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08-18-2017, 08:35 PM   #1
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Question about K-1 Liveview using Manual Mode

I took this photo today with my K-1, an MC4 x2 teleconverter and a Sigma 50-500mm lens (set at 400mm). It actually came out significantly better than the Sigma without the TC (enlarged to the same scale) so I was impressed with the performance of the teleconverter.

For those interested, I used a Thousand Oaks "SolarLite" film solar filter, the lens set at f11(manually using the lens f-stop ring since the lens was decoupled from the camera), 1/250s exposure at ISO 800. I used a tripod, 12s shutter delay, and Liveview with electronic shutter. The image is a DNG, adjusted in RAWTherapee and Photoshop.

I think I was lucky with the focus (manually done with the lens) because of a problem I encountered with Liveview (read on).

I had previously used Liveview with just the lens and focused on the set of sunspots using the magnified Liveview image. The sunspots gave me a good focusing reference. Although the Liveview image appeared sharp, some sharpness disappeared when the actual image was captured and examined in review mode - I attributed this the focus peaking used in Liveview as it make the enlarged Liveview image sharpen up a bit.

When I attached the 2x TC, the camera apparently didn't know what f-stop was being used, and the image washed out so much, the sunspots disappeared (and the sun's image was super bright). I tried blocking the lens aperture and closing it down, but the camera compensates and the image just get noisier (due to less light) but stays so bright it still washes out the sunspots (tried darkening the LCD also and that didn't work either)? I finally used focus peaking and focused on the edges of the sun which was the only sharp reference left. That's where I think luck came in because the captured image was about as sharp as I could hope for, but having the spots is a lot more reliable. It may be a foible of the AE system since with the TC, the sun fills more of the image than with the 400mm lens (and there's the totally black background). I had the K-1 set to spot metering for both cases (though I thought that would be irrelevant since I was in manual mode).

Is there any way to bring the image back down in brightness with the decoupled lens (due to the 2x TC) so I can see the sunspots for a focusing reference?

Note in this image, solar granulation can be seen as well as limb darkening (darkening at the edges of the sun due to the "horizon" of the sun and the surface angle relative to the viewer). The sun is pretty much clear right now other than these few spots so the corona this Monday should be rather bland compared to its appearance when the sun is more active. I also attached the uncropped K-1 frame for reference (approximately 800mm equivalent focal length - though not to full K-1 resolution, of course).

Anyway, if someone knows how to tame the K-1 Liveview gain, let me know. Thanks.

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Last edited by Bob 256; 08-18-2017 at 09:03 PM.
08-18-2017, 08:53 PM   #2
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QuoteOriginally posted by Bob 256 Quote
Anyway, if someone knows how to tame the K-1 Liveview gain, let me know. Thanks.
I've found that stopping the lens down using optical preview is one reliable approach, since you can't force the camera to darken the image beyond a certain point.

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08-18-2017, 09:08 PM   #3
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QuoteOriginally posted by Adam Quote
I've found that stopping the lens down using optical preview is one reliable approach, since you can't force the camera to darken the image beyond a certain point.
I'll try the OPV but it won't stop the lens down since the lens is mechanically decoupled from the camera and set at a fixed f-stop using the f-stop ring on the lens. The f-stop readout on the LCD screen is blank since the camera can't read the lens setting.

I tried manually stopping the lens down but the camera compensates and the LCD image stays bright with increased noise.
08-18-2017, 09:55 PM   #4
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QuoteOriginally posted by Bob 256 Quote
I'll try the OPV but it won't stop the lens down since the lens is mechanically decoupled from the camera and set at a fixed f-stop using the f-stop ring on the lens. The f-stop readout on the LCD screen is blank since the camera can't read the lens setting.

I tried manually stopping the lens down but the camera compensates and the LCD image stays bright with increased noise.
Another thing you can try is focusing my judging the amount of CA around the edge of the sun. Even when overexposed, the size of the fringe should be discernible. I had a similar problem when shooting the moon with a long lens, and it worked out after a bit of trial and error.


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08-18-2017, 09:55 PM   #5
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QuoteOriginally posted by Bob 256 Quote
I'll try the OPV but it won't stop the lens down since the lens is mechanically decoupled from the camera and set at a fixed f-stop using the f-stop ring on the lens. The f-stop readout on the LCD screen is blank since the camera can't read the lens setting.
If you are using the aperture ring to set the iris opening, use M mode with "Aperture ring enabled" in the custom settings menu. OPV should work under those conditions as should aperture actuation and stop-down metering.* EC may be used to darken the live view display, though as Adam mentioned, there are limits. With a few quirks, you may also use the aperture ring in X and B modes to control the aperture for exposure and DOF preview.


Steve

* There is one major qualifier, that being that the mount face on the lens must be electrically conductive.

Last edited by stevebrot; 08-18-2017 at 10:28 PM.
08-19-2017, 01:43 AM   #6
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I have the same problem when focusing on the moon with an old manual lens. Spot metering and really make sure the moon (which has to be nearly full) is in the center of the frame. If it's not perfectly in the center and large enough to cover the spot metering area it will be washed out in live view.
So it "should" work with 2x400mm and spot metering in my experience, but only with the moon/sun centered.
08-19-2017, 06:34 AM   #7
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Make a disc to cover the front of the lens. Then make a small hole in the center. This will greatly reduce the amount of light entering the lens and have no effect on image quality.

08-19-2017, 07:37 AM   #8
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In live view switch to AV and bring exposure compensation down, that will darken the screen
08-19-2017, 01:45 PM   #9
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Thank's folks. I've tried most of those with the exception of using AV and exposure compensation which I'll try.

I do have "aperture ring enabled" and the lens is conductive but no-go. Tried the aperture reduction but the image just gets noisy and stays washed out. Also by reducing the aperture, the depth of field is increased and the exact focus gets even harder to find.

The sun was almost perfectly centered and filled about one-fourth of the frame and I didn't see any difference when its position shifted. Could be it's just not large enough to cover the spot metering area and the black background rules.

I think I can make out by using focus sharpening on the rim of the sun but will try the AV approach next time which may be Monday the way things are going at present. A lot of prep for the eclipse right now. Shot some photos of the approaching moon and Venus this morning - a little closer tomorrow, and then blot-out. Will let everyone know if I get a working solution.

So far, no hoards of people in my neck of the woods but that could change as they might be driving this way as I type.

Last edited by Bob 256; 08-22-2017 at 02:49 PM.
08-19-2017, 02:01 PM   #10
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You can make the sun appear bigger for the spot meter by shooting in aps-c mode.
08-19-2017, 02:09 PM   #11
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QuoteOriginally posted by Gimbal Quote
You can make the sun appear bigger for the spot meter by shooting in aps-c mode.
Ah, I didn't think of that and it would be easy to switch. In fact, I could be shooting in APS-C mode since the same number of pixels are involved and a crop like I used in my original post would already be done. Will definitely give it a try.

I want to pop back out to FF for totality though to capture all of the corona but with the K-1 it's as easy as using the small function dial.
08-19-2017, 10:46 PM   #12
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Tried the AE button and APS-C Mode and no luck - still stuck with washed out sun. Interesting though - some clouds floated over the sun while I was trying these, and they dimmed the sun enough that I could see the sun spots and get a focus. It must be something misleading the K-1 autoexposure system which then tries to emulate the scene on the LCD to appear as it would be shot. In this case, it's boosting the image brightness too much (the actual photo can actually be greatly underexposed and doesn't relate to the LCD preview version relative to exposure. I'll try to play around some more tomorrow before I head off to the great eclipse thing.
08-20-2017, 03:04 AM   #13
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QuoteOriginally posted by Bob 256 Quote
Tried the AE button and APS-C Mode and no luck - still stuck with washed out sun. Interesting though - some clouds floated over the sun while I was trying these, and they dimmed the sun enough that I could see the sun spots and get a focus. It must be something misleading the K-1 autoexposure system which then tries to emulate the scene on the LCD to appear as it would be shot. In this case, it's boosting the image brightness too much (the actual photo can actually be greatly underexposed and doesn't relate to the LCD preview version relative to exposure. I'll try to play around some more tomorrow before I head off to the great eclipse thing.
I've been having the same problems finding the best focus and exposure settings with the Maksutov 500mm mirror lens I purchased for the eclipse, which if I recall correctly was one of your recommendations in a previous post - thanks for that. This lens is a fixed f8 and totally manual, thread mount lens. The camera is a K-1. I don't know if it's any help but here's what I did. After a lot of practicing I hope I'm ready for the eclipse.

Focus I determined in two ways: 1). I took a series of photos, I guess it could be called focus bracketing, with the lens set at infinity and 3 shots on each side of infinity, then looked at them enlarged on a photo editing monitor. 2). I used the magnification in LV which made it fairly easy to visually judge focus. Both methods gave the same results - focus was sharpest exactly at an indicated infinity.

For exposure I did a lot of test shots with bracketing, again looking at the results on a photo editing monitor. At the time of the eclipse here the best exposure was at 1/30 plus minus with iso set at 200, and the only option being f8. I did several bracketing settings and settled on 1 1/2 stops, 5 exposures.

I did a lot of internet research on mirror lenses and, as you said, most opinions were that the old Russian built Maksutov designed ones were the sharpest. Cost was important for me - this one only cost me about $140 from a US seller on ebay, is in excellent condition and I believe it will good results with the eclipse, although it certainly is awkward to use but that's minor as long as the results are good. Thanks again.

Last edited by wanderer2; 08-20-2017 at 03:22 AM.
08-22-2017, 12:46 PM   #14
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QuoteOriginally posted by Bob 256 Quote
It must be something misleading the K-1 autoexposure system which then tries to emulate the scene on the LCD to appear as it would be shot.
It is a little more complex than that. One of the early criticisms of the K-1 and other Pentax dSLRs is that live view brightness generally does NOT emulate exposure settings in a consistent manner.* Generally, gain is adjusted to provide consistent overall brightness using meter input as a guide (hence the spot meter hack). Notice that I said "generally". That is because the K-1 does support exposure emulation in live view for the following specific cases:
  • Auto-exposure modes when EC is invoked. Apply negative EV and the display will dim.
  • M mode for both aperture and shutter with the body setting the aperture. Underexposure dims the display.
  • M mode using aperture ring on the lens and EC is invoked.
The last case is the most useful if one has a lens with an aperture ring. One can make the exposure settings in advance and dim the display to focus without changing the set EV.


Steve

P.S. Yes, spot metering may also dim the display, but is sort of a blunt tool to the task.

* The case in point was for stacked images in macrophotography where the photographer desired visual guidance for both brightness and DOF while dimming the far members of the stack for subject isolation. Apparently certain other brands are friendlier to the task and he had recently moved from one of those.
08-22-2017, 02:41 PM   #15
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So run me through the process - I'm using a mechanically decoupled lens in manual mode with the lens setting the aperture (and the camera setting the shutter speed) - what button sequence do I use to invoke EC, and when I do that, will it affect the actual exposure or do I need to undo the EC before taking the picture?

I managed to work through focusing yesterday by using the clipped edge of the sun though that was somewhat uncertain, but in the future focusing on sunspots (which I shoot from time to time) would be a great help. And of course, there's 2024 coming

Last edited by Bob 256; 08-22-2017 at 02:54 PM.
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