Blending shots in Photoshop (CS6)

[Gromit44]

Can anyone think of a technique for blending these night exposures in Photoshop CS6?
 
I’ve got a range of tripod shots of an old 16th century building, with exposures going from -1.7ev to +1.7ev. Small sections of two of them are shown below.
 
The first (2994) is correctly exposed for the light bulbs but the building itself is underexposed. The second (2997) is correctly exposed for the building but the light bulb areas are completely blown out.
 
I’m trying to blend them together so that the building and the bulbs are both correctly exposed throughout. The problem is my Photoshop skills are limited and I can’t find a way of doing it without the edges of the layer mask becoming visible - i.e. if I apply it to the light bulb areas, it also darkens the walls behind (third pic below shows this effect - I’ve exaggerated it to illustrate the problem).
 
Does anyone have any bright ideas? (pun intended ☺). Maybe there’s a way of creating an ‘auto mask’ to replace just the areas that are over a certain level (i.e. the bulbs).

[Gromit44]

BTW, I've tried HDR (using both Merge to HDR Pro and HDR Efex Pro) and can't get a result that looks realistic.

[Gromit44]

BTW2, feathering the mask in CS6 is the best I've managed to come up with.

[Hayo Baan]

Hi Simon,

This is normally exactly what HDR processing is for. While perhaps a bit limited compared to say HDR Efex Pro and PhotoMatix (full blown HDR processors), Photoshop's own blending can still be used to good effect. You find Photoshop's HDR mode under File|Automate|Merge to HDR Pro…

After blending your images into a 32-bit image, should tonemap it to a 16 or 8-bit image. There are various methods/settings for this, ranging from natural/realistic to arty/unrealistic. Pick the one you like best and adjust (if necessary). As you mentioned, however, you can't seem to get a realistic looking result from either software. Perhaps I can have a go (if you could e-mail me the raw files, that would be best).

If you want to do it with masking, I'd try to make use of the blend if sliders (right click the layer in the layers panel and choose Blending Options…) to have Photoshop automask the brightest spots of the “bright” version of the image, revealing the darker version. Of course manual masking/feathering would also work (but is likely much harder to achieve).

Hope this helps,
Hayo

[Gromit44]

Perhaps I can have a go (if you could e-mail me the raw files, that would be best).

The NEFs are 74MB each - my email attachment limit is a pathetic 6MB.

If you want to do it with masking, I'd try to make use of the blend if sliders (right click the layer in the layers panel and choose Blending Options…) to have Photoshop automask the brightest spots of the “bright” version of the image, revealing the darker version.

I don't know how to use the 'Blend If' sliders. Nothing seems to happen. 

[Hayo Baan]

Perhaps I can have a go (if you could e-mail me the raw files, that would be best).

The NEFs are 74MB each - my email attachment limit is a pathetic 6MB.

Ah, you're right: D800 files are huge. But I also guess you shot uncompressed NEF then. You probably have your reasons for this. but why didn't you choose lossless compressed? That saves a ton of space without loss of quality.

If you want to do it with masking, I'd try to make use of the blend if sliders (right click the layer in the layers panel and choose Blending Options…) to have Photoshop automask the brightest spots of the “bright” version of the image, revealing the darker version.

I don't know how to use the 'Blend If' sliders. Nothing seems to happen. 

Are you trying this on the top layer of the two image layers? If you mail me two small jpg versions of the files, I can try it out for you to see if it works as I expect.

[Gromit44]

I always use NEF uncompressed. I've found using lossless compressed only saves around 20-30% on average and I'm not worried about drive space, so I may as well keep all the available data.

The JPEGs are 11-21MB (JPEG Fine) so they're still too big to email. I'll have to reduce them quite a bit to get under the 6MB attachment limit. Will <6MB be good enough for testing?

[Gromit44]

Are you trying this on the top layer of the two image layers?

Which is the top layer - the dark one (light bulbs) or the light one (building)?

[Hayo Baan]

I always use NEF uncompressed. I've found using lossless compressed only saves around 20-30% on average and I'm not worried about drive space, so I may as well keep all the available data.

Lossless compression IS lossless. The compressed option (without the lossless prefix) is the lossy version. On average I'd say the space savings is about 40%, especially with those d800 files, worth making use of (IMHO)

The JPEGs are 11-21MB (JPEG Fine) so they're still too big to email. I'll have to reduce them quite a bit to get under the 6MB attachment limit. Will <6MB be good enough for testing?

I only need a small say 600-800 pixel sample to try.

Which is the top layer - the dark one (light bulbs) or the light one (building)?

The top one is whichever of the two images you put on top of the other in the layers panel

[Gromit44]

I only need a small say 600-800 pixel sample to try.

OK, I'll email small JPEG sections cropped from the NEFs (using NX2's batch process to make sure the crops are identical).

[Hayo Baan]

While I couldn't easily get a really good looking result with just the blend if sliders, I also tried loading your three images into HDR Efex Pro 2. By only modifying exposure (-30%) and highlights (-50%) from the defaults, I think I got a fairly natural looking result. With further tweaking you will likely be able to improve the result even more.

Attached is my quick go at it.

[Hayo Baan]

While I couldn't easily get a really good looking result with just the blend if sliders, I also tried loading your three images into HDR Efex Pro 2. By only modifying exposure (-30%) and highlights (-50%) from the defaults, I think I got a fairly natural looking result. With further tweaking you will likely be able to improve the result even more.

Attached is my quick go at it.

Thinking about this and looking at your samples, I actually think there is a lot that can be done using shadow/highlight recovery on the raw files in either Capture NX2 or Adobe Camera Raw (Photoshop). This way you will likely only need one of the exposures (likely the middle one) to come up with a good looking result. Especially with the awesome dynamic range of the D800, I think this is doable.

Cheers,
Hayo

[Gromit44]

While I couldn't easily get a really good looking result with just the blend if sliders, I also tried loading your three images into HDR Efex Pro 2. By only modifying exposure (-30%) and highlights (-50%) from the defaults, I think I got a fairly natural looking result. With further tweaking you will likely be able to improve the result even more.

Attached is my quick go at it.

Did you set the ev values (-1.7, 0 and +1.3) on the screen before HDR Efex Pro actually launches? I'm getting this:

[Gromit44]

While I couldn't easily get a really good looking result with just the blend if sliders, I also tried loading your three images into HDR Efex Pro 2. By only modifying exposure (-30%) and highlights (-50%) from the defaults, I think I got a fairly natural looking result. With further tweaking you will likely be able to improve the result even more.

Attached is my quick go at it.

Did you set the ev values (-1.7, 0 and +1.3) on the screen before HDR Efex Pro actually launches? I'm getting this:

If I set them to (-1.7, 0, +1.3) I can't duplicate what you did. Which preset did you use?

Here's what I get.

[Hayo Baan]

Did you set the ev values (-1.7, 0 and +1.3) on the screen before HDR Efex Pro actually launches? I'm getting this:

Yes, I got the correct exposure information. If you're not getting that, something is off. What version of HDR Efex Pro are you using? Version 2.x or an older version? Standalone or the plugin (that's what I used, started from Adobe Bridge).

If I set them to (-1.7, 0, +1.3) I can't duplicate what you did. Which preset did you use?

Here's what I get.

Weird. I didn't use any of the presets, just the defaults.

For best results by the way, it is best you use tiffs (16 bit) in e.g. ProPhoto RGB.