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11-20-2012, 08:50 AM   #46
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Flash sync. Help me with my understanding.
Flash actually fires, as in the flash tube itself and resulting light output, in the nanosecond range.
That is, the electric current from the capacitor discharge is stong enough to arc across the flash tube and cause a flash. The light from the flash tube hits the subject at the speed of light.

The flash therefore has three possibilities interacting with the subject.

1) To fill in the shadows.
2) To overpower the available light.
3) In complete darkness, to act as a "shutter".

Since the light itself is traveling at the speed of light, then the only important thing, is for the flash to fire at the right time of the shutter.

1/60 or 1/250 or whatever shouldn't make any real difference when dealing with moving objects as the flash itself is fast enough for anything. Am I missing something?

As for flash power settings, I'm not sure if it's about the amplitude or the duration that is set in the power settings.

11-21-2012, 09:30 AM - 1 Like   #47
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QuoteOriginally posted by LaurenOE Quote
Since the light itself is traveling at the speed of light, then the only important thing, is for the flash to fire at the right time of the shutter.

1/60 or 1/250 or whatever shouldn't make any real difference when dealing with moving objects as the flash itself is fast enough for anything. Am I missing something?
This is true. A technical challenge though is getting equal distribution of that short-duration flash illumination across the entire image -- traditionally this means the flash burst should be timed such that it occurs during a moment when the shutter is fully open (entire film/sensor area is exposed). Mechanical shutters will have a portion of time at the beginning and end of the exposure where the shutter mechanism is still in motion and part of the image is obscured. With a focal plane shutter this is typically a leading & trailing curtain -- one curtain opens in one direction, then a second curtain closes in the same direction. For slower shutter speeds, there is a period of time between the first and second curtain where the entire imaging area is exposed. The maximum shutter speed where this happens is known as X-sync. For speeds higher than this, the trailing curtain begins obscuring one side of the image before the first curtain has fully exposed the opposite side -- so the exposure is a 'slit' that moves across the image plane. HSS is a trick for shutter speeds faster than X-sync where the flash is strobed in multiple lower-power bursts several times during the shutter curtain travel so that the entire frame gets even flash illumination.

If your question is why do we care about 1/60 vs. 1/250 -- the problem is when using for fill flash (daylight sync) if you're limited to 1/60 (or even 1/250) you may be forced to stop the aperture down a bunch to avoid overexposure -- this makes it difficult to shoot with large aperture (for depth-of-field management) + flash in daylight. You can use a neutral density filter to cut the light but that cuts your available flash power dramatically as well. On the Q in particular, you want to shoot with larger apertures most of the time to limit the effects of diffraction and preserve the already very limited ability to blur backgrounds.

Also, most exposures are a combination of flash AND ambient light. The lower the shutter speed (e.g. 1/60 as you mentioned), the greater contribution from ambient light. This may mean that any subject motion may still produce some blur -- the main exposure from flash might look pretty sharp but there may be some blur trails to/from that main exposure.
11-21-2012, 01:26 PM - 1 Like   #48
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Hi Lauren,

Andrew's answer is very good -- much more succinct than the one I started. . .

Since we're talking about the Q and adapted lenses, I'll add a practical application where this comes into play.

The Q has always had the potential to be a very effective macro shooter, especially for high magnification of small critters. The crop factor adds apparent magnification -- though actual magnification is the same, smaller subjects more completely fill the frame of the image captured, so they appear larger -- by a factor of 5.58x compared to 135mm and @ 3.6x compared to APS-C. Also, the same subject size to frame perspective can be achieved at longer shooting distances, so I can get deeper DOF for a given f stop, less subject intimidation, and better flash angles for camera mounted flash. This type of shooting is easiest for me handheld with flash used as the primary lighting source to help overcome camera shake and subject motion. The Q's much smaller size and lighter weight makes the usually awkward shooting positions considerably easier to achieve and maintain, and shooting at larger apertures requires less flash power, so smaller flash(es) reduce the weight even more.

Until the release of the Pentax OEM K2Q adapter, there has been a stumbling block to using the Q for this type of shooting -- and it's a big one. 1/13 flash sync with adapted lenses makes it virtually impossible to use flash outdoors in daylight. It's doable, but not practical, even with the overwhelming advantages the Q offers for this type of shooting. With the Pentax K2Q adapter and its integral shutter, it'll be easy, so it will be worth the price for me, just for this.

Scott
11-21-2012, 07:13 PM   #49
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Adapter arrived today from Crutchfield. Have had to spend a bit of time straightening out the firmware and focus peaking; hopefully will have some time tomorrow to try outdoors in good light.

11-21-2012, 07:32 PM   #50
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QuoteOriginally posted by baro-nite Quote
Adapter arrived today from Crutchfield. Have had to spend a bit of time straightening out the firmware and focus peaking; hopefully will have some time tomorrow to try outdoors in good light.
What kind of "problems" did you encounter when updating the firmware/peaking for the adapter?

JP
11-21-2012, 07:50 PM   #51
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No problems other than shake reduction was disabled. The firmware instructions do say that the 1.10 update also updates the 1.01 update; I just didn't read that carefully the first time.
11-21-2012, 09:41 PM - 1 Like   #52
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QuoteOriginally posted by panoguy Quote
Well, maybe not so simple, since it has multiple (captive) moving parts, and that narrow arca-type clamp must be strong enough to hold the DA*60-250 sideways!
I've already sent out some inquiries...
Just an update on this. I am sending out my DA*60-250 tripod foot to a (very experienced) contact in Hong Kong for reverse engineering. First prototypes should be only a few weeks away!

Also, considering some comments here, creating a "ring clamp" with a tripod foot (so the foot can be rotated around the adapter) may also be in the offing. Obviously, a "claw-type" (like the OEM) foot replacement would also work for the DA*300 and DA*60-250 lenses, so that's the best direction to start.
11-21-2012, 09:52 PM   #53
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QuoteOriginally posted by panoguy Quote
Just an update on this. I am sending out my DA*60-250 tripod foot to a (very experienced) contact in Hong Kong for reverse engineering. First prototypes should be only a few weeks away!

Also, considering some comments here, creating a "ring clamp" with a tripod foot (so the foot can be rotated around the adapter) may also be in the offing. Obviously, a "claw-type" (like the OEM) foot replacement would also work for the DA*300 and DA*60-250 lenses, so that's the best direction to start.
Now that's great news! I look forward to updates as the project progresses. Thanks!

11-21-2012, 09:58 PM   #54
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Good news. Agree with snostorm. A rotating clamp would be really nice. Before the Pentax adapter arrived I thought the tripod foot was going to rotate. It does on the 300. Didn't realize there was a seperate ring on the 300.

Had a chance to compare the 60-250 and DA*300 tripod feet. Surprised to find they aren't the same size! The 60-250 foot is taller. Luckily the attachment mechanism works the same way. I was able to attach both to the Q.
thnks
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11-21-2012, 10:07 PM   #55
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QuoteOriginally posted by barondla Quote
Had a chance to compare the 60-250 and DA*300 tripod feet. Surprised to find they aren't the same size! The 60-250 foot is taller.
Yep, found that out at the same photo expo where I tried out the OEM adapter with the 300 foot. My thoughts are to make it to the same height as the 60-250 foot, but with arca-swiss grooves on the footplate sides (no need for another lens plate), as well as the usual 1/4" threaded hole in the middle. I'm also thinking the footplate should be longer than the OEM (maybe 80mm total?)...
11-21-2012, 10:34 PM   #56
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Careful making it too long. It has to clear the foot that is on the lens! On my 300 I would have to mount the adapter's foot backwards ( folded under the Q body to clear the other foot). This is using two of the 300 feet. The 60-250 ring may be placed further forward and allow more room. Being taller, the 60-250 foot might clear the 300 foot since they would be concentric.

Love the built in Arca plate.
thanks
barondla
11-22-2012, 07:28 AM   #57
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Great initiative panoguy! I want one by the end of next week so unless it is exorbitant I will order from Pentax USA (closed till Monday). While on the topic, would someone please tell me what is the length of the DA*300 foot? If I buy one I'll need an Arca-Swiss plate to go with it. I realize I may need to order a longer plate to be able to balance the DA*200.
11-22-2012, 08:04 AM   #58
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QuoteOriginally posted by panoguy Quote
Yep, found that out at the same photo expo where I tried out the OEM adapter with the 300 foot. My thoughts are to make it to the same height as the 60-250 foot, but with arca-swiss grooves on the footplate sides (no need for another lens plate), as well as the usual 1/4" threaded hole in the middle. I'm also thinking the footplate should be longer than the OEM (maybe 80mm total?)...
While cruising around for deals online prior to the family get-together I found that Opteka makes replacement telephoto ring tripod mounts for lenses. For example: Amazon.com: Opteka Tripod Collar Mount for the Canon EF 70-200mm f/4L USM, EF 300mm f/4L USM, & EF 400mm f/5.6L USM SLR Lenses: Warehouse Deals

I'm wondering if any of the existing tripod collar adapters would fit the Pentax OEM Q-K adapter?
11-22-2012, 08:12 AM   #59
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I'd make one..but I don't have a boring head large enough to cover the diameter of a lens/adapter.
I think the most I can make is something like 2". Besides, my milling machine is totally manual. I would have to remove a TON of metal to get it down in weight.

I'm in for buying whatever becomes available.

11-22-2012, 08:37 AM   #60
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QuoteOriginally posted by barondla Quote
Careful making it too long. It has to clear the foot that is on the lens! On my 300 I would have to mount the adapter's foot backwards ( folded under the Q body to clear the other foot).
Hmmm... that is a concern. Reversing the foot and not hitting the camera is probably why the Pentax OEM one is so short (it's length certainly doesn't allow balancing the weight of the lens + camera body over the tripod!). The idea is that if we build-in arca grooves, there is no need for a lens plate, so making it longer allows for some fore-aft balancing on arca support systems.

QuoteOriginally posted by baro-nite Quote
Great initiative panoguy! I want one by the end of next week so unless it is exorbitant I will order from Pentax USA (closed till Monday).
If you manage to order one, let us know what it cost you...
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