[2351HD]

The 645D, whilst an excellent camera by all accounts, is quite old by now - sensor technology has come a long way since it was released. DXO shows the 645D's maximum dynamic range to be 12.6 EV, versus the APS-C sensor K-3's 13.4 EV... and as the ISO rises from base, the 645D's dynamic range will undoubtedly suffer quicker than the K-3. The K-1 will perform even better than the K-3, so...

I would likely take the 645d DR over that of the K3. The 645d holds up really really well when being worked heavily and I doubt the K3 would keep up in PS.

[BigMackCam]

I would likely take the 645d DR over that of the K3. The 645d holds up really really well when being worked heavily and I doubt the K3 would keep up in PS.

I don't understand that last sentence, given that the K3 actually has greater dynamic range than the 645D (according to DXOMark, that is). Plus, by ISO 1600 the 645D's sensor performance is losing steam, while the K3 continues to be very useful at this point, and indeed easily up to ISO 6400 (I frequently shoot at ISO 6400 and above). Now, your 645Z on the other hand... that, I would obviously take over the K3 for DR...

[BenCPentax]

ISO range isn't the same as dynamic range, is it.
Top dslr's can shoot in very low light stopped down and get a decent picture,
but take a photo on a tripod at iso 100 and compare the tonal range of the different sensor sizes.

[BigMackCam]

ISO range isn't the same as dynamic range, is it.

No, it certainly isn't. Dynamic range is the same as dynamic range, though, and the dynamic range of the 645D at any measured ISO is lower than the K3. Of course, that's just one measurement, and there are other aspects of the larger sensor that are beneficial. Tonal range, as you mentioned, is about equal at all ISOs for the 645D and K3, with just the *tiniest* advantage to the 645D. SNR is a bit better for the 645D too - not hugely, but enough that I would probably go with the 645D in the right situation...

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Last edited by BigMackCam; 03-22-2016 at 05:30 AM.

[BenCPentax]

Think I got confused by tonal gradation of film sizes between 35mm and 6x9 :-)
Why didn't they make the viewfinder on the new 645 bigger ? The specs seem a bit poxy.

[BigMackCam]

Think I got confused by tonal gradation of film sizes between 35mm and 6x9 :-)
Why didn't they make the viewfinder on the new 645 bigger ? The specs seem a bit poxy.

I can't speak from experience, but the review on this forum states:

The size of the 645Z's viewfinder image is huge compared to that of an APS-C or even a 35mm full frame DSLR such as a current Nikon FX body. The LCD data panel is also unusually large and therefore easy to read. The big viewfinder makes manual focusing less of a hit or miss than with smaller formats. The viewfinder covers 98% of the frame, which close enough in our opinion in most cases. If 100% accuracy or high magnification is required, then live view is the way to go. The lack of live view in the 645D was one of our key complaints, so we are thrilled to see that the 645Z addresses this issue.

Sounds pretty good to me, but then I'm more than happy with viewfinder in my K3 & K3II, so anything more is gravy...

[Winder]

People need to stop thinking about ISO the same way they think about film.

The ISO 12232:2006 standard

The ISO standard 12232:2006[15] gives digital still camera manufacturers a choice of five different techniques for determining the exposure index rating at each sensitivity setting provided by a particular camera model. Three of the techniques in ISO 12232:2006 are carried over from the 1998 version of the standard, while two new techniques allowing for measurement of JPEG output files are introduced from CIPA DC-004.[16] Depending on the technique selected, the exposure index rating can depend on the sensor sensitivity, the sensor noise, and the appearance of the resulting image. The standard specifies the measurement of light sensitivity of the entire digital camera system and not of individual components such as digital sensors, although Kodak has reported[17] using a variation to characterize the sensitivity of two of their sensors in 2001.

The Recommended Exposure Index (REI) technique, new in the 2006 version of the standard, allows the manufacturer to specify a camera model’s EI choices arbitrarily . The choices are based solely on the manufacturer’s opinion of what EI values produce well-exposed sRGB images at the various sensor sensitivity settings. This is the only technique available under the standard for output formats that are not in the sRGB color space. This is also the only technique available under the standard when multi-zone metering (also called pattern metering) is used.

The Standard Output Specification (SOS) technique , also new in the 2006 version of the standard, effectively specifies that the average level in the sRGB image must be 18% gray plus or minus 1/3 stop when exposed per the EI with no exposure compensation . Because the output level is measured in the sRGB output from the camera, it is only applicable to sRGB images—typically JPEG—and not to output files in raw image format. It is not applicable when multi-zone metering is used.

The CIPA DC-004 standard requires that Japanese manufacturers of digital still cameras use either the REI or SOS techniques. Consequently, the three EI techniques carried over from ISO 12232:1998 are not widely used in recent camera models (approximately 2007 and later) . As those earlier techniques did not allow for measurement from images produced with lossy compression, they cannot be used at all on cameras that produce images only in JPEG format.

The saturation-based technique is closely related to the SOS technique, with the sRGB output level being measured at 100% white rather than 18% gray. The saturation-based value is effectively 0.704 times the SOS value .[18] Because the output level is measured in the sRGB output from the camera, it is only applicable to sRGB images—typically TIFF—and not to output files in raw image format. It is not applicable when multi-zone metering is used.

[BenCPentax]

-Trapezoid prism finder
-98% coverage
-0.62x magnification (with 55mm lens)
--3.5 to +2 diopter adj.


-Pentaprism
-100% coverage
-0.95x magnification
--2.5 to +1.5 diopter a

645 & K3

Looks like the new 645 has quite small viewfinder magnification with a wide lens.
Viewfinder design being about trade offs, 100 % view with big magnification and massive eye relief
would be ideal but not possible.

[BigMackCam]

Looks like the new 645 has quite small viewfinder magnification with a wide lens.
Viewfinder design being about trade offs, 100 % view with big magnification and massive eye relief
would be ideal but not possible.

Bingo.

[GeneV]

These full frame threads make me long for the calm of the old days of the political forum.

[jsherman999]

These full frame threads make me long for the calm of the old days of the political forum.

Bring it back I sez!

[rawr]

The ISO standard 12232:2006[15] gives digital still camera manufacturers a choice of five different techniques for determining the exposure index rating at each sensitivity setting provided by a particular camera model.

And to add to the confusion, DxOMark do ISO testing their own way too:

ISO sensitivity measurement protocol - DxOMark

[Parallax]

These full frame threads make me long for the calm of the old days of the political forum.