Autofocus Speeds of Pentax 645Z vs Fujifilm 50S, 50S ii, 100S

[pentaxitin]

Hello everyone.

Can anyone please let me know how good or bad the autofocus speed of Pentax 645Z is compared to Fujifilm 50S, 50S ii and 100S? This is probably the only bit of information I need before making up my mind regarding the second camera I need for aerial photography using a helicopter. 

Thanking you in anticipation. 

[Joe Towner]

The Fuji 50's are just Contrast Detection AF - so slower than the 645z with Phase Detection AF.

The GFX 100 is better than the 645z - partly because of the on chip sensors, but also the lenses are faster & more accurate compared to the screw drive Pentax lenses.

[Remko]

The Fuji 50's are just Contrast Detection AF - so slower than the 645z with Phase Detection AF.

Are you sure that the 645Z has Phase Detection AF? How is this then implemented? This camera has the same sensor as the Fuji 50S (and 50S II) and the latter for sure has no phase detection AF.

cheers,
Remko

[TechTalk]

Are you sure that the 645Z has Phase Detection AF?

You can easily find the answer yourself by simply using Google and searching "Pentax 645Z Autofocus". You can find anything that you'd like to know about the camera specifications and more both quickly and easily with a simple online search.

How is this then implemented?

In the same general manner as in every other SLR camera with phase detection autofocus whether film or digital. Try a Google search for "Phase Detection Autofocus SLR".

This camera has the same sensor as the Fuji 50S (and 50S II) and the latter for sure has no phase detection AF.

The sensor is the same. The cameras are very different.

[Remko]

You can easily find the answer yourself by simply using Google and searching "Pentax 645Z Autofocus". You can find anything that you'd like to know about the camera specifications and more both quickly and easily with a simple online search.

Your comment comes across a bit pedantic .....

Anyway, I googled the official specs of Pentax before posting. And there was noting about Phase Detection AF mentioned.

cheers,
Remko

[TechTalk]

Your comment comes across a bit pedantic .....

Perhaps, but I thought it was more didactic myself.

Anyway, I googled the official specs of Pentax before posting. And there was noting about Phase Detection AF mentioned.

https://www.ricoh-imaging.co.jp/english/products/645z/spec

Autofocus System | Type | TTL: phase-matching autofocus

Anyone interested in a deeper dive into the Pentax 645Z autofocus options and capabilities can find more information below.

https://www.pentaxforums.com/reviews/pentax-645z-review/autofocus.html

[pschefz]

I am assuming that the 645Z has the same PDAF most mirror cameras have, which is not on the sensor but on the mirror. the 50mpix sensor does not have PD AF, the 100 mpix (in the fuji) does.
I have only shot the Pentax once, comparing AF with these cameras is a little pointless IMO, they are all slooooow compared to any modern mirrorless. the fuji 100 is a little faster then the others, fuji probably has the best software so AF might be a little faster then hasselblad and Pentax and probably a little better again with the new 50SII body. but I would not want to shoot a randomly moving child or dog using AF with either one (incl the fuji 100), I do shoot moving people all the time with my hasselblads but I use manual focus.

[Joe Towner]

The 645z/645d as SLR has a af system built in based on the mirror assembly.  The screw drive lenses are pretty quick but can hunt based on the situation - but better than the 50S/R/S II.  The core tech was based on their K camera if I recall correctly.  The screw drive is interesting in that the lenses don't have any electronics in them.  Engage/disengage the AF by push/pull of the focus ring on the lens.

AF is one area not improved with the 50SII body - it's the same chip, without any AF points like the 100/s has.  The 100 will keep up with a kid, better with more light, but keep up none the less.

[TechTalk]

This video is as good as any that I've seen in giving a thorough overview of the various types of autofocusing technologies, how they work, the limitations of each type, and the practical advantages and disadvantages of each type. It goes beyond the basic DSLR phase detection, sensor phase detection, and sensor contrast detection. The newer Sony Hybrid AF, Canon Dual Pixel AF, and Panasonic Depth from Defocus contrast detection are also explored and compared in some detail.

https://www.youtube.com/The Evolution of Autofocus

[BernardLanguillier]

The main problem with 645Z isn’t AF speed, it’s the fact that the AF sensor coverage is tiny and in the middle of the frame.

Not only is it useless in AF-C, it’s also mostly useless in AF-S because of that.

It doesn’t even have a capability to adjust focus after recomposing a la P1 XF/H6D-100c. Btw having owned both of those it works much better on the XF.

The GFX-100s fixes that thanks to it’s full frame AF coverage but… it’s still far behind a mirrorless reference body such as the Nikon Z9. In the end the Nikon will deliver on average far more detailed images on anything that moves, even slowly. I own and use both cameras btw. These days I pretty much only use the Fuji for landscape when the P1 is too heavy or when I expect snow/rain and it’s res is higher than the Nikon.

For the 645Z… I think that a Z7II is just way better for all applications with a level of image quality that’s near identical and simply better lenses. AF is in a totally different class on all types of subjects.

Cheers,
Bernard

[TechTalk]

Important factors in creating an interesting photograph:

Things which are often overrated

• Make, model, or type of equipment used
• Hardware specifications
• Automated features
• Lens resolution
• Speed
• Opinions (including my own) regarding what factors are important for others to consider in evaluating photos and the equipment used to make them

Things which are often underrated

• Photographic skills and craftsmanship acquired over time
• Unique qualities of: subject, viewpoint, technique, image

[BernardLanguillier]

Indeed. And I would add light to the list.

[pentaxitin]

Thanks friends for your comments.

Mostly, what I have found over the last few weeks is that there isn't much advantage to the Fujifilm GFX cameras compared to the Pentax 645Z as far as aerial photography is concerned.

When you need to really nail the exact composition and the focus both in a fast changing scene below, the FF mirrorless cameras are far ahead of any MF cameras, DSLR or mirrorless. I have settled for a Sony A7 iii (may upgrade to A7 iv) with Tamron 35-150 f2-2.8 lens as the primary camera.

When you aren't in a particular hurry and the subject below allows time to compose and shoot in a comparatively less frantic manner, the Pentax 645Z with 28-45 / 45-85/ 55mm lenses is perfectly fine. This camera will remain on hot standby as the secondary camera.