Blotchiness Revisited?

[griz8791]

I asked about this here

https://www.nikoncafe.com/vforums/showthread.php?t=236378

and never got around to responding to Mike's suggestion to post a 100 percent crop, so I'm doing that now with a different photo:

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This is a 100 percent crop of a .NEF which I have opened in NX2, souped up a little with color control points (one of which is just to the left of the cloud in this crop) and then saved as a .jpg. No resizing other than the crop, and no sharpening. To me this seems regularly irregular (very small globs) and therefore likely to be noise.

Here's the same crop, converted to B&W. In this one I think I see little squares or rectangles rather than very small globs, which is why I wonder if it's a conversion artifact:

View attachment 388245

I have seen this same type of thing with previous B&W conversions of .mrw files taken with my Konica-Minolta A2. I used a polarizer in the image I'm putting up here and I also used a polarizer on all of the unsatisfactory B&W conversions with my K-M A2.

 

[griz8791]

I realize the crop looks terrible so I feel compelled to defend my gear and myself by supplying the uncropped image as well. This one, though uncropped, has been resized:

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[Mike Buckley]

griz,

Thanks for posting the entire image because it is nothing short of stunning. I love the way the highway leads my eye to the one cloud bank that drops to the horizon.

Just one critique that I just have to offer even though you didn't ask: straighten the image so the telephone pole closest to the right edge and the small pole close to the left edge are closer to parallel with the edge.

I'm confident that you should follow Jan's observation and suggestion from the earlier thread: it's posterization that can easily be fixed by applying noise reduction to the bothersome portion of the sky.

By the way, you might consider posting your real name, at least your first name, at the end of each post. I would be willing to bet that it's not griz.

 

[griz8791]

Thanks, Mike. It's a tough image to straighten. First I used the NX2 straighten tool on the closest power pole and that put the horizon out of whack. Then I used it on the horizon, beginning just inside the left edge and continuing along that ridgeline to just past where the road vanishes over the horizon. That got that horizon horizontal, so to speak, and as a bonus also seemed to put the second, third, and fourth power poles vertical or close to it.

I shot this with the 18-55 so part of it might be wide-angle distortion.

It's also possible that wind has blown that first power pole off vertical over time.

I will hit it with some selective noise reduction. Any ideas what might be causing the posterization?

John

 

[CharlesVincentPhotography]

Thats a great shot 'griz' :biggrin: i too just like Mike love the way my eyes caught the highway and just followed to the end where the clouds meet. I love the uncropped one, and in color too

 

[Mike Buckley]

John,

That's the type of image that I believe you need to manually use the Straighten Tool by typing various values by trial and error until the image looks good. Drawing the line created by the Tool won't work well for the reasons that you mention.

I don't know what creates the posterization. It wasn't that long ago that Retief taught me what it is and how to spell it. :biggrin: I only know how to fix it, thanks to the good folks that hang out around here.

Congratulations again on a wonderful image that is well worth the time required to perfect it.

 

[Palouse]

That's a Big Sky shot if there ever was on!!!!! NICE!

 

[daveg]

Griz,

When you are converting from NEF to JPEG what quality setting are you using?

If you are using Photoshop try using quality 12.

In NX2 set to MAXIMUM (Excellent Quality)?

DaveG

 

[Gaius]

Power Poles

In Montana the power poles are most certainly not always straight. I notice the highway is not exactly straight either -- I wonder if the wind moved that too! :biggrin:

 

[Gaius]

For those who have never been there, the wind does blow on the eastern side of the state. Trees often have a definite lean to the east. Just east of Marias Pass, trains have been derailed from wind gusts

 

[sylvesterii]

Give the auto distortion correction tool a shot in NX2 for the straightening. It might help. the 18-55 while a great lens does have some distortion issues.

Also, from what I understand posterization is caused by a lack of bit-depth (i.e. there just aren't enough "shades" available to render smoothly). Although there are millions of colors in reality, it is still less than what is truly out there.

Think about it this way. If you had only 6 colors, i.e. red, orange, yellow, green, blue, purple. Take a picture of the sunset. our eyes sees a very smooth transition. If you had to assign one of those six colors though to each pixel, it will run into trouble. Is it orange, or is it red? well, when it decides the color it is "seeing" it is closer to red, then it makes it a red pixel. when it decides the color it is "seeing" is closer to orange, it makes it an orange pixel. Thus there is a difference that becomes quite noticeable. Converting to .jpeg would also increase the difference, because you will be going from 14 (or likely 12 depending on how you set your camera) down to 8 bits.

When you apply color control points, this accentuates these differences because of the way the selection occurs. It selects based upon strength of color. Thus if it is slightly different than the "selected" color, it gets less of the effect, thus exagerating the difference and the posterization. It is one of the main reasons I don't actually like using color control points for skys. Much easier to paint in the effect. In fact, I don't actually use color control points at all. Although, selection control points would likely suffer the same issue, but perhaps a bit less so because it takes into account more things I think when it makes its "selection."

I am sure there is a lot more to it than that, but that was how I understand it.

 

[griz8791]

That's a great explanation, Jan.

I can tell I am going to have to fight the temptation to go nuts with the color control points. As soon as I drop one in and start dialing down the brightness the excitement gets the better part of judgment and I wind up taking it too far.

Can you explain a little more what you mean by "painting in the effect?"

 

[sylvesterii]

Can you explain a little more what you mean by "painting in the effect?"

Sure.

There are two ways to go about it, depending upon what works for your situation (usually how much or how little the effect you want to apply)

Let's say you have an image with about 30% sky, and you want to use noise reduction to smooth out the color issues. select a new adjustment step, but don't assign it to noise reduction yet (it takes a lot of horse power, so you can work faster without hang ups). Now, select the "+" selection brush, and go as large as you can and "paint" the sky. I generally will make it so the brush is set at a high opacity for this (likely 100 for this type of task) and a low brush hardness (likely around 0) What this will do is it will "fully" select the image in the midlle areas of the brush, and gradually reduce it towards the edges. This helps prevent any really harsh sharp edges that would become noticeable. Once you have the majority of the sky painted green, then make the brush smaller and get into the finer details. If you have an area that is really hard to get into, such as leaves and such, use a selection control point and try as you can. If you over paint, then use the - brush.

If the majority of the image is going to be selected, then do the opposite, use the - brush first. (this will select everything except where you paint.)

Once you have your selection in place, then you can apply the noise reduction and fiddle with the settings.

it is somewhat labor intensive, but probably the best approach if there is some major fixing needed.

You can always try using selection control points first, and then just paint in or out areas you do or don't want, or use negative selection control points to unselect areas. Although I have to say, it can just be as labor intensive or even more so to do it that way.

 

[sylvesterii]

Oh, and as far as for darkening skys or whatever, you would just use the tool that the color control point was used for. i.e. if you are darkening the sky, there are many ways to do that. LCH, Levels/Curves, Brightness, saturation etc. you may have to do more than one adjustment with the same selection. This can be acheived by holding down the shift key with the current step active when you select the adjustment from the drop down menu.

So that way, you can darken and blue up the sky, and then add noise reduction all with the same selection.

Alternatively you can copy the adjustment step, paste it, and then change the adjustment. That way the complex selection you just made will be replicated (too bad it can't be inverted, but that is a whole different thread). That might be the better route for the noise reduction step, because you could disable it until you are done since it does take a lot of processing power.

 

[Mike Buckley]

(too bad it can't be inverted, but that is a whole different thread).

Don't get me going on about THAT. :biggrin: