That all depends on how you view "photography" as a field.
If you are in journalistic photography field, adding or subtracting elements of photography is considered immoral and unethical. Journalistic photographs are supposed to reflect the reality as situations happened.
If you are in artistic photography field, photograph is a medium you use to express your emotions and solicit emotions. As such, any modification is perfectly permissible, just as painters never paints as they see the scene.
As to using lighting in studios, they don't add or subtract anything from the scene. Lighting renders subjects differently. Here, you have to define what you mean by "alter" the image.
Let me give you an example:
Portrait photography is my field. Outdoors or indoors, at studio with strobes or outside with sun and shadows, I place subjects where I want them, orient them, and pose them so lights fall just right and shadows are where I want them to be and at the right degree.
If I am photographing a subject with an obvious defect (that client wants not seen) or an overly obese person, I try to position them, light them, and render them so that the resulting photograph will look the way the subject wants to be viewed. You'd be amazed what's possible.
Now, is any of this "alteration?" Is any of this "non-real"? No, it's just part of photography. Present the subject the best way possible.
After the fact, I may edit few distracting background elements that I couldn't move, or remove skin blemishes that are obvious. How far is too far? Who to say what's too much? Here, I'm trying to draw positive emotional responses but some may see this as negative. Who knows. Better yet, who cares? Do you? Do I? Do my client? Do clients' friend? Does it matter for the purpose of this photograph?
Here we’ve focused on three basic setups which will be more than enough to get you going, but the sky’s the limit even with just two heads.
It’s always a good idea to ‘build’ your lighting. Start with your main light and once that’s in the right position introduce the next light and then position your reflectors. The height, angle, power and distance of your lights will have a dramatic impact on the shape of your subject’s face, not to mention whether you use a naked flashbulb, a soft box, a snoot or an umbrella.
Nearly all studio kits come with modelling lights and it’s vital that you keep these on so you can see how the light is falling on your subject. Use your camera’s LCD screen too; sometimes switching to monochromatic preview mode can help you concentrate on shape, tones and shadows falling on the face and pre visualise the end result.
How to set up studio lighting: 01 High
In most cases you’ll want to have your main light positioned above the model. Notice how the shadow from the nose falls down the face, elongating the features. Ideally you want the shadow of the nose to point towards the end of the lips. The triangle of light on the cheek on the shadow side is often referred to as ‘Rembrandt’ lighting; get your model to move their head slightly to achieve this.
How to set up studio lighting: 02 Eye level
With the flashlight to the side and at the same height as the model the light falls across the face, causing a shadow that widens the facial features. If this light is balanced with one of equal strength on the other side it can be quite effective, but as a sculpting technique height would be better. Keep your flashlight’s modelling lights switched on so you can see how the shadows will lie.
How to set up studio lighting: 03 Low
There are unlikely to be too many situations when a low light is going to work well as your primary light source. It gives a spooky look, so Halloween is probably the only time you’re even going to think about using this technique. As you can see from our example, underlighting is not very flattering even on a young model. With under lighting the nose shadow is clumpy and any bags under the eyes will be amplified.
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