Exact crop factor of K3 Sensor.


jules

Link Posted 14/02/2014 - 10:00


touché, Brilliant riposte!
Cheers Jules...
tri-elmar-fudd

Back in the room!
“The single most important component of a camera is the twelve inches behind it.”...Ansel Adams
www.exaggeratedperspectives.com

MrB

Link Posted 14/02/2014 - 10:11
Gamka wrote:

jamieallen gave an answer - but with an incorrect calculation which I corrected. That is assuming the sizes of a 35mm frame at 36x24 and APS-C at 23.7x15.7 are exact and for example an APS-Cis not 23.7003x15.7002

But Jules wrote in his first post that the K-3 sensor is 23.5mm x 15.6mm (as shown on the Ricoh web site) so, assuming the same method of calculation, the crop factor would be 1.5339.

Philip

Helpful

Gamka

Link Posted 14/02/2014 - 11:18
MrB wrote:
Gamka wrote:

jamieallen gave an answer - but with an incorrect calculation which I corrected. That is assuming the sizes of a 35mm frame at 36x24 and APS-C at 23.7x15.7 are exact and for example an APS-Cis not 23.7003x15.7002

But Jules wrote in his first post that the K-3 sensor is 23.5mm x 15.6mm (as shown on the Ricoh web site) so, assuming the same method of calculation, the crop factor would be 1.5339.

Philip

And Sony define it as 23.7x15.7 - so who do you believe?

I have also seen it at 23.7x15.6 ...

None of these sets of dimensions is totally accurate - the ration should be exactly 1.504 to match the 6016x4000 pixel count.

tyronet2000

Link Posted 14/02/2014 - 11:30
Smeggypants wrote:
jules wrote:
I'm totally anal!

Lucky for you so are Pentax

http://www.pentaxmedical.ca/en/education/procedure-room-videos.aspx

I was disappointed that the local hospital uses Olympus lenses. I was given some really clear snaps of my innards but can't show them on here
Regards
Stan

PPG

MrB

Link Posted 14/02/2014 - 12:20
The Ricoh/Pentax values of 23.5mm x 15.6mm might well be correct for describing the actual image capture area, if they have been rounded to one decimal place.

Working to 3 decimal places for a hypothetical example, if the dimensions were 23.485mm x 15.615mm, the ratio would be very close to 1.504 - similar to the actual pixel ratio (6016:4000) - and using those hypothetical dimensions would give a crop factor of 1.534.

So the 1.53 Jules has got in his head might be the correct answer!

Cheers.
Philip
Last Edited by MrB on 14/02/2014 - 12:28

Helpful

Gamka

Link Posted 14/02/2014 - 12:27
One way to settle this ... if someone can send me teh sensor from a K3 I will get it measured to within 0.1µm (micrometer)- 100nm or 0.0001mm.

MrB

Link Posted 14/02/2014 - 12:36
Gamka wrote:

... if someone can send me the sensor from a K3 ...

Would anyone want to crop the sensor from their camera?

Philip

jules

Link Posted 14/02/2014 - 12:45
Ok 1.53 it is...
Cheers Jules...
tri-elmar-fudd

Back in the room!
“The single most important component of a camera is the twelve inches behind it.”...Ansel Adams
www.exaggeratedperspectives.com

Algernon

Link Posted 14/02/2014 - 13:31
A Pentax MX is 24mm x 35.9mm

A (cardboard) Kodachrome slide is 23mm x 34mm

So 24x36 is non-existant anyway.

--
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi
Last Edited by Algernon on 14/02/2014 - 13:32

johnriley

Link Posted 14/02/2014 - 13:33
Algi, whatever are you talking about? A Pentax MX is a 35mm film camera with a nominal format of 24x36mm. A Kodachrome slide will no doubt be slightly copped by the mount, but not to 23x24mm!
Best regards, John

johnriley

Link Posted 14/02/2014 - 13:35
Ah, I see you caught up with it!
Best regards, John

sbrads

Link Posted 14/02/2014 - 14:19
We're assuming perfectly square pixels and even spacing between them horizontally and vertically? Assuming things doesn't sit right with me when we're into a few decimal places accuracy. In the real world i.e. taking an actual photo, the aspect ratio will be affected by lens distortion anyway.

Smeggypants

Link Posted 14/02/2014 - 14:40
sbrads wrote:
We're assuming perfectly square pixels and even spacing between them horizontally and vertically? Assuming things doesn't sit right with me when we're into a few decimal places accuracy. In the real world i.e. taking an actual photo, the aspect ratio will be affected by lens distortion anyway.

It'll also be affected by what you view or print the image on.
[i]Bodies: 1x K-5IIs, 2x K-5, Sony TX-5, Nokia 808
Lenses: Pentax DA 10-17mm ED(IF) Fish Eye, Pentax DA 14mm f/2.8, Sigma 17-70mm f/2.8, Pentax-A 28mm f/2.8, Sigma 30mm F1.4 EX DC, Pentax-A 50mm f/1.2, Pentax-A 50mm f/1.4, Pentax-FA 50mm f/1.4, Pentax-A 50mm f/1.7, Pentax DA* 50-135mm f/2.8, Sigma 135-400mm APO DG, and more ..
Flash: AF-540FGZ, Vivitar 283

grahamcoad

Link Posted 22/02/2014 - 17:29
1.5219445275
K-1, Sigma 12-24mm DG EX, Sigma 24-70mm DG EX, K-3, White K-01 with 40mm XS and white 35mm f2.4, SMC Pentax FA 1.8 31mm AL Limited, 43mm f1.9 Limited, 77mm f1.8 Limited, Sigma 17-50 f2.8, SMC Pentax DA* 50-135 f2.8, MX + SMC M 50mm f1.4, SMC A 50mm f1.4, SMC A 50mm f1.2, Spotmatic F 55mm f1.8, ES with 55mm f1.8 and 28mm f3.5, Program Plus (Chrome) with SMC A 50mm f1.7, Pentax 6x7, Leica ii, plus misc. odds and sods)

pentaxk3user

Link Posted 24/10/2019 - 03:40
If you take a photo with a 1 to 1 ratio lens like the Pentax 100mm f/2.8 WR D FA smc Macro Lens and put a mm ruler on a table going up and down and left to right you can see exactly what the dimensions are .
Add a Comment
You must be registered or logged-in to comment.