[biz-engineer]

For many photos, it wouldn't make any visible difference.

In general (flat images), you wouldn't see a significant difference between apsc and ff formats, ok.
For the case of the 70-200 and 50-135, that's completely untrue: both lenses are primarily designed and used for portraits because of the focal length range, distance to subject and convenience and changing the field of view (include or exclude more or less of the background to frame the environment of the subject). For other applications such as air shows, sports and animals, 50-135 is mostly too short, 60-250 , 200mm or 300mm are preferred. Back to portraiture, between the 70-200 2.8 on FF and the 50-135 2.8, the difference in image rendering / bokeh is as visible as the increase in weight and price, due to the size of the diaphragm opening is twice as large on the 70-200 vs 50-135. Shooting 170mm f2.8 on FF delivers similar bokeh as 85 f1.4@f1.4, about 113mm @f1.8.

Going the 70-200 + FF route make sense if you need to deal with the noise, mostly.

Not at all. While you can use a 70-200 f2.8 on a K3 to get in the 100-300 range for sports, the use of 70-200 on FF has nothing to do with noise.

---------- Post added 16-05-16 at 22:13 ----------

And my bet is even with all the difference between K3 + FA77 & F135 on one side and K1 + 70-200 on the other side,

The F135 is meant to be used on FF, this is for the same use of 90mm on K3: head the shoulders portraits.

[Nicolas06]

In general (flat images), you wouldn't see a significant difference between apsc and ff formats, ok.
For the case of the 70-200 and 50-135, that's completely untrue: both lenses are primarily designed and used for portraits because of the focal length range, distance to subject and convenience and changing the field of view (include or exclude more or less of the background to frame the environment of the subject). For other applications such as air shows, sports and animals, 50-135 is mostly too short, 60-250 , 200mm or 300mm are preferred. Back to portraiture, between the 70-200 2.8 on FF and the 50-135 2.8, the difference in image rendering / bokeh is as visible as the increase in weight and price, due to the size of the diaphragm opening is twice as large on the 70-200 vs 50-135. Shooting 170mm f2.8 on FF delivers similar bokeh as 85 f1.4@f1.4, about 113mm @f1.8.

Not at all. While you can use a 70-200 f2.8 on a K3 to get in the 100-300 range for sports, the use of 70-200 on FF has nothing to do with noise.

The point for me was 50-135 f/2.8 on APSC vs 70-200 f/2.8 on FF. You get same field of view, lighter pack on APSC. You get a bit less shallow dof, bit worse AF performance and bit more noise. End of story.

What is more important to you dictate the choice between the 2 solutions. If anyway a 70-200 on FF is too short for sports/airshow and wildlife (I have my doubt for some action/sport fields), it performance for action/sport is so irrelevant.

As f/2.8 not separating the subject enough that subjective...

FA77 f/4



F135 f/2.8... Here anyway the hand/glass would be OOF otherwise. Not necessarily the best:



F135 f/2.8... Indoor, wall just behind. Lamp near the subject (if you look well). The background is completely abstracted.



FA77 f/3.5, outdoor




This is not the f/2.8 limitation on APSC that will destroy you picture but you capability (or not) to frame correctly, take the right moment etc.

[biz-engineer]

This is not the f/2.8 limitation on APSC that will destroy you picture but you capability (or not) to frame correctly, take the right moment etc.

Yes, apsc at f2.8 completely destroyed my pictures! Open your mind, and as much as you studied DXO parameters, study this method here: https://en.wikipedia.org/wiki/Brenizer_Method
That's why I need a 2Kg lens and a 1kg camera hunk, then I can do what noonelse can do with a iphone, MFT or APSC.

Regarding the OP, I don't feel that the Pentax full frame system (including DFA70-200) is more monstruous that the large format view camera that the French photographer Raymond Depardon is using to do his artistic photography works.

[Nicolas06]

Yes, apsc at f2.8 completely destroyed my pictures! Open your mind, and as much as you studied DXO parameters, study this method here: https://en.wikipedia.org/wiki/Brenizer_Method
That's why I need a 2Kg lens and a 1kg camera hunk, then I can do what noonelse can do with a iphone, MFT or APSC.

Regarding the OP, I don't feel that the Pentax full frame system (including DFA70-200) is more monstruous that the large format view camera that the French photographer Raymond Depardon is using to do his artistic photography works.

I know brenitzer method thanks... Funilly people do that with a FF, a 85mm f/1.4 and will spend hours in PP... Not sure that's a major use case. But if it is a priority for you or somebody else, I have nothing against it.

I still think for many other people the compromize of weight/size/price is not that interresting... In the grand schemes of things, people that are great photographer take great photo, almost regardless of the gear they have.

If you want to study, take a look at these video serie... How greats photographer take great picture with terrible camera:

You Tube

You Tube

Look for example what lara jade managed with a 0.3MP baby toy camera... There are example of picture taken with it at the end of the video...

[biz-engineer]

I still think for many other people the compromise of weight/size/price is not that interesting...

That's correct from your standpoint because you compare the Pentax apsc offering (limited primes) to the new Pentax FF system. If you were coming from Canon or Nikon, you wouldn't be surprised as much. For the money , the K3 + limited lenses are really good.