JensR

JensR

Lives in United Kingdom Bath, United Kingdom
Works as a Mechanical Engineer
Has a website at http://www.jr-worldwi.de
Joined on Nov 23, 2003
About me:

Hi,

thanks for stopping by!
If you want to contact me, just visit my homepage.
http://www.jr-worldwi.de
I am happy about feedback and mails!

My 'plan':
a) Get a D7 to work in IR as well as my modded Olympus 2040IR :->
(This is partly done, but there's a new project going on...)
b) Talk Pentax into a digital Electro-Spotmatic!
(This still needs some work...)

I am currently shooting with:
Pentax *ist DS
Pentax *ist DSIR
Pentax MZ-5n
and a few lenses.
These cameras give me great possibilities.

Former cameras
Olympus 2040IR / Minolta D7IR(modded for IR work)
Revueflex 5005 (not as often)
And:
Olympus 4040 (not for long)
Minolta D7 (not for long)
Olympus 2020
-------------

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: 66, showing: 21 – 40
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On Compositional Rules article (120 comments in total)

The rule of thirds is just a simple way to do a rough golden ratio, with the benefit of being able to map the whole frame in one go, whereas golden ratio will give different intersections, depending on which side you start from.

Direct link | Posted on Aug 21, 2012 at 23:08 UTC as 30th comment
In reply to:

EasyClick: Correct me if I'm wrong, but isnt NASA supposed to have technology decades ahead of what's available on the market? They're the guys inventing the science and breakthrough technology...By the same reasoning they should have a photo sensor that would only be available today on the market. I understand the article but I just thought otherwise... Maybe someone should send an iPhone to Mars??

This is the real world, not Hollywood.
An iphone would not make it past the moon before radiation kills it.

Direct link | Posted on Aug 15, 2012 at 15:46 UTC
In reply to:

Scott Eaton: I'm not by any means a NASA engineer, but I am an Engineer on the IT side of things. I realize we're working with extreme data management constraints and 2004 technology curves.

My issue is why we're using a bayer based sensor when we want the most discrete data to come from our hardware. Why waste data pathing with all that interpolated nonsese just because somebody is more familiar with Kodak. We're taking pictures of other worlds, not snaphots of your kids.

Here's to hoping Kodak is out of business so they are forced to use better hardware the next time around.

I guess using three 0.7MP sensors, one for each colour would be better than using one 2MP sensor, but the alignment problems during the rough entry of the spacecraft might have been problematic.
I hope you were not suggesting a Foveon chip as a way to discrete data :)

Direct link | Posted on Aug 15, 2012 at 15:45 UTC
On Evolution of an image article (123 comments in total)
In reply to:

The Schillings: Really nice shot. I find the image a little too HDR-ish. I think the foreground is too bright, and there are no distinctive shadows so maybe up the blacks.

No Bossa, it is clear to see that the foreground shadow brightness was increased a lot, robbing it of natural depth. And yes, it is a 3-shot HDR image, as stated underneath each picture.

Direct link | Posted on Aug 10, 2012 at 12:54 UTC
On Evolution of an image article (123 comments in total)
In reply to:

JensR: ISO 400, f22, from a tripod.
Why?

Danke Carsten! But f/22 seems a bit extreme. Why did you not use tilt? At f/22 you are losing resolution and extending the exposure time needlessly, introducing extra noise because of the increased ISO. f/11 and a slight tilt at ISO 100 seems like the better option?

Emmanuel - the question was not just why Carsten used a tripod. The exposure-merging alone would explain that. The question was primarily why Carsten went for ISO 400 despite using a tripod.

Mark: While we are at it, might we want to ask the f/64 group about the Scheimpflug effect and camera movements?

Direct link | Posted on Aug 10, 2012 at 00:22 UTC
On Evolution of an image article (123 comments in total)

ISO 400, f22, from a tripod.
Why?

Direct link | Posted on Aug 9, 2012 at 18:09 UTC as 60th comment | 9 replies
In reply to:

Heather Protz: Seems quite big.

> Come on, it's a 150mm f/1.8 lens.

It is not a 150/1.8 lens. It is a 75/1.8 lens.
It has the same FOV, DOF and captures the same number of photons per time as a 150/3.6 lens would on "full frame".

Direct link | Posted on May 24, 2012 at 17:34 UTC
On Pentax K-01 studio test shots published article (146 comments in total)
In reply to:

duartix: WTF?
Did I just see a 1EV advantage over the all mighty K-5? in RAW???
Pinch me!!!

*punch*
Sorry, must have misread your request ;)

Direct link | Posted on May 3, 2012 at 02:05 UTC
On Canon acknowledges 'light leak' in the EOS 5D Mark III article (257 comments in total)
In reply to:

IcyVeins: LOL CANON'S FINISHED NOW! GOODBYE TO THE OLD DINOSAUR! LONG LIVE SONY!

I detect a sarcasm leak here.

Direct link | Posted on Apr 16, 2012 at 22:19 UTC
In reply to:

RCicala: OK, let me condense this:
We are establishing a monopoly in order to serve you better.

Right.

Osam, how do you get from "repairing broken parts" to "sharing an operating system"?

Direct link | Posted on Mar 13, 2012 at 22:22 UTC
On Just posted: Our Samsung NX200 in-depth review article (175 comments in total)
In reply to:

Wenger: You made a mistake in the lens selection, the 16mm is F/2.4 not F/2.8.

I'm pretty sure that they did mean full-time manual focus. This type of motor allows full time manual override of the autofocus.

Direct link | Posted on Feb 28, 2012 at 23:22 UTC
In reply to:

bradleyg5: Yawn, wake me up with they hit F/0.8. f0.95 is not terribly impressive when you only have to produce an image circle 1/4th the size of fullframe. sure the intensity of light is high, but the total amount of light passed through the lens is not worthy of that price tag.

> Cropping, however, doesn't reduce DOF

So very very wrong.

Direct link | Posted on Feb 8, 2012 at 19:21 UTC
On Tamron releases image-stabilized 24-70mm F2.8 zoom article (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 light densities (photons per area and time) of all f/2 lenses are the same - but I never said anything else.
But an f/2 lens on "full frame" will cover roughly twice the area than f/2 on APS-C with that same photon density, so it captures twice the number of photons per picture and unit of time.

Hence, your 400/2.8 and 14/2.8 example is just not what we are discussing. As they both project onto the same sensor, they of course project the same number of photons per time and image _as_well_as_ same number of photons per area and time.

Your reasoning that focal length is the only thing different is incomplete. It is quite clear that the aperture diameter (in mm) is different as well. Which brings us back to my original point.

Direct link | Posted on Feb 7, 2012 at 19:52 UTC
On Tamron releases image-stabilized 24-70mm F2.8 zoom article (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.

No, it's completely true - everything I said. I said "number of photons" - not "density of photons".
It's simple physics, but I have realised by now that people are very reluctant to accept it. They will rather believe that they get a "28-112 f/2.0-2.8" lens. Strange though that their "28/2" shots do look nothing like a real 28/2 looks on "full frame". Wonder why that is... ...well, if you understand what I said in my first post, you won't need to wonder any more.

Generally, I would not buy an F8 to F11 zoom lens - which was exactly my point. Such a lens can be very compact, though - so it's not as "idiotic" as you might think.

Direct link | Posted on Feb 7, 2012 at 00:01 UTC
On Tamron releases image-stabilized 24-70mm F2.8 zoom article (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".

Direct 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.

Direct 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.

Direct 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.

Direct 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.

Direct 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.

Direct link | Posted on Jan 13, 2012 at 21:48 UTC
Total: 66, showing: 21 – 40
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