I understand your questions, its really hard to match the realism of a subject/photo, but some of my techniques i used was very light opacity about 13% of my brush, normally i use blur brush, the normal brush. Working in a high resolution like 4000px about 200-300 dpi. In realism you need a lot of patience.
I also discovered recently a realistic effect you can find my output here [link] but i cant tell this for the moment. The Final work link is here [link]. You can also browse some of my past works
i use the low opacity of brush for 1st touch and retouching it again and againt until i get the right shade, both small details and big as Shades. I zoomed it too for very detailed section.
your other problem was the lighting? i have somes technique like using Soft Round Brush and Burn Brush. You can also save as it or create a JPG and add layers and start experimenting on the shadows/shades.
this is not too much detail but you can see my process:
I see, thats my common used brush but I also use diff brushes depending on the texture i want but still using low opacity, it helps me a lot. My final touch of the skin was overlayed by skin texture so the airbrush effect will gone.
Ok, thats the common problem of lighting. I think you just need more practice for realism.
It sounds like it is about textures rather than faces. Practicing drawing things with different textures really helped me. Whatever you can find just pile it up and try and describe it with whatever you have. Try and represent the different surfaces and move around it and look how the lighting works and stuff.
Then go back to your faces and try and find uses for the techniques you have tried. At least some of it will come in useful!
I don't know. If you are thinking you can add textures at the end as an afterthought then then you are thinking about something very different to me.
I'm talking about bumps and lumps and creases and folds. The difference between things that are stretched and smooth and things that might be sagging and wrinkly. To me different textures and surfaces are something quite integral to a picture rather than something to be tagged on at the end - although it may just be me that is clueless.
Just finding a flat picture of someone with a wrinkly face and trying to apply that to your character won't necessarily work - those 2D featires created from their specific lighting can't necessarily be 'copy and pasted' to another image. In my experience if you can find a nice wrinkly vegetable and study it from different angles you can get a much better idea of how the creases work with different light sources and how tissue might sag and so on and so forth. And if you practice drawing it you can soon find short cuts that get nice effects that you can apply to a more 'interesting' face.
But it's not like I'm an expert or anything, so whatever...
I'm a self-taught artist so I may well have the wrong attitude or mentality! To me the texture is the surface that I'm trying to represent on the page - either actual paper or a digital 'page'. I'm trying to represent either a bump a crease or a freckle or a birthmark with the marks that I'm making on that page. Physically they might be different things on the object that I'm trying to represent - but that they should be treated differently in the drawing process, some as marks that I can add on afterwards and some that I shouldn't, seems really weird to me.
You are trying to represent a 3D object using a 2D medium. Personally I think it is important to keep those two concepts seperate - but whether a specific feature might be a 3D fold or a surface blemish you are trying to represent them using the same tools. If that makes any sense?
I like gardening and I grow plenty of wrinkly vegetables, such as my parsnips. Maybe I'm doing that wrong too!
For the purposes though an interesting sculpture would be at least as good as a vegetable!
I did a lot of stuff with inks while I was learning my 'art'. I would sketch my structure with pencils - the skull for a portrait or whatever. Then I would work on the most distinctive features like creases and blemishes and deep shadows with waterproof indelible inks. I would start shading and try and make different textures using different kinds of pen strokes. Then I would splash water soluble ink washes or watercolours around on top of the waterproof inks to build up tones and colours.
Even now I'm trying to paint digitally I work that way round. The sketch, then significant details, then the broader shadows and colours. Which seems to be the opposite way to what you have described!
But either way I think the difference betwen a rough texture and wrinkles or folds is a matter of scale rather than a different process. You are simply trying to represent those surfaces with the marks you can make but mistakes with lighting and so on will be more obvious on a bigger scale. If you have practised drawing actual wrinkles from different angles and different lighting then you have a better chance of getting a result that matches to the rest of your picture and looks realistic. I think. Hopefully...
In any event, I think if you can draw a parsnip and if you can imagine wrinkly people as being made up of multiple parsnips then that may well be the way forward. And if not then you can eat your parsnips with a honey glaze and they will be really tasty!