Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
08-06-2013, 03:40 AM   #226
Loyal Site Supporter




Join Date: Mar 2009
Location: Southern Indiana
Photos: Gallery
Posts: 14,955
QuoteOriginally posted by jsherman999 Quote
You don't always need it - but to have it available is very nice at times.



.


Can your 'pragmatism' magically bring more light to the scene? Fast lenses add to your system's power and capability, they are not something you graduate from when you (or your sensor) get 'better'.

.
Is dynamic range related to sensor size, or is it related to sensor type? When I look at the K5 versus the D800, the D800 has a little more dynamic range, but not a whole lot. But maybe that has to do with iso 80 being available on K5 and not on the D800.

08-06-2013, 08:29 AM   #227
Pentaxian
Digitalis's Avatar

Join Date: Mar 2009
Location: Adelaide.
Posts: 8,535
QuoteOriginally posted by falconeye Quote
OTOH, it is F/1.4, an unheard of aperture for MF. So, it probably is a mix of both worlds
Well not really, what I suspect Zeiss has done is merely changed the rear cell of the lens so then the lens can sit closer to the sensor. The flange for the Hasselblad V series lenses are designed for is 74.9mm and if you optically alter the rear focusing group of the lens so that infinity focus is possible at 44.00 mm flange** which is almost half the flange focal distance intended for the lens, and by doing this there will be higher luminous intensity at the imaging plane. It also explains why this 55mm f/1.4 T* lens is so massive compared to its counterparts - 35mm cameras are only using the central 43mm of the 89mm imaging circle that this lens is capable of projecting. The vignetting figures from this lens confirm this - as most Zeiss 35mm SLR lenses and rangefinder lenses typically have rather large amounts of vignetting - and this lens doesn't have this issue even at f/1.4 - theory fits evidence. The only way to empirically confirm this is to get one and put it on a Alpa FPS with a MFDB.



**Canon EOS flange

Last edited by Digitalis; 08-06-2013 at 08:45 AM.
08-06-2013, 10:45 AM   #228
Pentaxian




Join Date: Dec 2011
Posts: 1,154
[[deleted]

Last edited by beholder3; 08-11-2013 at 07:40 AM. Reason: [deleted]
08-06-2013, 07:00 PM   #229
Pentaxian
jsherman999's Avatar

Join Date: Dec 2007
Photos: Gallery
Posts: 8,228
QuoteOriginally posted by Rondec Quote
Is dynamic range related to sensor size, or is it related to sensor type? When I look at the K5 versus the D800, the D800 has a little more dynamic range, but not a whole lot. But maybe that has to do with iso 80 being available on K5 and not on the D800.
As the ISO goes up, the larger sensors have typically gained the advantage in DR.

I think Falk has a handle on the specifics of DR with regard to it's relationship to pixel QE and sensor size, he'd probably be the best to answer. I do have Bill Claff's data available - his formulation of PDR (Photographic Dynamic Range) usually tracks DXOMark's numbers pretty closely iirc... Below is PDR for the D7000 (K-5 sensor,) D700 and D800 at various ISOs:




From This Link

08-06-2013, 11:05 PM   #230
Pentaxian
Digitalis's Avatar

Join Date: Mar 2009
Location: Adelaide.
Posts: 8,535
QuoteOriginally posted by beholder3 Quote
Even though I do not see how sheer proximity would change luminosity in a large scale, you are pretty much describing the process of building a lens specific "speedbooster"
The increase is actually bigger than you think - if you have ever used macro extension tubes with your lenses you would be aware of how much of an impact in terms of light loss is experienced when increasing the distance between the exit pupil of a lens from the imaging plane.What I described is almost the same as a speedbooster but not exactly - because a large amount of the lenses imaging circle isn't being used.
08-07-2013, 02:32 AM   #231
Pentaxian
falconeye's Avatar

Join Date: Jan 2008
Location: Munich, Alps, Germany
Photos: Gallery
Posts: 6,862
QuoteOriginally posted by jsherman999 Quote
I think Falk has a handle on the specifics of DR
Assuming a CONSTANT pixel architecture (size and technology), then base ISO, read-out noise per pixel and the full well capacity of a pixel remain constant too. DR is then proportional to #pixels, read sensor surface. I.e., log2 of it if measured in stops, i.e. doubling the surface adds 1 stop in DR. One can show that this remains true if only the pixel technology is a constant, pixel size is irrelevant.

Another way to view it is by describing the APSC camera in 35mm-equivalent terms: E.g., the K-5 has an *equivalent* base ISO of 190. The reason the D800 isn't twice the DR of the K-5 has to do with the mythical ISO 80 Pentax anaged to get from the Sony sensor...

It is possible though to design a sensor with *equivalent* base ISO of e.g. 100: it would be a true ISO 40 sensor. To achieve it, you have to make the silicon thicker such that the full well capacity is about doubled. It is the TOTAL number of electrons a chip can store which counts. And if you don't make the chip wider, you can still make it thicker. But as it increases the chip cost, making it wider may make more sense because it yields a FF chip easier to sell. I rather see a true ISO 50 FF sensor to go into those $5000+ bodies ...
08-07-2013, 03:45 AM - 1 Like   #232
Pentaxian
falconeye's Avatar

Join Date: Jan 2008
Location: Munich, Alps, Germany
Photos: Gallery
Posts: 6,862
QuoteOriginally posted by Digitalis Quote
... which is almost half the flange focal distance intended for the lens, and by doing this there will be higher luminous intensity at the imaging plane. ...
QuoteOriginally posted by Digitalis Quote
... it is a distagon design ... much like the Zeiss CFI 50mm f/4 Distagon for the hasselblad V
I fear this can't be as easy

First, a lens diameter is foremost f/N (this is why aperture is written as it is, after all ...). So, 55mm/1.4=39mm and 50mm/4=13mm. Shortening the flange distance plays no role in this, except for lenses which are retrofocus designs.

Second, the Distagon 50/4 for Hasselblad is a more complex design than the Planar 50/1.4. It has 9 elements rather than the Planar's 7. But it is still a relatively small and simple lens. The image circle does not normally have a large impact as long as it remains smaller than the focal length or in a strict telecentric design.

The speedbooster comment was off-topic as it changes a lens' focal length too.

Distagon is just one out of a few type designation which Zeis is using. It does NOT mean that a design was reused or is reusable. The others are e.g., Planar, Tessar, Sonnar, Biogon. Although their generic designs are all Zeiss patents, they are widely used by all others w/o using the patent names. Distagon just means retrofocus design.

The Distagon 55/1.4 for 35mm is an entirely new design. The only thing it has in common with the Hasselblad lens is that it is a retrofocus design. It has 12 elements and its main challenge was to correct corners at F/1.4. An industries' first.

The retrofocus design is not necessary for a 55mm on a 35mm body. They used it because it allows for a more uniform performance across the image field which was a design goal.

Optically, it must resemble the Sigma 35/1.4 Art (which is a 13 elements F/1.4 Distagon design too) more than anything else. But of course, the lens elements must have more than twice the surface (55/35)^2 which gives a much bigger and more expensive lens.

See Zeiss' Dr. Nasse talk about it here (youtube video 8mEj6CqZWMk ):
(at 2:30 min)
08-07-2013, 05:37 AM   #233
Veteran Member
Nesster's Avatar

Join Date: Oct 2006
Location: NJ USA
Photos: Gallery
Posts: 13,047
QuoteOriginally posted by jsherman999 Quote
As the ISO goes up, the larger sensors have typically gained the advantage in DR.

I think Falk has a handle on the specifics of DR with regard to it's relationship to pixel QE and sensor size, he'd probably be the best to answer. I do have Bill Claff's data available - his formulation of PDR (Photographic Dynamic Range) usually tracks DXOMark's numbers pretty closely iirc... Below is PDR for the D7000 (K-5 sensor,) D700 and D800 at various ISOs:




From This Link
That chart is precisely the chart of NEW DIGITAL TECHNOLOGY PROMISE vs ACTUAL EMOTIONAL AND PHOTOGRAPHIC RESULTS when TAKING FULL COST INTO ACCOUNT.

My mini review of the K-30: nice camera, gave it to daughter to use. Haven't read the manual so I don't know what all it will do. Tried shooting with it, the clouds haven't parted.
My mini review of the D600: nice camera, gave it to daughter to use. Trying to read the manual so we can figure out how to use the damn thing. Tried shooting with it, the clouds definitely did not part.
My mini review of a 1915 No.1 Autographic Kodak Special: Loads of fun, the lens amazed, the results are encouraging, though there are scratches on the film and some light leaks.
My mini review of a 1898 Cooke lens on a '40s RB Graflex 2x3: Lots of fun getting it to work, nice results. The skies parted.
My mini review of a Pentax MX: whoa, the D600 calls itself a full frame camera? Not if you look in the view finder. Ok so I can't adjust ISO from shot to shot from 100 to 100,000,000,000,000, and the AF sucks, the AE sucks, and it lacks nearly every mode and feature that sells cameras these days. Nice camera after Eric did his thing, I gave it to my nephew for his 21st birthday. Missed it, so bought another from KEH in their EX condition.

Now, I'm not a total troglodyte and Luddite when it comes to modern cameras. Both are much nicer to use than the old K100D, and although I don't have direct experience as yet, I can imagine both will have better focusing than my daughter's K-x. On the other hand, I tote up the total spend, less any future sale proceeds, and I can fairly predict the overall cost is far more than with the rest of my film camera menagerie put together. Mind you, the K100D is at a point where I'm not sure it is worth selling, the K-x still is...

08-07-2013, 09:00 AM   #234
Veteran Member
Nesster's Avatar

Join Date: Oct 2006
Location: NJ USA
Photos: Gallery
Posts: 13,047
... .... and while I'm 'reviewing' the D600: I don't mind yellow and black, I don't even mind it saying Nikon on it, but why do they feel the need to advertise the model number on the damn strap??? Is that for the typical ego-compensating Nikon buyer (which I appear to be one of)? Pentax has this one right, and classy. I put on a vintage red and black strap with clips so I can remove it, and now the Nikon is tolerable to take out of the house. I might even put a Pentax strap on it.

I bought it factory "reconditioned". S-jeah, sure. The copyright value is still set to the prior owner (Hi!) and sure enough, there are sensor blobs in frame 1 of the camera. In other words, Nikon did nick name for richard except cosmetically. But I don't mind the sensor, I've been cleaning them for years. The copyright is cool, though I could not figure out how to change it.

The vaunted Nikon three dee distance and color savvy matrix metering seems to over expose, especially flowers, where Pentax doesn't. Oh, and what's with the default auto pop up flash? (again, I'll need to dive in the manual to make that one work the Pentax way)...

24 MP is vast.










All taken with the "embarrassing" AF-D 28/2.8 Nikkor.
08-07-2013, 09:11 AM   #235
Pentaxian




Join Date: Jun 2009
Location: GMT +10
Photos: Albums
Posts: 10,589
Hey Nesster, Pentax could do a 24MP FF with little effort, I think. Keep your Pentax glass.

I just wonder about what Pentax have planned to make their FF special, in some way, beyond the similarly specced D600 and 6D. What could make it distinctive (aside from the K-mount) over those two competitors...
08-07-2013, 09:13 AM   #236
Site Supporter
Cynog Ap Brychan's Avatar

Join Date: Sep 2012
Location: Gloucester
Photos: Gallery
Posts: 1,090
QuoteOriginally posted by rawr Quote
What could make it distinctive (aside from the K-mount) over those two competitors...
120 colours?
08-07-2013, 09:40 AM   #237
Veteran Member
Nesster's Avatar

Join Date: Oct 2006
Location: NJ USA
Photos: Gallery
Posts: 13,047
QuoteOriginally posted by Cynog Ap Brychan Quote
120 colours?
Well, as they already have a crop 120 camera, why not a 120 color film full 6x4.5 camera with a 35mm digital back?
08-07-2013, 09:41 AM   #238
Veteran Member
Nesster's Avatar

Join Date: Oct 2006
Location: NJ USA
Photos: Gallery
Posts: 13,047
QuoteOriginally posted by rawr Quote
Hey Nesster, Pentax could do a 24MP FF with little effort, I think. Keep your Pentax glass.

I just wonder about what Pentax have planned to make their FF special, in some way, beyond the similarly specced D600 and 6D. What could make it distinctive (aside from the K-mount) over those two competitors...
But they haven't and unless I sell the Nikon I won't be looking for a long while. The only Pentax I'm thinking of getting rid of is the K-x.

For the distinctive bit, they can find a novel way to create a QC issue.
08-07-2013, 03:22 PM   #239
Pentaxian
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 8,937
QuoteOriginally posted by falconeye Quote
See Zeiss' Dr. Nasse talk about it here...
Thanks for sharing this.

Fascinating performance by the lens and very interesting to see and hear Dr. Nasse.
I've read articles by him and it nice being able to put a face to a name.
08-07-2013, 05:56 PM   #240
Pentaxian
Digitalis's Avatar

Join Date: Mar 2009
Location: Adelaide.
Posts: 8,535
QuoteOriginally posted by falconeye Quote
I fear this can't be as easy
If it was easy Zeiss would not have bothered making the 55mm f/1.4 T*. Bear in mind my comments are of a theoretical nature, I just figure it would be easier for Zeiss to use an existing Distagon lens design than come up with an entirely new one - but considering the history of Zeiss, they could have come up with a new design without difficulty.

The only way to empirically confirm whether this lens is an altered MEdium format lens is to simply use it on an ALPA FPS equipped with a MFDB with a 35mm lens adapter.

Last edited by Digitalis; 08-07-2013 at 06:02 PM.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
24x36mm, aps-c, benefit, depth, ff, field, filter, frame, frame pentax, fuji, full-frame, goldilocks, iq, iso, noise, pentax, picture, resolution, sensor, terms
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
So.... Pentax Full Frame is a sure thing? LFLee Photographic Industry and Professionals 25 11-02-2012 12:55 PM
Why is the K7 so terrible? or rather why am i having such a problem with it? runslikeapenguin Pentax DSLR Discussion 60 05-01-2012 01:16 PM
Why do people want a Full Frame sensor? RobG Pentax DSLR Discussion 98 02-15-2012 09:12 AM
Is there such a thing as a decent superzoom (for Pentax)? DanielT74 Pentax SLR Lens Discussion 22 06-21-2011 05:57 AM
Full-Frame Image Sensor Holy Grail - Why? stewart_photo Pentax DSLR Discussion 82 10-10-2007 03:00 AM



All times are GMT -7. The time now is 05:34 AM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top