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I have installed Sky HDR and Smooth Reflections on both of my cameras (A7RII and RX1RII). They replace GND and ND filters and output a single RAW file as result.
Sky HDR: This app replaces Gradual ND filters.
Basically it lets you set one exposure for the "land" and another for the "sky". A graduated ND filter (similar to what Lightroom offers) allows you to position the transition zone (up/down/rotate) and how hard/soft the transition is.
You can also choose different WB, ISO, Exp. comp. and aperture for land and sky.
An unique feature of the app is letting you set different apertures for land and sky. So, you may choose f/22 for the sky and f/8 for the land with a possibility of better sun stars combined in one RAW file. (Yes, you read this right. RAW!)
This works even with the RX1RII but you can't use the aperture ring. To set aperture you must use Av mode and use the rear dial instead.
With legacy lenses and even the Loxia line, the aperture ring works but you can't see one aperture for the land and another for the sky. Bummer.
Once you are set, the camera will take 2 pictures (a self-timer is included) and merge in camera. After merging, you still have a choice to tweak the results further before saving the RAW file.
Smooth Reflection: This app replaces ND filters.
Basically the technique used on the app stacks all images using mean blending. Astrophotographers have been using this concept for years to combine multiple photos of dim objects in the night sky to reduce the noise. That is one of the benefits.
Instead of using the app, you could do it in Photoshop:
Open each of the images in your stack as layers.
Align them (Edit → Auto-Align Layers…). Auto should work fine here.
Select all of the layers and turn them into a Smart Object (Convert to Smart Object).
Now apply the Mean Stack mode (Layer → Smart Objects → Stack Mode → Mean).
The issue here is that you may need 32 images to mimic a 5-stop ND filter and even more for more blurring. Mimicking a big stop is almost unpractical.
So, storing all these exposures in camera, bringing them to LR, exporting to Photoshop and running the above steps is very time consuming. That is where the app starts to sound interesting. It combines the images in-camera and the results are very similar. All you end up with is ONE RAW file. The downside is that the app does not align the images so you MUST have a very sturdy tripod and stable floor.
From my calculations here are the number of images needed to match the equiv. ND filters:
- 1 stop (2 shots)
- 2 stops (4 shots)
- 3 stops (8 shots)
- 4 stops (16 shots)
- 5 stops (32 shots)
- 6 stops (64 shots)
- 7 stops (128 shots)
- 8 stops (256 shots)
If you play with the app, avoid using any presets. Go straight to "custom", press menu and choose "Smoothing". There you will be able to select the number of shots you need. Also make sure to set the file to "RAW".
Another benefit from this technique is a significant improvement of signal to noise ratio.
If you "mean" average 4 photos, you'll have 1/2 the noise (technically S/N, signal to noise ratio). 100 photos will be 1/10 the noise. (Imagine how clean your final image will be).
I will post examples from both apps on this thread. Post yours as well!
BTW: For those using the App to complement their filters here is a quick table:
Starting with a 3-stop filter:
- 4 stops (2 shots)
- 5 stops (4 shots)
- 6 stops (8 shots)
- 7 stops (16 shots)
- 8 stops (32 shots)
Starting with a 6-stop filter:
- 7 stops (2 shots)
- 8 stops (4 shots)
- 9 stops (8 shots)
- 10 stops (16 shots)
- 11 stops (32 shots)