Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-25-2009, 06:32 AM   #1
Veteran Member




Join Date: Nov 2006
Location: Hong Kong
Posts: 1,934
Sensor Size of 645D

Is derived to be 44 x 33mm by me, see my calculations based on existing officially disclosed information so far:-

RiceHigh's Pentax Blog: Sensor Size of the 645D (and More Technical Talks on DSLR Form Factors)

Happy reading!

03-25-2009, 08:02 AM   #2
Veteran Member




Join Date: Mar 2007
Location: Boston, PRofMA
Photos: Albums
Posts: 3,053
Pentax isn't the only MF digital system to crop. AFAIK, the only non-cropped MF digital system is the $40-50K PhaseOne back.
Hassies, Leica, Mamiyas all crop from 1.1 to 1.3...
I put up a table of all the competitors in one of the pentaxforums threads in case you're curious.

I tried to post this to your blog, but it apparently hates Firefox and doesn't work with it :-P
03-25-2009, 09:15 AM   #3
Veteran Member




Join Date: Nov 2006
Location: Hong Kong
Posts: 1,934
Original Poster
QuoteOriginally posted by kenyee Quote
Pentax isn't the only MF digital system to crop. AFAIK, the only non-cropped MF digital system is the $40-50K PhaseOne back.
Hassies, Leica, Mamiyas all crop from 1.1 to 1.3...
I put up a table of all the competitors in one of the pentaxforums threads in case you're curious.

I tried to post this to your blog, but it apparently hates Firefox and doesn't work with it :-P
My Blog is FireFox optimised. Just in case if you've failed to post, I guess its a Google problem.
03-25-2009, 10:43 AM   #4
Veteran Member
Sean Nelson's Avatar

Join Date: Sep 2008
Location: Vancouver BC Canada
Posts: 353
QuoteOriginally posted by RiceHigh Quote
Is derived to be 44 x 33mm by me, see my calculations based on existing officially disclosed information so far:
You've made a fundamental error by assuming that the 75mm lens is normal for a 60 x 45mm "sensor" (ie, film). In fact, the negative size of a film 645 camera is not 60 x 45mm, but rather 56mm x 41.5mm (see: Pentax 645NII Specifications).

...and speculating on the sensor size based on the focal length of a released lens is dubious at best, IMHO. You'll probably get an answer in the right ballpark, but there's certainly no basis to assert that it will be 44 x 33 instead of the more "standard" 48 x 36mm or even something else.

03-25-2009, 06:28 PM   #5
Veteran Member




Join Date: Nov 2006
Location: Hong Kong
Posts: 1,934
Original Poster
QuoteOriginally posted by Sean Nelson Quote
You've made a fundamental error by assuming that the 75mm lens is normal for a 60 x 45mm "sensor" (ie, film). In fact, the negative size of a film 645 camera is not 60 x 45mm, but rather 56mm x 41.5mm (see: Pentax 645NII Specifications).
Then, it has the 120 film cropped, which I have been unaware of.

Anyway, the cropped factor is only 1.076, not a big amount though.

QuoteQuote:
...and speculating on the sensor size based on the focal length of a released lens is dubious at best, IMHO.
That's why I said "based on the officially disclosed information so far".

QuoteQuote:
You'll probably get an answer in the right ballpark, but there's certainly no basis to assert that it will be 44 x 33 instead of the more "standard" 48 x 36mm or even something else.
If it is really still 48 x 36, then this 55mm "standard" lens maybe a bit too wide, i.e., it is of 39mm equivalent of 135 systems for the Angle of View.
03-25-2009, 10:34 PM   #6
Veteran Member
Sean Nelson's Avatar

Join Date: Sep 2008
Location: Vancouver BC Canada
Posts: 353
QuoteOriginally posted by RiceHigh Quote
Then, it has the 120 film cropped, which I have been unaware of.
No camera that takes 120 film actually has a negative that is 60mm across the width of the film. All cameras have to allow a margin for the pre-exposed frame markers and numbers, not to mention the fact that the film gate HAS to be narrower than the film in order to keep it held flat. So it's not really correct to call it "cropped". This Wikepedia article lists the nominal sizes of various 120 film formats.

QuoteQuote:
Anyway, the cropped factor is only 1.076, not a big amount though.
It's in the same order of difference as your resulting sensor size is from the "standard" 48 x 36 size - so it's pretty significant in terms of the results you're suggesting.

QuoteQuote:
If it is really still 48 x 36, then this 55mm "standard" lens maybe a bit too wide, i.e., it is of 39mm equivalent of 135 systems for the Angle of View.
A "standard" lens is a pretty loose thing to begin with. The only vaguely agreed-upon criterion is a lens that has a focal length equivalent to the diagonal of the imaging area. That suggests a field of view equivalent to a 43mm lens on a 35mm film camera. 39mm is closer to that (percentage-wise) than the 50mm lens provided as standard with most 35mm cameras.

The vagueness in the provision of "standard" lenses for cameras is why I think trying to derive the sensor size by looking at the focal length of this new lens is basically a useless exercise.
03-25-2009, 10:45 PM   #7
Senior Member




Join Date: Jun 2008
Location: Atlanta, Georgia
Photos: Gallery
Posts: 182
Not only "it"

QuoteQuote:
Originally posted by RiceHigh
Then, it has the 120 film cropped, which I have been unaware of.
I thought that the actual image size format of about 56x42mm was the standard for 645 cameras, just as 6x6 is about 56x56mm

Photoethnography.com - Classic Cameras

Best regards,
Haakan
03-25-2009, 10:47 PM   #8
Veteran Member
lol101's Avatar

Join Date: Jul 2007
Location: Garennes sur Eure France
Photos: Gallery
Posts: 900
QuoteOriginally posted by RiceHigh Quote
Then, it has the 120 film cropped, which I have been unaware of.
Yes, 6x6 is actually 56mmx56mm, allowing for some space around the pictures.

03-26-2009, 12:04 AM   #9
Veteran Member




Join Date: Nov 2006
Location: Hong Kong
Posts: 1,934
Original Poster
QuoteOriginally posted by Haakan Quote
I thought that the actual image size format of about 56x42mm was the standard for 645 cameras, just as 6x6 is about 56x56mm

Photoethnography.com - Classic Cameras

Best regards,
Haakan
Oh, I see. No MF camera uses the whole frame?
03-26-2009, 04:48 AM   #10
Veteran Member




Join Date: Jun 2008
Location: Borås, Sweden
Photos: Gallery
Posts: 3,165
QuoteOriginally posted by RiceHigh Quote
Oh, I see. No MF camera uses the whole frame?
Pretty much all of them use 56mm of the width (and that is the "frame"), though the film (including the frame numbers etc) is 60-61mm wide. No 35mm cameras use "the whole frame" either if you think about it.

(edit: sorry to disappoint you in that Pentax didn't produce an inferior MF film camera by cropping -- bet that'd make for some good material)
03-26-2009, 05:30 AM   #11
Veteran Member
jeffkrol's Avatar

Join Date: Sep 2006
Location: Wisconsin USA
Photos: Gallery
Posts: 8,435
Are we all playing the guessing game

Kodak Image Sensor Solutions - Full Frame CCD
http://www.kodak.com/global/plugins/acrobat/en/business/ISS/datasheet/fullfr...00LongSpec.pdf
If 31MP then it's probably this sensor.. Why Kodak? US to yen discount....
46.05 X 35....
03-27-2009, 12:20 AM   #12
Veteran Member




Join Date: Nov 2006
Location: Hong Kong
Posts: 1,934
Original Poster
QuoteOriginally posted by pingflood Quote
Pretty much all of them use 56mm of the width (and that is the "frame"), though the film (including the frame numbers etc) is 60-61mm wide. No 35mm cameras use "the whole frame" either if you think about it.

(edit: sorry to disappoint you in that Pentax didn't produce an inferior MF film camera by cropping -- bet that'd make for some good material)
In fact, we can forget well about the actual sensor size, the ratio of the two standard lenses, i.e. 75mm/55mm tells well about the crop factor, which is 1.36X.
03-27-2009, 12:05 PM   #13
Veteran Member
Sean Nelson's Avatar

Join Date: Sep 2008
Location: Vancouver BC Canada
Posts: 353
QuoteOriginally posted by RiceHigh Quote
In fact, we can forget well about the actual sensor size, the ratio of the two standard lenses, i.e. 75mm/55mm tells well about the crop factor, which is 1.36X.
Only if the two lenses have the same field of view (the 75mm on film vs. the 55mm on the 645D).
03-27-2009, 02:42 PM   #14
Veteran Member
Venturi's Avatar

Join Date: Mar 2008
Location: Tulsa, OK
Photos: Gallery
Posts: 2,639
QuoteOriginally posted by RiceHigh Quote
In fact, we can forget well about the actual sensor size, the ratio of the two standard lenses, i.e. 75mm/55mm tells well about the crop factor, which is 1.36X.
QuoteOriginally posted by Sean Nelson Quote
Only if the two lenses have the same field of view (the 75mm on film vs. the 55mm on the 645D).
The 55mm lens being touted as what would ship with the 645D at this point really doesn't tell us squat about the sensor.

But for grins:
75mm on a 645/N/Nii yields an AOV of 50deg and a FOV of 9.33ft (7.47x5.6ft) from 10ft.
In order to make a match you'd need a 41x30.8mm sensor (49.99deg / 9.32ft).
The closest I'm aware of is the Kodak KAF-31600 31.6MP sensor at 44.2x33.1mm and would yield 53.3deg AOV and 10.04ft FOV.
Then again, a 55mm lens on a KAF-39000 or a KAF-50100 (both 49.1x36.8mm) would offer 58.3deg AOV & 11.16ft FOV, which is pretty darn close (theoretically) to the average macular vision of the human eyeball.

So there ya go, depending on what spin to throw at it, a 55mm "kit" lens could mean anywhere from a "new" 41x31mm sensor all the way up to Kodak's 50.1MP beast.
03-27-2009, 03:58 PM   #15
Senior Member




Join Date: Jul 2008
Location: Albuquerque, NM
Posts: 181
MF has traditionally included 46mm square "super slide" format, which fits nicely in a 2X2 slide mount (Carousel projector).


I'm not sure but that may be the same as the Baby Rolleiflex's format.


I personally shot thousands of slide duplicates on long roll 46mm E4 duplicating film using a Forox animation camera. Don't recall the usable film area...might be 41X41. It was a beautiful way to duplicate sections of 35mm slides or, for that matter, 120 or 4X5 sheet film. They were ultimately mounted in Wess anti newton mounts, which are still available.


46mm roll film was also very often used in long roll portrait cameras instead of long roll 70mm ( eg Camerz brand).


This is the same format as Hasselblad's super slide back, which used 120 film and wasted the excess. A super slide film cutting punch was available for that.
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!
645d, camera, medium format, sensor, sensor size, size
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Sensor Size RHN12 Pentax DSLR Discussion 2 09-29-2010 07:14 PM
Sensor size vs. DOF future_retro Photographic Technique 24 09-16-2010 04:30 PM
Sensor size next Pentax K-7 Super RonHendriks1966 Video and Pentax HDSLRs 2 06-21-2010 10:22 AM
What is the optimal size for a camera sensor? asw66 Photographic Technique 24 05-27-2009 10:36 AM
DOF and sensor size simons-photography Photographic Technique 60 04-23-2008 10:55 AM



All times are GMT -7. The time now is 04:20 AM. | See also: NikonForums.com, CanonForums.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