However, this reminds me of the fact that the 645D, like all other K-mount Pentax DSLRs, is actually also cropped for its sensor. So, I just wonder, how is the 645D different from those 135 FF DSLRs and how "large" is the difference? And besides, what are the trade-offs?
Here we go, for the factual data:-
| Camera | Sensor (Film) Type | Sensor (Film) Size (in mm x mm) | Diagonal Length (in mm) | Crop Factor A | Crop Factor B | Crop Factor C |
|---|---|---|---|---|---|---|
| 645 Film | 120 | 56 x 41.5 | 69.7 | 1X * | 0.79X | 0.62X |
| 645D | Cropped 120 | 44 x 33 | 55 | 1.27X | 1X * | 0.79X |
| D800/E | 135 | 36 x 24 | 43.3 | 1.61X | 1.27X | 1X * |
| K-5II/s | APS-C (Cropped 135) | 23.7 x 15.7 | 28.4 | 2.45X | 1.94X | 1.52X |
Is everything much clearer now? The myth has been resolved!
In fact, the 645D is the "APS-H" of the original 120 film with a crop factor of nearly 1.3X. The same applies when the 135 FF is compared to the 645D, which has the exact crop factor in 1.27X. So, how much advantage does it give?
And, *suppose* that there is a Full Frame 645D which exists, the 135 FF will then become a 1.6X "Canon APS-C" cropped machine in comparison, then this difference would be more significant!
On the other hand, the truly APS-C sized K-5IIs for its sensor, when compared to the 645D, is really sympathetic! It is almost in 2X, just like when the micro-4/3 sensors are compared to the 135 FF. Actually, the APS-C sensor is much smaller than the 135 FF, its total area of the sensor is just only in 43%!
Well, what are also in return with that cropped sensor in the old 645 form factor for the 645D then? A big, heavy, slow but rather expensive camera, but which is actually NOT having a significantly larger sensor, and thus no big edge in IQ as a result!
Indeed, cropping an old sensor/mount format is always stupid in the digital era, unless new lenses with a smaller image circle which fits more tightly into that smaller image sensor are re-designed and made!
This is the end of case and the case is closed! The 645D now is a meaningless offer after all! If Pentax is listening, please give us Full Frame DSLR bodies soonest, no matter for the K or 645 mounts!! >:-(
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Snappertim · 622 weeks ago
Regards Snappertim
Guest · 622 weeks ago
I think that the problem is not in imaging circle but with lens resolutions and CAs.
It is much easier to fit lens resolution and controll CAs with the not so dense sensor (bigger but with same resolution). But again if your sensor stays more dense the problem grows. You will never be happy as it is much easier to create good dense sensor than new lens which fits it. And especially whole portofolio of lenses...
andrew munster · 622 weeks ago
VoiceOfReason · 622 weeks ago
Andrew Munster · 622 weeks ago
Andrew Munster · 622 weeks ago
error fixed
Andrew Munster · 622 weeks ago
Yoku · 622 weeks ago
1. No any 56*41.5 mm sensor now.
2. The manufacturer is not bound to produce only 56*41.5 mm sensors, because there is no any practical sense.
3. That's why 40 MP with sensor 44*33 mm is the mainstream MF digital sensor now.
There is big space for sensor size and for MP, but it's not called-for product now. 80 MP sensors with 1.05x crop-factor are rare and marginal bird with huge price.
mario · 622 weeks ago
Yoss · 622 weeks ago
Anonimity is Great · 622 weeks ago
I agree with your statement regarding image circle. It is somewhat pointless to have bigger than you need image circle for any given sensor. It is, however, *not* pointless to enable your (very) old lenses to be mounted with your new DSLR. It is interesting, it is fun. It is one of many pentax USPs, and one that has brought many photographers, me included, to Pentax. It is not a stupid decision. It is correct.
Furthermore, at the beginning of digital era, DSLRs cost a lot of money, even when they are using APS-C sensors. The decision to use cropped sensor (definitely a cost cutting measure) on FF mount or Lenses was to ease us into taking up photography. And based on how many people now owns these APS-C DSLRs, it is not a stupid decision. It is correct.
Sure many now wants FF sensored DC, and Pentax haven't delivered yet on that front, and you can complain all you want about that fact, but the decision Pentax, and Canon, and Nikon, and Sony, and Samsung, and Fuji, have made to release APS-C DSLR using their old *FF* mounts, is definitely *not* stupid!
You owe them an apology.
David · 622 weeks ago
What about 645 sensor size - 44x33mm is a normal DIGITAL sensor, so called digital 4x5cm film frame. Hasselblad is the same. Phase One sensors also are NOT true 4x5cm size (36x48). I guess you know it. But... hey, this blog is about Pentax (or how bad Pentax is).
Dan Johnson · 622 weeks ago
anonymous · 622 weeks ago