Jan Madsen

Jan Madsen

Lives in Denmark Borup, Denmark
Works as a Software development
Joined on Sep 20, 2006

Comments

Total: 7, showing: 1 – 7
On Nikon AF-S Nikkor 58mm f/1.4G review preview (402 comments in total)
In reply to:

Scottelly: I wish they would just update the 50mm f1.2 AIS lens into an auto-focus G lens with nano-crystal coatings (to slightly improve the image quality) with the EXACT SAME optics in all other respects. That would be AWESOME. Of course, maybe they already considered that, and they decided not to mess with a good thing (they already have the 50mm f1.2 AIS, and it works great). This lens certainly gives people more choice, doesn't it?

Scottelly you need to view the rear pupil with the eye approximately where the sensor is - everything else doesn't make sense - photos of the rear pupil are from far away, and will show wildly varying sizes. Put your eye close to the rear of the lens, and the f/1.2 pupil will look nearly the same both for a 50mm and a 85mm. And yes, the Canon EF mount is substantially larger, so that f/1.2 is easy, and f/1 is just possible. Furthermore, the smaller Nikon F mount is further from the sensor (enough space for a Nikon->Canon converter ring), making things even worse.

Direct link | Posted on Jan 5, 2014 at 21:59 UTC
On Nikon AF-S Nikkor 58mm f/1.4G review preview (402 comments in total)
In reply to:

Scottelly: I wish they would just update the 50mm f1.2 AIS lens into an auto-focus G lens with nano-crystal coatings (to slightly improve the image quality) with the EXACT SAME optics in all other respects. That would be AWESOME. Of course, maybe they already considered that, and they decided not to mess with a good thing (they already have the 50mm f1.2 AIS, and it works great). This lens certainly gives people more choice, doesn't it?

To Scottely: You must distinguish between front pupil and rear pupil. The front pupil is detemined by focal length divided by aperture, so a 200mm f2 lens is 100mm (big!). Rear pupil is almost 100% dependent on aperture, not focal length. So a 200mm f2 and a 24mm f2 have rear pupils about the same size, and thus require about the same amount of mount diameter. All this is a simplification, but it is an easy way of describing things. So as aperture, not focal length, is the important parameter at the rear, there is a limit on how large an aperture can be handled by a particular mount, irrespective of focal length - limited by the mount diameter in conjunction to its distance from the sensor. Most mounts are limited to around f1.2, inlcluding the Nikon mount, but Nikons electrical contacts gets into the way for f1.2, unless you cheat by letting them cover a little of the rear lens. Canon does the same for f1.0, the contacts sits on a platform over the edge of the rear lens.

Direct link | Posted on Dec 31, 2013 at 11:17 UTC
In reply to:

HiRez: Wow, that is one bigass 55mm lens. Why can't they make an autofocus version of their lenses though?

In reply to Petka: There is no technical obstruction for making the lens autofocus. The Canon 85mm f/1.2 moves the complete optical system (except the rearmost element) during (auto)focusing, and that is one heavy clump of glass, much heavier than a 55mm f/1.4. Same with the Canon 50mm f/1, also a heavy lens with lots of glass.

Zeiss has decided to omit AF, that is a marketing decision. Makes the system technically much simpler, and they avoid all the hazzle of reverse engineering the AF protocol/interface for each camera brand.

Direct link | Posted on Aug 8, 2013 at 11:49 UTC
On Sigma launches APO Macro 180mm F2.8 EX DG OS HSM news story (129 comments in total)
In reply to:

dansclic: High quality at moderate prices ???? I Am dead !!!! If you want quality you have to pay for, cheap stuff from sigma is not a good deal : 50 per cent is decentered, mecanical problems, un reliable autofocus.....
So again a 1700 USD Lens and what ? Buy a used nikon or canon instead.

Sigma lenses so far (for Canon 1DsII and 5DII):
15mm f/2.8 fisheye: Fine.
12-24mm f/4.5-5.6: Fine.
20mm f/1.8: Required tape on the hood to avoid ratteling.
28mm f/1.8: Fine.
70mm f/2.8 macro: Sharpest lens ever encountered.
100-300 f/4: Fine.
So except for the tape on the 20mm hood (just like the Canon 200mm f/1.8!) no problems at all for 6 lenses.

Direct link | Posted on Jul 13, 2012 at 08:39 UTC
On Canon EOS 5D Mark III preview (923 comments in total)
In reply to:

Adler1970: I explain to you what kind of digital DSRL revolution was created by Nikon, with the D800:

Until now, the lenses were superior to the sensor. The sensor had to run behind the lenses. And these lenses were out of breath. But now, WIHT NIKON D800, the lenses are running out of breath behind the sensor. Now, the sensor is more advanced than any lens. This is a revolution, this is the uterus of a new generation of LENS, of a new generations of fotos, of a new vision, of a new GRAPHICS, of new corporate identity and corporate design.

That is BIG words, when the linear resolution increase from 5D3 to D800 is only 28%. I can assure you that lots of lenses will easily outresolve the D800 in the center. Not withstanding that the Nikon D800 is an impressive camera (I hope Canon makes something similar soon) I find it ridiculous to belive that going from 22 to 36 MP suddenly steps over a magic border which no lenses can cross...

Direct link | Posted on Apr 6, 2012 at 14:54 UTC
On CES 2012: Sigma stand report article (25 comments in total)

Not the worlds first 180mm f2.8 macro - Sigma made one earlier, in the 1990's, also with AF. So it is kind of a revival.

Direct link | Posted on Jan 14, 2012 at 01:39 UTC as 3rd comment
In reply to:

J.K.T.: I simply can't figure out what is the point of having both this and 150/2.8 OS.

Just like what's the point of having both a 24 and a 28mm in the catalog. Choice. I have the Sigma 70mm macro, the 150mm would complement it nicely, someone having a 100-105mm might find the 180mm a good second longer macro.

Not the first time Sigma had a 180mm f2.8 macro though, so it's kind of revival, with all the modern additions of course.

Direct link | Posted on Jan 10, 2012 at 10:09 UTC
Total: 7, showing: 1 – 7