knowledge at least). Theoretically one would have to substract the depth of the mount from the physical length of the lens.



However, for MFD (or (usually) 1:1) physical length and MFD is all you really need to know to get a good idea about the working distance. The only thing you usually don't know is the depth of the hood, which should be substracted, too. In the field, though, you can simply leave the hood in the bag to increase the effective working distance.



As is written in the text Klaus linked to: calculating the working distance for other reproduction ratios requires knowledge about the lens that is usually not available.



-- Markus

[/quote]



So, it means that WD of OS version is lower than non OS. Since both lenses have the same MFD.

[popo]

[quote name='miro' timestamp='1312905691' post='10555']

So, it means that WD of OS version is lower than non OS. Since both lenses have the same MFD.

[/quote]

Looks that way, although a cm or two I doubt will be a deal breaker.



As for the hood, I've found the Sigma non-OS to be quite flare resistant anyway so even if I'm using it for more distant subjects I don't usually bother with the hood.

[Yakim]

[quote name='popo' timestamp='1312907852' post='10556']

Looks that way, although a cm or two I doubt will be a deal breaker.[/quote]



Indeed, but it's still not a welcomed issue. WD is very important for macro subjects. Couple that with the higher weight and cost and one would need to scratch his head thinking how the pros and cons of the new lens stand against that of the old one.

[popo]

[quote name='Yakim' timestamp='1312921104' post='10559']

Indeed, but it's still not a welcomed issue. WD is very important for macro subjects. Couple that with the higher weight and cost and one would need to scratch his head thinking how the pros and cons of the new lens stand against that of the old one.

[/quote]

Depends on the situation of course. I think the weight difference is not really significant. So would the OS outweigh the WD? I've asked myself that many times debating if I should look at the Canon 100L to supplement the Sigma 150 non-OS. Still haven't come to an answer. On the Sigma 150 non-OS, I do often use it with a 1.4x TC to increase the working distance further, and/or for more magnification.

[Guest]

Hmmm.. I haven't done the math, but during my study at polytechnical colleague we had a shop that could print us layer masks for an 35µm SU-8 process. The colleague did me a favor 4 years ago by ordering 180lpi custom encoder masks for me at that shop which I needed for certain optical position sensors.



What would be the resolution you need, either given in lines perinch oder millimeter line distance?



Christian

[Klaus]

[quote name='TheChris' timestamp='1312957220' post='10564']

Hmmm.. I haven't done the math, but during my study at polytechnical colleague we had a shop that could print us layer masks for an 35µm SU-8 process. The colleague did me a favor 4 years ago by ordering 180lpi custom encoder masks for me at that shop which I needed for certain optical position sensors.



What would be the resolution you need, either given in lines perinch oder millimeter line distance?



Christian

[/quote]





I would need to calculate this in detail but I reckon we would be talking about 20.000 lines per inch or so. White-Black coloring.

[Yakim]

[quote name='popo' timestamp='1312921446' post='10560']

Depends on the situation of course. I think the weight difference is not really significant. So would the OS outweigh the WD? I've asked myself that many times debating if I should look at the Canon 100L to supplement the Sigma 150 non-OS. Still haven't come to an answer. On the Sigma 150 non-OS, I do often use it with a 1.4x TC to increase the working distance further, and/or for more magnification.

[/quote]



Yes, but the price and weight increase and WD decrease also puts it further away from the excellent (and cheap) Tamron 180/3.5. Not an easy decision.



If most of my macro subjects were insects I'd pick the Tamron, as WD would be more important than OS or max aperture. If not, the 100/2.8 IS L looks to be a better all-around lens because it's much smaller and lighter.



As a consumer I applaud Sigma for thinking out of the box and giving us unique lens options but despite its unique capabilities, I think that the target market of the 150/2.8 OS is rather small.

[miro]

[quote name='TheChris' timestamp='1312957220' post='10564']

Hmmm.. I haven't done the math, but during my study at polytechnical colleague we had a shop that could print us layer masks for an 35µm SU-8 process. The colleague did me a favor 4 years ago by ordering 180lpi custom encoder masks for me at that shop which I needed for certain optical position sensors.



What would be the resolution you need, either given in lines perinch oder millimeter line distance?



Christian

[/quote]



The problem with encoder is not resolution. We have novadays rotary encoders with 37 bits/revolution. However the accuracy is still counting in percents % /e.g. 0.01...1%typical value /. When you look at high end encoders from Heindenhain you will come back to Ziess. They use the Zeiss high quality glass for their encoders.

However I woud say that there are not extreme expansive – e.g price of 2000..3000Euro for such encoder or target is still acceptrable???



What will be more exaensive is

1. Keep clean target

2. ALignment of Target

3. Alignment of camera

4. Precisision foucus

5. Environmental disturrbanceses. E.g trilling

======================

I have few ideas. But all of them are very expensive.

If you have some ideas how to solve all 5 issues above please let me/us know.

I'm interested of such setup too

[Christos]

Klaus other than the fact that the EF 100 L IS is 100mm which one is the better lens?

[miro]

Ooops,

The current Imatest target is reflective while encoders base is transluctive.

Target has dark and white areas.The targhet is with high contrast. While most optical encoders are transluctive – metal grid over glas or trans[perant plastic.

Back illuminating is not an option. Since another side effects will occures – scattering, refraction etc. The encoder manufactures do a lot of trics to acheve resonacble sharp images. remember the encoder head is looking for 0 and 1 while we must look for nuaces of light

SinCos encoder is exection of 0s rule, but high end manufacures guaranties 1% THD by perfectly aligned encoder