Lesson learned - do not over sharpen

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LVF
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Location: Sequim, Washington

Lesson learned - do not over sharpen

Post by LVF »

This post is for beginners, like myself, who are learning how to do photo stacking. If you sharpen your final photo stack, take care to watch for out-of-focus areas, they get over sharpened and give strange looking artifacts.

I posted a final photo stack of a bouquet flowers and posted the results on May 17. I had sharpened the final photo stack in Camera Raw CS6 at 100% view and thought I was getting a nice sharp photo - I couldn't have been more wrong.

Here is a few quotes as to why the photo was over sharpened:

Rik - "Your images look like they are being seen through rippled glass."

JohnyM - "It still looks like oil painting to me, rather than photo."

JohnyM - "Honestly, i see nothing sharp about them. Can you point the sharp parts that you have in mind, with arrows? "

Rik - "The difficulty is that your "very sharp petal edges" are now appearing to quite possibly be artifacts, strongly modified by whatever process is causing the strange textures."

Obviously I did something wrong. So I decided to look closely where I went wrong in processing the final photo stack.

Here is the photo of the of the stack that I posted May 17:

Image

Here is the 300% view of a small area of the upper right area of the photo, that Rik showed me, that illustrated the problem with the photo:

Image

The photo definitely has the problem as sited by JohnyM and Rik.

I looked at other areas of the photo at 300%, and saw the same problem. Some areas of the photo did not appear to exhibit as much a problem on the edges of petals and flowers, but did show the problem within the petals and flowers:

Image

Image

Image

Image

I obviously over sharpened the photo.

I decided to do the 8 photo stack again and do zero sharpening of the final stacked photo, Here is the non-sharpened stacked photo:

Image

Here is the area that Rik examined at 300%, and pointed out the problem:

Image

It shows that that area is out-of-focus and my sharpening gave this:

Image

The problem boils down to two things:

1 - I did not take enough photos, to make the final stack, to eliminate out-of-focus areas, and

2 - I over sharpened.

This has been quite a lesson for me. I have learned a lot from this posting. I started stacking a couple of weeks ago and got overly enthusiastic with my results.

I jumped in and started posting in this professional forum thinking I was doing pretty good. But Rik and JohnyM opened my eyes.

As a final investigation, JohnyM said that the "background in the photo was very distracting". He went on to say that he uses Gaussian Blur a couple of times on the backgrounds in his photos. This inferred that if I used Gaussian Blur a couple of times it would improve my photo.

What JohnyM sees in my photo that he finds distracting, is the background fabric weave and two folds in the fabric that produces two dark areas in the background. I was not paying attention to the background in my processing but I will do so now.

I used Gaussian Blur in Photoshop CS6, on the background of my photo.

I did it once at 25% with no improvement - still dark areas. Did it again at 25%, again dark areas. Finally, I really went at it with 100%, and still there was not what should be a nice uniform out-of-focus background.

Here is what I got after three Gaussian blurs:

Image

I still see the two dark areas that distracted JohnyM.

So I started over with the stacked photo, and simply selected the background and, in one step, replaced it with a uniform background:

Image

I find this background much more pleasing and I did not have to use Gaussian blur.

I have said enough about this problem. I will continue to learn photographic stacking but not post until it is up to your forum standards.

Thank you for the lessons learned.

Leon

JohnyM
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Post by JohnyM »

Dont take things so personally. I think you've already made big progress in post-processing.

Non-sharpened image looks much more natural and pleasing to me.

Gausian blur is not used to remove something from the picture, just to smooth it out. In example, i marked distracting backgrond patches in your original photo:Image
And fixed it with fast mask and gausian blur (quick and sloppy, just for demonstration):
Image
You could also do that with retouching in stacking program.

You completely removed background, which also works fine in this case. But if you make shots of flowers in the field, with lots of grass behind, gausian blur /retouch is your only way to go. Also, you still missed one spot in bottom left corner (between leafes).

ChrisR
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Post by ChrisR »

Interesting narrative, Leon.
I think you got some pebble-glass effect because the original image noise was getting sharpened. You used ISO 800, so there was scope for lower noise. Stackers use base ISO whenever they can, because the noise gets seen as detail and retained. (That's more noticeable in some image stacking methods than others.)
You weren't getting the classic over-sharpening effect on the flowers detail itself.
Image
Chris R

Ultima_Gaina
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Post by Ultima_Gaina »

This begs another question about sharpening, when shooting RAW:

I believe it is better to set RAW sharpening (i.e. in Lightroom) down to zero before stacking, to minimize stacking artifacts, and only mildly sharpen the final, retouched and post-processed TIFF, before JPEG conversion.


Do you have a different opinion/experience/workflow?
And if yes, why? In other words, is Zerene expected to work better with "some" RAW sharpening, or not?

rjlittlefield
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Post by rjlittlefield »

Ultima_Gaina wrote:In other words, is Zerene expected to work better with "some" RAW sharpening, or not?
My standard recommendation is to do some sharpening and noise reduction before stacking, with the aim of enhancing real detail while pushing down random noise.

Improving the "signal-to-noise ratio" will improve the software's ability to make correct decisions.

But appropriate settings depend heavily on what the subject is and how it was shot, so unfortunately I can't give any numerical guidelines about what the settings should be.

The best I can say is to look carefully at the source image and think about that distinction between real detail and random noise. You want to push up the detail while pushing down the noise. The ripply textures that we've been discussing in Leon's images are good examples of what you do not want a stacking program to see, because it won't be able to distinguish between the sharp ripples caused by random noise and whatever real details there may be in the image.

--Rik

Lou Jost
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Post by Lou Jost »

I will continue to learn photographic stacking but not post until it is up to your forum standards.


Leon, many of us (myself included) are beginners, and all of us started off as beginners. Sharing our trials and errors as well as our successes is part of the learning process, and helps others avoid the same mistakes. So speaking for myself, I hope you will not be shy about posting as you learn new things.

LVF
Posts: 66
Joined: Sun Apr 23, 2017 4:17 pm
Location: Sequim, Washington

Lou Jost

Post by LVF »

Thank you for your encouragement to continue posting. So, I just posted a fun time playing around with my photographic gear.

Leon

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