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sharpasaknife2.jpg
28-Oct-2013 Tom Brown

sharpasaknife2.jpg

Nikon D800
1/60s f/8.0 at 50.0mm iso100 full exif

other sizes: small medium large original
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Tom 04-Nov-2013 18:58
Thanks, Lasse.

Unfortunately, I didn't take a RAW image of that picture, but I will recreate it and send it so you when I have a chance.

Ronniemac - how can you tell the barrel distortion? Is it the straight side of the blades? I don't have a good I for picking that stuff out of images.
As for the sharpness, if you take this image and apply Blur 2X, you will get pretty close to the out-of-camera sharpness settings. I think it might be all the tiny details have blown highlights from the flashes which gets brought-to-light so to speak with sharpening the image. I therefore blame image weirdness on speedlights rather than PhotoShop.
Lasse 03-Nov-2013 21:09
This is out-of-camera? Wow...
If you'd like to talk about demosaicking, please contact me at preamp@web.de
Just send me the RAW file and I'll willingly try some converters and show you the differences.
ronniemac03-Nov-2013 12:08
Looks a tad over sharpened, with a hint of barrel distortion on some corners. Nice!
Guest 01-Nov-2013 20:39
Lasse, thanks for the tip. Is the checkerboard pattern the one that's visible when you zoom in 1600%? In that case, I think I see it.
How do you normally debayer an image after the fact?

This is an out of the camera JPEG with factory settings, but an inter-webs search just now yielded that an in camera debayering algorithm may in fact be better than an external RAW converter:
colormancer.com/whitepapers/RAW/is-RAW-always-better.htm

I guess I will need to enter a "Sharpest Corner with Best De-Bayering for Smooth Pixel Viewage >400%".
Tom 01-Nov-2013 19:02
Addendum:

This image is so sharp that its JPEG weighs 44MB at PhotoShop quality level 12. Apparently the secret to handling the high resolution of the D800 is to shoot strictly in a high Bokeh environment (the Bug Bokeh image is only weighs 6MB).

I first submitted the D800 factory setting JPEG output. Then, realizing that would be a handicap against the competition. The image was 2x sharpened in Photoshop. Anything more, while definitely sharper, made the image a little synthetic viewed up close.

More info: one speedlight with diffusion dome two feet to the right and one speedlight with diffusion dome just to the left and above the camera. The camera itself was about 18" from the ground.
Lasse 01-Nov-2013 19:00
Tom, you should try another debayering/demosaicing method, because there're lots of small areas with checkerboard patterns visible. Don't know how to do this with CS6, though.
Lensrentals29-Oct-2013 12:34
Apologies for poor center sharpness - the lens either has some focusing problems, or I'm taking a picture of a three-dimensional object.

Sharpest corner, from least sharp to sharpest:
Top right is the least sharp - it gets used daily and isn't sharpened as frequently as it should be (chef's knife).
Bottom right - more jagged than sharp, more tears through things than cuts (steak knife)
Top Left - very sharp and the serrations by and large keep the cutting edge protected while banging around in the drawer (bread knife).
Bottom Left - The sharpest corner of all, mostly because that corner only gets used every Thanksgiving for carving up a boneless turkey prior to cooking and gets extra attention during sharpening (filet knife).

Oh, as for the lens? I don't know what the sharpest corner is or how it compares to others, but I set the aperture to f/8 and used live view for focus checking with the camera on a tripod, which I've read on forums is the proper thing to do before you take a picture.

And thankfully for this I didn't have to do any 25% math to find the corners, my camera does the math for me by putting up a 4x4 grid in live view.
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