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Forum: Mini-Challenges, Games, and Photo Stories
01-26-2024, 04:19 PM
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Red Moon over ocean, Barcelona 2022.
K1 and DA*200
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Forum: Pentax K-3 III
06-13-2021, 12:21 PM
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I haven't tested it any further due to rain and bad weather. But others have. It is combination of 2s self-timer and horizon correction that causes the problem. Turn off horizon correction and there's no problem apparently (haven't tested it myself yet - but that seems to be the consensus).
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Forum: Pentax K-3 III
06-10-2021, 11:44 AM
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That looks like the results out of a Helios 44! I've often been disappointed by the lack of swirly-ness on APS-C with my Helios, maybe I can use this as a swirly-ness accentuator. Pentax should (a) fix this, but (b) include it in future firmware as a Helios simulator.
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Forum: Pentax K-3 III
06-10-2021, 09:57 AM
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Here is a 100% crop of the upper left corner. Sorry couldn't figure how to add to edit this into my original post.
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Forum: Pentax K-3 III
06-10-2021, 09:38 AM
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Now I know what was going on. A week ago I was out for a walk and took a break at a picnic pavilion to escape the heat for a minute. Played with the camera and settings for a bit while I was there. I was in for a surprise when I got them on the computer at home. What a swirl effect.
The lens was the DA 60-250 with the DA 1.4 teleconverter on, which gave a focal length of 84mm. I was looking to see the effect of diffraction, but not in any real scientific way since I just did one run through. I had set the camera to 2-sec delay (which I have set to turn off SR), Horizon correction is set to on. The camera was setting on the top of the a solid, non-jiggling, picnic table. I didn't do any attempts to recreate the effect just marked it down to operator error for someone with a new camera. The swirl effect was obvious between 1/30 to 1/125 sec. The corners were pretty bad at all the speeds I used.
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Forum: Pentax K-3 III
06-10-2021, 04:03 AM
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I would comment that I think it is perfectly possible that neither SR or anything else is specifically wrong, but that the physical actions in this scenario lead to masses being moved in a way that it creates a resonance/freuqnecy of shake that is not fully dampened on a tripod when shutter speed is 1/125 sec.
I bet the 2 sec mirror lock thing is not present in handheld modes (because of proper dampening).
I can imagine that the acceleration and deceleration of a shutter to 1/125 sec speed in the specific process done for 2 sec MU is actually causing it.
All these vibration shake things 100% depend on a) the resonance frequencies of the combined physical items (body + lens + tripod head + tripod) and b) the quality of dampening available (hands are good, ash wood tripods are good; metal or even worse carbon tripods are bad).
For the people with some scientific interests here two videos showing resonant frequencies:
You Tube
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src="https://www.youtube.com/embed/LV_UuzEznHs?controls=1" allowfullscreen>
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and
You Tube
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src="https://www.youtube.com/embed/rvwwQAfdBWs?controls=1" allowfullscreen>
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Forum: Pentax K-3 III
06-10-2021, 04:18 AM
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Forum: Pentax K-3 III
06-10-2021, 03:44 AM
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Yesterday I tried to recreate Dpreviews findings that the K3 III will not give sharp images at 1/125s when the camera is mounted on a sturdy tripod. The theory is that it is due to shutter shake.
To my surprise I got the same results. It is not due to shutter shake however.
I used the camera on a tripod and engaged the 2s self-timer that locks up the mirror. I shot first at the metered shutter speed (quite slow; 1/5 - 1/2s) at 100ISO, then boosted the ISO until the speed was 1/125s. The slower shutter speed images were sharp; the 1/125s weren't. The fuzzy images were sharper in the center and gradually worse towards the edges. Worst at the far edges. At the far edges it can be seen that the subject is streaked; like like start trails at long exposure. Ie the fuzzyness is due to rotation. This can also be deduced from the fact that the two images were slightly rotated compared to each other in spite of the fact that they were shot few seconds apart while mounted on a tripod.
It is clear that the sensor is rotating during exposure. SR is supposed to be off when using this mode. I tried to turn SR off manually, but the camera (naturally) says that SR is not available in this mode.
It seems like the SR is on or malfunctioning in 2s mirror lock mode.
I tried to shoot at 1/125s in normal manner; that is without mirror lock. All images turns out super sharp. Hence, there's no shutter shock (or mirror slap for that matter) at 1/125s.
I hope this is a bug that can be fixed in software. Either SR is on during 2s self timer mode or it is malfunctioning somehow in this mode. My camera has Firmware 1.01.
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Forum: Mini-Challenges, Games, and Photo Stories
06-29-2020, 05:01 PM
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KP + DA*300 + 1.4x
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Forum: Troubleshooting and Beginner Help
09-17-2017, 06:56 PM
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Welcome to the Pentax Forums!
It is supposed to do that. The aperture on all* K-mount lenses your open to their maximum as the lens is mounted. Lenses that use the aperture ring to set the opening will only stop down at exposure time and to meter if the following conditions are met:- Aperture ring enabled in custom menu settings
- M mode
- Auto-ISO OFF
That last point is the tricky one. The combination of auto-ISO and M mode causes the camera to fail-over to TAv mode meaning that the aperture ring on your 50/2 remains wide open. I hope this helps.
Steve
* Well, almost all K-mount lenses. There are a few that have fully manual or preset aperture mechanisms which are not coupled to the camera's shutter action, but they are not common.
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Forum: Troubleshooting and Beginner Help
08-30-2016, 08:13 AM
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It is not supposed to move when you turn the ring. Only during shot, or for "green-button" metering. It will be wide-open the rest of the time if mounted and the camera is on. (I think on the K-01 it opens up when you power it up cause it is mirrorless -- every DSLR model it is open if mounted.)
Camera should be in M mode, and TURN OFF auto-iso (this is usually the gotcha -- it is in TAV mode on K-01 if auto-iso is enabled, not true Manual. ISO must be set to fixed number).
See here, if you haven't already:
https://www.pentaxforums.com/forums/54-pentax-lens-articles/110657-how-use-me...k-x-k-7-a.html |
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Forum: Troubleshooting and Beginner Help
08-30-2016, 11:07 AM
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Not just every DSLR, but most SLRs too. It is called open-aperture metering. If you turned the aperture ring and the aperture closed before you took the picture, the screen (or viewfinder in other cameras) would become too dark to focus or even see, depending on the aperture. The lens will stop down to your chosen aperture once the exposure is taken.
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Forum: Mini-Challenges, Games, and Photo Stories
06-06-2020, 11:38 PM
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Shot last week, using Pentax Q7 and a 480mm f/6 telescope.
Moon, 2020 May 31 by k kwb, on Flickr
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Forum: Monthly Photo Contests
07-15-2019, 03:37 PM
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Voted for the one that was the least Photoshop'd
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Forum: Pentax K-r
05-17-2019, 07:13 AM
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Hi and welcome to Pentax Forums.
What camera are you using? Knowing that might help others understand your concerns, and be better able to help you out.
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Forum: Mini-Challenges, Games, and Photo Stories
12-25-2018, 02:55 PM
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Lovely shot Anjana. Look forward to seeing more tea plantations.
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Forum: Post Your Photos!
12-23-2018, 10:02 PM
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I like this! Very creative! Good work!
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Forum: Welcomes and Introductions
12-18-2018, 04:36 AM
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Welcome from down south Waiyne!
I've got a KP on the way myself. Looking forward to it.
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Forum: Monthly Photo Contests
12-12-2018, 10:25 AM
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I would like to nominate this photo
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Forum: Monthly Photo Contests
12-10-2018, 09:57 PM
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I would like to nominate this photo
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Forum: Monthly Photo Contests
12-10-2018, 05:39 PM
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I would like to nominate this photo
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Forum: Monthly Photo Contests
12-10-2018, 02:36 PM
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To me, this exemplifies the definition of negative space without creating it artificially. Nice photo.
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Forum: Monthly Photo Contests
12-10-2018, 08:25 AM
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I would like to nominate this photo
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Forum: Monthly Photo Contests
12-09-2018, 04:25 PM
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I would like to nominate this photo
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