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UltravioletPhotography

UAT on Sony a7R-BB: A little about each


Andrea B.

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Here are some test shots made with the Asahi Ultra-Achromatic-Takumar 85/4.5 on my Sony a7R full spectrum conversioin. I have typically used the UAT on a Pentax K5-BB with an inlaid M42-K mount adapter. But I think I like this lens better on my new Sony a7R even though the long M42-E mount adapter for the UAT does make for a slightly awkward configuration.

 

As I hope everyone is fully aware, I am not much of a "tester". More of a casual demo provider, perhaps. :D So I don't put up charts and look for brick walls. I simply try to use a lens and/or camera in the normal way and keep an eye out for any problems which might occur. I show all my mistakes as well. That might help someone else not to make the same error.

 

Having the a7R's Focus Peaking and Zebra Stripes is new to me. I can't say I did all that well with Focus Peaking, as you will see in the White Blossom shots below. Seems to me like Focus Peaking can get in the way and obscure things. Time will tell on this one.

 

Focus Peaking seems not to show up on some subjects. While it does appear in UV and IR sometimes, I'm not sure it is all that useful to the UV effort. It is early days with the a7R, so I need to experiment more with FP settings before I decide whether to turn it off permanently.

 

The Zebra Stripes are intriguing. What I am trying to learn is how well they correlate to R, G or B channel saturation and the Luminosity histo of the a7R. Of course, those histos seem to be for jpgs only. There might very well be ample headroom in the a7R raw AWR files to overexpose and pull back so I'm looking at how much more EV I can add after the Zebra Stripes first appear.

 

Camera: Sony a7R-Broadband

Lens: Asahi Ultra-Achromatic-Takumar 85mm f/4.5

 

Adapter: Fotodiox Pro M42-Nex (Type 1)

Tripod: RRS Ground Pod

Ballhead: Manfrotto Pistol Grip 327RC2

Accessories: Vello BG-S2 Battery Grip and Vello Freewave Plus Wireless Remote

 

Focusing: Wide-open at f/4.5 via Live View with use of Magnifier configured under AF/MF button. Then stop-down to desired aperture and recheck with Magnifier when possible. I experimented with Focus Peaking as mentioned above. Currently it is set to a white colour. I switched between the Lo and Mid settings.

 

DRO: I am particularly interested in the Sony D-Range Optimizer (DRO) setting which I have configured to be easily accessible via the C2 button. I also have it in the Fn list. DRO has 5 levels plus an Auto setting. On my Nikon D600-BB, I very often used the similar in-camera ADL setting to broaden range in scenes of high contrast, particularly our dark UV photos. The Sony DRO setting seems to be a bit broader, so more experimentation will be needed to decide how far to push it in each of Visible, UV and IR scenarios.

 

 

White Blossoms Visible [f/16 for 1/80" @ISO-50, Matrix Metering, Auto DRO, Baader UV/IR-Cut Filter]

1200 pixels wide

  • I tried to focus this shot using only Focus Peaking. And did not do particularly well. I have not yet figured out the nuances of this focusing tool. Perhaps FP is more useful in close to medium range work?
  • I was more successful using only Zebra Stripes to set exposure. The displayed +/- EV (when camera is used in Manual mode) seems to have about a 1/3 stop leeway before Zebras increase/decrease.
  • And of course, there is probably an interesting interaction between DRO and Zebras which must be worked out.
  • My initial impression of Auto DRO is that it is probably best to directly set DRO to one of the 1-5 levels. No surprise there as many Auto tools are like that - good sometimes but not always.
  • The UAT + a7R combo is excellent for capturing masses of detail.
  • Photo was converted in Photo Ninja 1.3.1b.

DSC00851pn02.jpg

 

 

White Blossoms Visible [unresized Crops]

1160 pixels wide

 

Unresized crop: I thought I was focusing on these frontmost flowers. Oh well.

DSC00853pnCrop1.jpg

 

Unresized crop: Branches are nice and sharp against the sky. There's a bee blur too.

DSC00851pnCrop2.jpg

 

Unresized crop: Lower right, no signs of CA. Still so much detail on the distant trees in the background. Nice lens, I'd say.

DSC00853pnCrop3.jpg

 

Unresized crop: Well defined tangle in back of the unfocused blossoms.

DSC00853pnCrop4.jpg

 

 

White Blossoms Ultraviolet [f/16 for 1/1.2" @ISO-200, Matrix Metering, Auto DRO, BaaderU UV-Pass Filter]

1200 pixels wide

  • ISO-200 was not quite high enough to be able to stop motion. So there are some breeze blurs from the Norwegian gale which blew in yesterday during the experiment.
  • I was slightly better with the focus but there were not as many FP twinkles in UV as I would like were I to use FP regularly.
  • Tree branches against the sky are, shall we say, an "acquired taste" in UV. Perhaps some wild curve settings would make some interesting abstraction out of this? Maybe later. The colours here resulted in trying to move purple towards blue.
  • Oversample, then resize downward and what do you get? Apparent increases in sharpness/detail/etc. At least it seems that way to me today. I hope it does not appear horrible to me tomorrow!

DSC00864pn.jpg

 

 

White Blossoms Ultraviolet [Raw Composite]

  • Raw Digger shows the Red channel to be about 7% overexposed and the Blue channel to be about 5% underexposed. You can't win in UV.
  • No sharpening. No edits. Only demosaic, gamma and histo scaling.

DSC00864rawComp.jpg

 

 

White Blossoms Ultraviolet [unresized Crops]

1160 pixels wide

 

Unresized crop: Branches on the upper right are less sharp because I did manage to pull focus slighly more forward in the UV version.

DSC00864pnCrop0.jpg

 

Unresized crop: Lower right. Still no signs of CA.

DSC00864pnCrop01.jpg

 

Unresized crop: Some actual focus at 100%. A bit of noisy grain stuff was induced by using the Detail slider in Photo Ninja. It's currently all or nothing and cannot be brushed into only the areas where you want it. See the next raw composite crop to verify there was no noise in the original at ISO-200.

DSC00864pnCrop02.jpg

 

Unresized crop: Raw comp crop. No sharpening. No detail slider. No noise. Raws are really raw looking.

DSC00864rawCompCrop.jpg

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Andy Perrin
Andrea, I gather the focus peaking works by edge detection, which means it's naturally going to work best when you have an isolated subject in front and a very blurry background behind it. So these tangled bushes and tree limbs are kind of a worst-case scenario for that algorithm, since it's going to pick up on every branch and not be able to distinguish foreground from background. I would think it would be better for focusing a macro shot, with the tiny depth-of-field?
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Don't know. :D

Focus Peaking is very, very subject dependent. Either near, medium or far there seems to be some subjects which simply do not Focus Peak. Not enough edge contrast I suppose. So far I haven't done any better in close shots than I have in far shots. But as noted, it's early days on the a7R so experience must be gained and nuances must be worked out. We shall see eventually how all this plays out.

 

Using the a7R LCD focus is most easily attained just as I do on the D600 or D810. Kinda scootch back & forth to get in the focus ball park and then Magnify to refine focus. For the scootching part, Focus Peaking is somewhat helpful. I think D810 has a slightly better Magnify, but that certainly does not imply the a7R Magnify is not good. It is.

 

I am wondering whether the presence of filters and especially dichroic filters may play some role here?

 

I was at f/4 when I tried to focus on white flowers way up there in that tree. Maybe that isn't wide enough?

 

Another observation: when both FP and Zebras are on, then the LCD can sometimes enter Twinkle & Dance mode if exposure is too far off and I get slightly seasick.

:lol: :wacko: :blink:

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Andy Perrin

I played with the focus peaking on my camera a bit after this, and it certainly seemed to help in the macro shots of my nice (bright) dandelion on the dark background? Compare this pic to the one in the dichroic filter problem thread yesterday! There is still some blur around the far edge, but I attribute that to my so-so photography skills at this point.

 

(330WB70, Noflexar, F8, 1/15", iso3200, focus peaking, exposure noise and colors tweaked in PN and Photoshop)

post-94-0-99006800-1460670850.jpg

 

1:1 pixel ratio, everything off in PN except white balance:

post-94-0-33564600-1460671306.jpg

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