Digital ND Grad Filter

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Digital ND Grad Filter

Postby Bob G on Mon Jun 19, 2006 4:14 pm

A while ago I posted a sunset pic taken from the O'Reillys Minimeet.

It was a blend of several pics taken at different exposures and merged in photoshop using the HDR function. This looked a bit artificial and your comments reflected that view.

I have had another attempt using the Digital ND Filter technique as described by Fred Miranda on his site and copied below for anyone interested.

Here is the O'Reillys sunset photo revisited with this much simpler tecnique and in my view the better.

Would appreciate any comments

Digital ND Grad
Image

HDR Merge
Image

Here are the steps for Digital ND Grad filter:

1) Take two pictures. One picture should be well exposed to the foreground, with the background overexposed. For example, if your background is a bright sky, the sky will appear overexposed since you've exposed for the foreground. Let's call this first image "Overexposed".

Then, for the second shot, do the exact opposite. This time your foreground will appear "underexposed", and your background well exposed.

2) Bring both images into Photoshop. Make sure you convert them to 8-bit mode.

3) Drag the overexposed picture on top of the underexposed one, while holding the SHIFT key. This will place them into 2 perfectly aligned layers.

4) Make a layer mask for the "overexposed" image by clicking on the layer mask icon at the bottom of the layers palette.

5) Click on the layer mask to make it active, and then select the linear gradient tool.

6) Drag a line from the top of the image toward the bottom until you reach the part of the image that it's not overexposed

The gradient you just created on the layer mask is the "digital split density filter". Now you can control the intensity of the effect by using the "Opacity" slider.

*Note: Raw shooters only need 1 RAW file converted to 2 images. First convert your RAW file into a non-linear image (overexposed). Next, convert the same file to a linear image (underexposed). Then, follow the same steps. Place the underexposed image on the bottom layer and the overexposed image on the top layer. For the non-linear file, use "High" contrast when converting the RAW file.

So, the next time you are out there shooting, if you accidentally forget your gradual filter -- don't panic. Now you have a new technique to help you save those once lost images.


Bob G
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Postby moggy on Mon Jun 19, 2006 4:24 pm

Works for me Bob, I must give this technique a try, thanks for the heads up. :wink:

8) Bob.

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Postby greencardigan on Mon Jun 19, 2006 4:34 pm

Sound good.

It looks much better than the HDR Merge.
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Postby DJXtreme on Mon Jun 19, 2006 4:43 pm

fantastic looks heaps better than the HDR merge and whats more steps so easy even i could follow them!
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Postby Bob G on Mon Jun 19, 2006 7:00 pm

Pleased you agree - now all I have to do is get it to print as I want it.

Pigment inks are great but the colour gamut is not as good as the dye based inks.

I am going to bite the bullet and callibrate my monitor and have a few profiles done for my Epson 2400 with Epson Archival Matte and also with Hanemuhle Rag.

Why didn't someone tell me this photography hobby was a neverending pursuit of obstacles and achievement and change and compromise and expense

:lol:

Bob G

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Postby johnd on Tue Jun 20, 2006 1:36 pm

Absolutely no doubt about it Bob. The digital ND grad has worked far better than HDR. A great tip.
Cheers
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Postby Willy wombat on Tue Jun 20, 2006 4:30 pm

Great tip and the results looks striking.

Cheers - i will have to try the "Bob G" technique
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Postby Colcam on Wed Jun 21, 2006 7:49 pm

Very nice indeed Bob. The ND image is really subtle and has good range. It looks like it is straight out of Tolkein. I will make a note of the steps you gave and give it a go.
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Postby SteveGriffin on Wed Jun 21, 2006 8:21 pm

That is a great tip Bob
I used it on the 1st shot below to get the 2nd which I think is a much more acceptable result
Image Image
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Postby Bob G on Thu Jun 22, 2006 10:16 pm

Thanks for posting those Steve - that is a great example of using the Digital ND Grad tecnique. I probably wouldnt have even thought of using it in this shot. - Well done

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Postby SteveGriffin on Fri Jun 23, 2006 6:17 am

It certainly made a big improvement to the shot.

I had a wedding in the ballon last Saturday and gave a number of the shots a similar treatment. A couple of them will probably appear in the Sunday Mail this week or next in a feature on unusual weddings.
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