[Dave]

Having shot High key in a studio shoot, to achieve that perfect white background, it got me thinking Is it feasible with reasonable PhotoShop skills to add backgrounds at will ,thus saving need for numerous "actual" backgrounds , for the shoot ???

If so, any tips on how to process in Photoshop for realistic effect ??

[Lone Buggin]

Not sure on this. Maybe if you had a file of stock images taken from the same perspective that you would have taken them from if they'd actually been portraits. Then cut out the backdrop on the studio shot, and merge the two? I think maybe you could get an effect along the lines of this. Again though, just theory on my part.

[VinnyP]

You can get digital backgrouinds for just this purpose. The only thing is it's tricky to extract people especially hair from white backgrounds. I have a reversible Chromakey background then you can select by colour range and its a doddle.

[Les Meehan]

Dave

I see little problem with this idea as long as your selection skills are up to the task.

Or accept that selection can be done creatively like this and go for it...



Cheers

Les

[shipwack]

I suppose it all depends on the definition of "feasible", or maybe how valuable your time is...

I've dabbled in this a bit, and I've come to the conclusion that (at least for my skill level), it is faster/easier to have the desired background there in real life, rather than 'shop it in later.

Maybe those with better tools/skills can do it better or faster than I, though.

[Dave Canon]

Dave, I have often encouraged the use of plain backgrounds for that very reason. However, I have found selecting the model (or the background) to change the background has been successful in a few cases but it can be hard work. You do need to learn all the tricks if you are to successfully cut out hair etc. or possibly buy some super software to help do this. An alternative to changing the background entirely is just to change the colour of the background which may be a little easier.

If I have not put you off, I recommend that you stay in colour to do this even if you wish to end up with B&W. You can try making a mask from the subject itself. You may find that one of the RGB channels shows better discrimintion between subject and background. Use that channel as a starting point for the mask and build up the mask by increasing its contrast and filling in as necessary.

One further trick I have found - If the new background has some similarities to the old (e.g. changing one landscape to another which is similar), then you only need to roughly cut round the model but use feathering to make a gentle blend.

[GainfulShrimp]

I used to use Corel Knockout 2 for this type of thing, but sadly it seems to have been ignored/abandoned by Corel - they haven't updated it in years and the 'current' version doesn't work at all with recent versions of Photoshop. I wish they would bring it up to date as it was incredibly easy to use.

Anyway, on the plus-side, there's a book I'm planning to buy which is recommended quite often as the best book on masking techniques:

Photoshop Masking and Compositing by Katrin Eismann

VinnyP - I've read somewhere that chromakey style backgrounds are not necessary for doing digital backgrounds for stills (but they're very popular for automated processing used for video). Do you find they help with stills too, or do you use yours for video? Do you use specialist software to extract the subject from the image?

[VinnyP]

I have tried them for video but mostly I use them for them stills. As you say it is possible to extract from any background but it can be tricky. Chromakey backgrounds are so lurid that it's usually easy to find one where no other colour in the picture is even close. I don't use any special software, photoshop select by colour range usually grabs it in a second. It is so much easier.

[Dave]

Got any example end shots ?

[danpen]

I've found masking can be very time-consuming and difficult to do realistically. But there is a way of doing it quite quickly and with which I've had some great results.

It requires you to add the new background on a layer over the original image and uses the darken blending mode to display the new background where it is darker than the original, while displaying the original image where it is darker than the new background. You can than add a layer mask to fine tune the results.

1. Get a nice white background to the original shot
2. Get your replacement background onto a new layer, make sure it's darker than the original background and lighter than the subjects
   • Backgrounds can be generated quickly using a new layer, the Render Clouds Filter and some Gaussian Blur, lighting effects can be applied with good effect too.
3. Set your new layer's blending mode to darken, if you got the tones right in step 2. this should be around 90% there.
4. Add a layer mask and using a soft brush paint black or white to tune the results
5. Sometimes it's worth putting a small Gaussian Blur on the Layer Mask (radius .5 - 1 pixels) to soften the edges.

The important thing with this approach is that it's non-destructive, you can keep tuning the layer mask and the opacity of the layer until you get an effect you like.

cheers

Dan

[VinnyP]

Originally Posted by Dave

Got any example end shots ?

Sorry nearly missed this assuming it was for me. I have but would need to check with the subjects. What I will do is shoot something and the process in the next week or so and, time permitting ,try to knock up one of those tutorial things.

[GainfulShrimp]

That would be brilliant Vinny, if you don't mind. I'd also be very interested in seeing that.

Saying that... I had a crap day at work yesterday and hence did some retail therapy - ordered myself a chromakey background and that Katrin Eismann book I mentioned, so looking forward to giving it a go when I've got some time over Christmas.