JensR

Lives in United Kingdom Bath, United Kingdom
Works as a Mechanical Engineer
Joined on Nov 23, 2003
About me:

Hi,

thanks for stopping by!
If you want to see what I'm up to, send me a message :)

My 'plan':
Talk Pentax into a digital Electro-Spotmatic! (This needs some work...)

-------------

Older Signatures:

'LBA knows no bounds, and seeks no justification...' (Jim King, 2005)
http://www.jr-worldwi.de/photo/index.html - Photography, Tech and Geek stuff :}

'Why is everyone answering rhetorical questions?' (Me, 2005)

'Well, 'Zooming with your feet' is usually a stupid thing as zoom rings are designed for hands.' (Me, 2006)

'I only trust those photos I have faked myself.' (Me, 2007)
http://www.jensroesner.de/

--=! Condemning proprietary batteries since 1976 !=--

'I don't want them to believe me, I just want them to think.'
Marshall McLuhan

Comments

Total: 70, showing: 41 – 60
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On article Tamron releases image-stabilized 24-70mm F2.8 zoom (190 comments in total)
In reply to:

Dan: Lens makers, I want something with more range! How come the Fuji X10 can have a 28-112mm F2-2.8 while larger sensor shooters are stuck with lenses like this 24-70 that only zooms less than 3X? Is it because it will be too big? I would LOVE to have a 24-120mm F2.8 with VR. A lot of people liked the 28-105mm F2.8, and with today's technology, I would think that more could be done. With more cameras supporting in-camera lens distortion correction, I'm excited about the future of lenses.

The X10's lens is a 7.1-28.4mm f/2.0-2.8.
If you want to compare that to a lens on "full frame", this can be done, but not by multiplying only one set of those numbers.
The X10's lens is equivalent in angle of view, depth of field control and ability to capture total number of photons per time to a 28-112 f/8.0-11.0 lens on "full frame".

Link | Posted on Feb 6, 2012 at 22:40 UTC
In reply to:

gordonpritchard: If I remember correctly, it is possible to change the effective aperture on a catadioptric lens by making an off center hole in a lens cap and placing that in front of the lens.

Yes, this works - Sigma (IIRC) even had a two-piece lens-cap for that purpose. I have used cardboard cut-outs. I have tried with centred holes, though. It was mildly successful to increase exposure time and DOF, but did not really cure optical aberrations like stopping down usually would.

Link | Posted on Feb 3, 2012 at 18:48 UTC
In reply to:

Bart Hickman: 300mm/F6.3 on micro 4/3 = 600mm/F12.6 on full frame or 400mm/F8.4 on APS-C. Doesn't sound so amazing to me.

Of course you have to multiply the f-stop as well, as the f-stop is a measurement including the focal length and the aperture diameter. The same aperture diameter (and equivalent f-stop) lets through the same number of photons per time and creates the same DOF.
So Bart is correct.

Link | Posted on Feb 3, 2012 at 18:46 UTC

That's interesting, I think.
Live view focusing will mean that the relatively shallow DOF is less of an issue. Maybe it will even take normal front-mounted filters?
The small size will make its use off a tripod easier than the 800/8 available for "FF", even without a dedicated tripod mount.

Link | Posted on Feb 3, 2012 at 18:43 UTC as 33rd comment

Sorry, I mad a mistake.
No more selective colouring for me, either.

Link | Posted on Jan 26, 2012 at 02:46 UTC as 119th comment
In reply to:

fenceSitter: F2.8 on an m43 camera doesn't sound like "large aperture" to me, as far as Bokeh is concerned. If I'm not mistaken, it will be the same as with a F5.6 lens on a Nikon D700.

No, Jacques, this was not an excellent summary by Zvonimir.

The distinction between "total light" captured (number of photons) and "light density" (photons per area) is crucial with sensors of different size, even if you dislike it. Along with that it is important to know the distinction between aperture diameter (in mm) and f/number (a dimensionless measure).

You also need to consider that a lens for the smaller sensor needs to be sharper in linepairs/millimetre to give the same resolution of linepairs/image (the really decisive measure). It is not a "desire" as Zvonimir puts it - the higher lp/mm of 4/3 glass is a necessity.

Link | Posted on Jan 13, 2012 at 21:48 UTC
In reply to:

Claudio Pinchi: I really don't understand all these complaints about DOF of M43. I recently bought a GH2 and (among others) the Leica Summilux 25 f1,4 and I can honestly say that DOF and bokeh are absolutely first quality, also compared to the same lens on my 5D (Canon ef 50 f1,4). Seems that many people ignore that DOF is influenced not only from aperture but also distance from subject. I will not buy these new lenses probably... but honestly who can say a 24-70 f2,8 is not an interesting lens? Kit lens in m43 is really poor in quality. People that look for more image quality (at the expense of portability) will surely buy this zoom. What make IMHO m43 still a little lower step to DSLR is the small choice of high level lens. If I look to the shots of my GH2 compared with ones took with DSLR with APS sensor and standard lens... i can say... NO GAME! The small m43 lens make more simple to reach high optical quality.

P.S: i beg your pardon for my poor english ;-)

Nikkor:
There are no _equivalent_ 4/3 lenses to a 24-70/2.8 - this would be a 12-35/1.4.
Otherwise, I agree, horses for courses, just make sure to compare properly.

Vlad:
Equivalence is not pedantry. It accurately predicts the behaviour of lenses regarding light transmission, angle of view and DOF. These are crucial ingredients to a photo and calling this pedantry is wrong.
If you find DOF too shallow, that is your right, but you are in no position to decide for anyone but yourself.

bbb:
The lens does not change. That is correct. But you know how people talk about that a 12mm lens on FT behaves like a 24mm lens behaves on FF? Okay, the same physical formula needs to be applied to the f/#. The same formula can also be used to say how one and the same lens behaves if attached to different sensor sizes (assuming it covers that sensor size).

Larry: Your corrected post is #umm# correct!

Link | Posted on Jan 13, 2012 at 21:42 UTC
In reply to:

fenceSitter: F2.8 on an m43 camera doesn't sound like "large aperture" to me, as far as Bokeh is concerned. If I'm not mistaken, it will be the same as with a F5.6 lens on a Nikon D700.

Comparing to FF is not odd or flawed.
If the prices stay as announced, the FT f/2.8 lens is more expensive than a "FF" f/4.0 (or f/5.6) lens that has better (or the same) DOF control due to the larger (or same) physical aperture diameter.
Just because primes generally offer more DOF control does not invalidate that people also want DOF control from their zooms - or else we would all run around with f/11+ zooms...

Link | Posted on Jan 11, 2012 at 23:47 UTC
In reply to:

Jens_G: Meh. That 12-35/2.8 is basically equivalent to the Nex kit lens. It has the same physical aperture as a f/3.5 on APS.

Actually, the physical aperture (=diameter) of 12/2.8 on FT and 16/3.6 on APS-C are the same. The F-number is different, though (obviously).

Link | Posted on Jan 11, 2012 at 23:42 UTC
In reply to:

Claudio Pinchi: I really don't understand all these complaints about DOF of M43. I recently bought a GH2 and (among others) the Leica Summilux 25 f1,4 and I can honestly say that DOF and bokeh are absolutely first quality, also compared to the same lens on my 5D (Canon ef 50 f1,4). Seems that many people ignore that DOF is influenced not only from aperture but also distance from subject. I will not buy these new lenses probably... but honestly who can say a 24-70 f2,8 is not an interesting lens? Kit lens in m43 is really poor in quality. People that look for more image quality (at the expense of portability) will surely buy this zoom. What make IMHO m43 still a little lower step to DSLR is the small choice of high level lens. If I look to the shots of my GH2 compared with ones took with DSLR with APS sensor and standard lens... i can say... NO GAME! The small m43 lens make more simple to reach high optical quality.

P.S: i beg your pardon for my poor english ;-)

This is not a 24-70/2.8 lens. This is a 12-35/2.8 lens, that behaves like a 24-70/5.6 would on "FF".

And of course position influences DOF, but for a correct comparison you need to maintain the position and hence perspective - otherwise you are not comparing the same things.

Link | Posted on Jan 11, 2012 at 23:39 UTC
In reply to:

Sabatia: This is exactly one of the directions Pana needs to go to have a fuller system. If the lenses are as fast as 2.8, sharp, and with high color resolution, that would be almost perfect. Having sold all my Canon gear this fall, the two lenses I miss most are the 17-55 EFS 2.8 and the 70-200 f4 L, which between them probably took 75% of my favorite shots over the last dozen years. I suspect that I am not alone in terms of 30/40/50/7D shooters in loving these lenses. So Yeah! Now get them done, glitch-free, and into the stores. And if the 35-100 is f4, but smaller and lighter than the Canon f4, I will be still be very happy.

Canon's comparable lenses at 2.8 cost $1,000 and over $2,000 or $1,400 for the 70-200 f4 IS. I think if Pana can get these out at $1k to $1,200 they will be winners.

PS: While the aperture size on m4/3 will cause loss of a little depth of field compared to crop cameras and more to FF, the brightness is not similarly affected.

12/2.8 on fourthirds is equivalent to 24/5.6 on "FF": Same DOF, same number of photons per second.

Link | Posted on Jan 11, 2012 at 23:37 UTC
On article Lightroom 4 Review (469 comments in total)

Wow, RGB curves, finally! Highlight recovery with (seemingly) much less colour skewing! Geotagging with track import! I might have to abandon XP after all this time.
PS: Good review, thanks.

Link | Posted on Jan 10, 2012 at 20:59 UTC as 168th comment
On article Digital lo-fi photography - Part 1 (131 comments in total)
In reply to:

jjmiphoto: This is too much iOS love, you left out Paper Camera, an awesome Android app that makes lots of awesome looking images.

Hi Simon,
JJ and odoketa pointed out the very strong focus on iOS. JJ merely suggested one Android app.
I think a more specific reply from dpreview could have explained why you looked at 10 iOS apps and 1 Android app - surely you had a good reason for that imbalance. Is it market share? I don't know, I don't have a "smart"phone. Maybe titling this "an overview of lo-fi iPhone apps" would have created fewer false hopes.

Link | Posted on Dec 12, 2011 at 21:50 UTC
On article SLR Magic announces 23mm F1.7 for Sony NEX's E-mount (60 comments in total)
In reply to:

tkbslc: "The world's fastest interchangeable camera lens with APS-C coverage in this focal length"

Pretty easy when you use a non-standard focal length like 23mm! :) However, there are multiple 24mm f1.4 lenses out there. I'd almost suspect it is really a 24mm that they labeled as 23mm for marketing purposes.

Francis, you might want to check the Rodenstock first, before getting all haha:
http://www.graham-mitchell.com/blog/?p=43
That monster is an ultrawide lens for the 645 format and could probably sink an iceberg.

Link | Posted on Dec 12, 2011 at 18:15 UTC
On article Ricoh to make 16MP APS-C GXR zoom module (136 comments in total)
In reply to:

Magnus W: The GXR is such a great concept! A camera with a swappable camera. Wonder why no one thought of this before.

Some people have a broken sarcasm detector.

Link | Posted on Nov 29, 2011 at 21:14 UTC
In reply to:

obeythebeagle: Looks suspiciously like the classic Leitz 50mm M-series Summicron.

No, the "standard" cropped 645 format does not let in more light and DOF is not more shallow than "FF". Uncropped 645 comes close to FF, but is much more expensive, much more bulky and much slower. If shallow DOF and capturing as many photons as possible per time is what you are interested in, then nothing beats FF in bang for the buck.
This is not due to physics, but due to the available lenses for 645 - that's why FF wins out.

I'm lucky in that I have several cameras with different sensor formats, so I can pick the most suited system to whatever I do.

Link | Posted on Nov 11, 2011 at 20:41 UTC
In reply to:

obeythebeagle: Looks suspiciously like the classic Leitz 50mm M-series Summicron.

A 24/2.8 on the D700 is easily available and lets in more photons per second for the same angle of view. This equates to more shallow DOF, too. Minimum focus distance of Nikon's 24/2.8 is worse, at 12".
However, the Sigma 24/1.8 comes to mind - but that will be a bit larger. Given the ease of operation of the AF/AE lens on the D700 compared to the all manual "SLR Magic" lens, this might be the better compromise.

Link | Posted on Nov 10, 2011 at 20:13 UTC
On article Lytro announces Light Field Camera (269 comments in total)
In reply to:

deletedGregR1: ok, so in that physical size and with a constant f/2, the lens is obviously a really wide-angle piece. and with a wide angle, even at f/2, nearly everything is in focus anyways. just look at their sample pics - HUGE depth of field, especially evident in the golfer pic. i wouldn't be surprised if they cheaped out and simply shot an image at f/8 and then "defocus" in software. hmm, i smell something only slightly more legit than a scam.

Greg: it is "280mm equivalent" but not "f/2 equivalent" - simply f/2.
If we go with the front element of 35mm diameter and f/2, we get a focal length of 70mm. Meaning a crop factor of 4 to reach "280mm equivalent". The 70/2 lens will thus behave like a 280/8 on FF would. Not too bad. I do however think that this overestimates the sensor size. If you look at zoom lenses ending at about 300mm equivalent, you will notice that they are actually slower than focal length divided by front element diameter. The crop factor will therefore probably be larger than 4.

Link | Posted on Oct 19, 2011 at 22:03 UTC
On article Just Posted: Samsung NX200 hands-on preview (129 comments in total)

Mistake in preview:
In the "Compared to the Samsung NX100" the small product shots are identical for NX100 and NX200.

Link | Posted on Sep 1, 2011 at 15:06 UTC as 21st comment

> for all intensive purposes

This should be "for/to all intents and purposes".
http://wiki.answers.com/Q/Is_the_saying_%27all_intents_and_purposes%27_or_%27all_intense_purposes%27

Also, the link at the top is to the proper test of waterproof cameras but the text says "Click here to read our group test of travel zoom compact cameras" - which probably was carried over from a previous test.

Link | Posted on Aug 17, 2011 at 15:57 UTC as 26th comment | 1 reply
Total: 70, showing: 41 – 60
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