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12-25-2019, 12:17 AM   #13966
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Re post by kaseki about image stabilization...


Wouldn't IBIS do the job adequately? It already works wonders on the other Pentax cameras.

12-25-2019, 03:43 AM   #13967
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QuoteOriginally posted by TDvN57 Quote
Re post by kaseki about image stabilization...


Wouldn't IBIS do the job adequately? It already works wonders on the other Pentax cameras.
I have wondered why SR cannot be built right into the medium format cameras just as with the K mount cameras. It is such a desirable feature that I have to imagine there is some major reason why not. I have no idea whether there are either engineering or economic barriers to doing so. Maybe Adam can opine on this.
12-25-2019, 09:37 AM - 1 Like   #13968
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QuoteOriginally posted by ivanvernon Quote
I have wondered why SR cannot be built right into the medium format cameras just as with the K mount cameras. It is such a desirable feature that I have to imagine there is some major reason why not. I have no idea whether there are either engineering or economic barriers to doing so. Maybe Adam can opine on this.

There are some non-obvious factors involved due to lens magnification. The effect of the lens on the image at the focal plane is a transformation of angle to displacement. When the photographer moves the angle of the camera-lens assembly, a point in the image moves on the focal plane. How much it moves depends on the magnification and, in the case of roll, on the distance from the optical axis of the correction servos. Hence, correcting the focal plane by moving it requires measuring the angular motion (rate sensor integration is probably good enough for this) and then calculating focal plane motion to correct it. At the other end of the optics, angular motion can be corrected 1:1 if performed ahead of the lens objective (or 1:2 if certain configurations of mirror stabilization systems are involved).

Nonetheless, building MS into the camera body allows motion to be corrected independently of the lenses, so long as focal length is known. This requires less material, complexity, and cost than making every lens MS. However, the Z, D, N, etc. do not already have MS in the body, so we have to live with whatever is available. To MS the huge number of FA lenses used with the present Pentax MF camera bodies calls for an external stabilizer, or a much lower cost but inconvenient in some cases tripod.

What might be possible, if camera space exists, would be for an affordable upgrade to the 645Z. I suspect that it could only be affordable if a relatively large fraction of the 645Z ownership population were on-board with the idea.
12-25-2019, 09:55 AM   #13969
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QuoteOriginally posted by kaseki Quote
There are some non-obvious factors involved due to lens magnification. The effect of the lens on the image at the focal plane is a transformation of angle to displacement. When the photographer moves the angle of the camera-lens assembly, a point in the image moves on the focal plane. How much it moves depends on the magnification and, in the case of roll, on the distance from the optical axis of the correction servos. Hence, correcting the focal plane by moving it requires measuring the angular motion (rate sensor integration is probably good enough for this) and then calculating focal plane motion to correct it. At the other end of the optics, angular motion can be corrected 1:1 if performed ahead of the lens objective (or 1:2 if certain configurations of mirror stabilization systems are involved).

Nonetheless, building MS into the camera body allows motion to be corrected independently of the lenses, so long as focal length is known. This requires less material, complexity, and cost than making every lens MS. However, the Z, D, N, etc. do not already have MS in the body, so we have to live with whatever is available. To MS the huge number of FA lenses used with the present Pentax MF camera bodies calls for an external stabilizer, or a much lower cost but inconvenient in some cases tripod.

What might be possible, if camera space exists, would be for an affordable upgrade to the 645Z. I suspect that it could only be affordable if a relatively large fraction of the 645Z ownership population were on-board with the idea.
Thanks for that interesting discussion/analysis. In-body SR would be great. However, the Z has such great ISO sensitivity that I can push up the ISO and at the same time push up the shutter speed enough to offset the brighter image, and the fast shutter stops the action, good substitute for SR.

12-25-2019, 03:29 PM   #13970
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QuoteOriginally posted by ivanvernon Quote
Thanks for that interesting discussion/analysis. In-body SR would be great. However, the Z has such great ISO sensitivity that I can push up the ISO and at the same time push up the shutter speed enough to offset the brighter image, and the fast shutter stops the action, good substitute for SR.
Agreed! The vast ISO improvement over the film based N version was a big factor in my eventual acquisition of a Z. One of these days I'll try the D-FA 90 on the N to see how much it helps.
12-25-2019, 03:37 PM   #13971
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QuoteOriginally posted by kaseki Quote
Agreed! The vast ISO improvement over the film based N version was a big factor in my eventual acquisition of a Z. One of these days I'll try the D-FA 90 on the N to see how much it helps.
I should try it on the N as well, but 120/220 film development has become so expensive and so much hassle that I tend to delay. I guess there are lots of folks out there developing their own black and white, but it is too late in the game for me to get involved in chemicals, enlargers, etc.
12-25-2019, 08:12 PM   #13972
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QuoteOriginally posted by ivanvernon Quote
I should try it on the N as well, but 120/220 film development has become so expensive and so much hassle that I tend to delay. I guess there are lots of folks out there developing their own black and white, but it is too late in the game for me to get involved in chemicals, enlargers, etc.

The home development kit for the 120/220 film is actually fairly easy and fun to do. For the printing side if you want to go digital the range of options is so wide which affects the end quality. The bottom line is that a scan of the negative determines the final quality of the picture. I went through a number of scanners before I gave up and bought the z. To scan the negatives to the standard of the z or beyond, the cost at that time was in excess of USD10k for the pro scanner. I did my research, dropped the film the next day, scraped together money and bought the z. Never looked back. Only waiting for the new version now, considering the z is now almost 6 years old. Getting itchy....

12-25-2019, 09:57 PM   #13973
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QuoteOriginally posted by TDvN57 Quote
The home development kit for the 120/220 film is actually fairly easy and fun to do. For the printing side if you want to go digital the range of options is so wide which affects the end quality. The bottom line is that a scan of the negative determines the final quality of the picture. I went through a number of scanners before I gave up and bought the z. To scan the negatives to the standard of the z or beyond, the cost at that time was in excess of USD10k for the pro scanner. I did my research, dropped the film the next day, scraped together money and bought the z. Never looked back. Only waiting for the new version now, considering the z is now almost 6 years old. Getting itchy....
Interesting points.
12-26-2019, 10:13 AM - 2 Likes   #13974
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QuoteOriginally posted by kaseki Quote
... One of these days I'll try the D-FA 90 on the N to see how much it helps.
In retrospect, I have to note three things: (a) I have no idea whether the D-FA lenses even receive power from the 645N in order to perform stabilization; AFAIK, only the iris is actually controlled and lens data read on FA lenses; (b) I am unaware of a version of the Interchangeable Lens booklet that covers the 645 D-FA lenses (please let me know the booklet number if you have one) that might reveal what the various 645 cameras can accomplish with a particular D-FA lens, and (c) I am unaware of a lens interface pin-out schematic for the 645N and 645Z that would reveal useful information of this sort. Lacking a vibration test bench, I guess I will have to just listen for some noise.

Happy Holidays!
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12-26-2019, 11:44 AM - 4 Likes   #13975
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Well, it would be pretty cool if Pentax offered an update to the 645Z to add stabilization to the body. Certainly would be a big thing to help them keep up with Fuji. And I say this having just ponied up a not insubstantial amount of money for the Z and the stabilized 90.
In any case, here's a photo from the first trip with the new(to me) 645Z. Dawn at the Parade of Elephants in Arches NP.
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12-28-2019, 09:45 AM - 3 Likes   #13976
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Panorama of the Las Vegas Strip, about 10 miles away and about 5 miles west of our house.



5 shots stitched.
FA645 80-160mm @143mm
ƒ/11.0
1/200th second
ISO 100

Last edited by Camaro5; 12-28-2019 at 02:38 PM.
12-29-2019, 01:58 PM - 3 Likes   #13977
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---------- Post added 12-29-19 at 02:06 PM ----------





---------- Post added 12-29-19 at 02:33 PM ----------





12-29-2019, 04:07 PM   #13978
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QuoteOriginally posted by BorisKolo Quote




---------- Post added 12-29-19 at 02:06 PM ----------



---------- Post added 12-29-19 at 02:33 PM ----------

No snow yet, Boris? Thanks yet again for the low cost tour of your locale.
12-30-2019, 12:31 AM   #13979
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QuoteOriginally posted by kaseki Quote
No snow yet, Boris? Thanks yet again for the low cost tour of your locale.
Last night we had snofall but very light.

However, photos were made a couple of months ago
12-30-2019, 11:40 AM - 1 Like   #13980
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Snow is falling today, and I thought it would be interesting (at least for me) to see whether flakes could be recorded in the relatively subdued light. I used the 90mm macro with SR ON. Focus was on a tree ~40 ft away. I expected that the high ISO needed for necessary speed would, at worst, just add some more 'snow.' The first image is f/2.8 at around 1/800 at ISO 800. Note near field flake bokeh. The second is f/11 at 1/125 at ISO 3200. Now most of the flakes are in focus, but they have a slight 'star trail' due to the longer exposure. I guess I need a few more stops of ISO. Temperature is 30F/-1.3C, so the flakes are wet enough to fall fairly fast.
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