Monday, February 1, 2010

Post Processing in my Food Photography

I'm frequently asked, if I do post process my digital photos. Of cause I do! It is part of the whole photography process. For me "post processing" is the part which is comparable to "film development & print" in analog photography. Post processing is the fine tuning in digital food photography and for me integral part of it.

In the following I will give a brief overview about the post processing steps in my photography.

White Balance / Color Balance
Although I check the white balance frequently throughout a shooting using a grey card and manual white balance of my camera, there are cases where a little correction is needed or where I would like to emphasize a certain color mood.
I check every of my photos for white balance, even if the white balance doesn't need to be adjusted. It has become a routine operation for me in post processing. And with that routine I have trained over time my eye for slight variations in color mood, color hues and white balance.
To do this properly a color calibrated monitor is essential. A detailed thread on this topic can be found in the Food Photography Club of Flickr (Tips, Tricks & Opinions: Monitor Calibration).
A good white balance is always based on a proper setting of the white balance of your camera. When you have a digital SLR use the manual setting(s) and follow the manual. For manual white balance you will need a grey card (or when you don't have one a white sheet of paper instead) as reference for the manual white balance setting. If you don't have a digital SLR or your camera is just offering some pre-settings, use the one which comes closest to a neutal white. If you can't decide which setting works best on the little LCD screen of your camera, try different pre-settings. So you have different choices for the post processing later. For post processing it is very helpful to have something "white" in the photo as reference for your white balance adjustments. I often have used a very small piece of white paper and placed it somewhere in the photo where I could easily clone it out later after I have adjusted the white balance.
If you are interested in some more information, I suggest the following links:

A properly focussed photo is the basis of a good photo. With "sharpening" or "re-sharpening" I do not mean to sharpen an otherwise blurry photo and to repair it in some way. I would suggest to do it the hard way: DELETE every blurry photo. The worst thing that could happen to me is to rouine a good composition by wrong focussing and to get a blurry photo.

With a perfect focussed photo you can go into the further steps of post processing which are doing more or less the same as you know them from analog photography when you develop your films or doing prints in the darkroom. I don't want to get in the more technical details here, but in film photography the chemical processes involved enhance the sharpness of photos. A phenomenon which is often described as "unsharp maskening" and makes use of differences in toning of neighbour areas of your negative or during print development. Software products like photoshop are offering a digital tool to mimic this effect called unsharp maskening. It can be found in the filter section under the different sharpening tools.
For food photography I like the tool "highpass filter" often more, because it seems to enhance the overall contrasts and dimensionality of the photo. Especially for photos, where you need just a slight sharpening this works great. You will find it in the filter section under other filters.
In photos where I have large colored areas which should not be sharpened and other areas with fine structures which should be sharpened I also use the unsharp maskening method in the luminance channel of the photo. For this you have to switch from RGB-mode to the LAB-mode first. Then select the LAB-brigthness from channel section of your photo. After doing this you use a slight soft-focus of a- and b-channels (Gauss effect). With that you get good defintion in the fine structures without sharpening the colored areas too much.
For my post processing I often use the high pass filter with a pixel radius less than 5. The luminance method is more complex and you need some more fine tuning here. I often start with a setting for the unsharp maskening of the luminance of pixel radius of 1.0, a strength of 200% and a threshold of 2. For the soft-focus effect according to Gauss I start with 0.5 pixel radius for a- and b-channel.

Although I have used the expression sharpening in this section, one has the say, that it is not a sharpening (in the wordest true sense) but a method to enhance the contrast in your photo so that they appear "sharper". What I have said so far is based on my experiences for digital uses. For hard print you could use the same tools, but the tools are used differently.

Is there a case, where sharpening of a photo is a must? Yes. Any time you reduce image size in pixels or reduce data to make image smaller in storage size, you should re-resharpen your photos to maintain their status in sharpness. All my photos of medium size I posted here or on flickr are re-sharpened after size reduction.

Sometimes, when I have overseen a mark, fleck or stain, I try to clone it out. I have to admit, that I do this only for very small areas, where it can easily be done. The reason: I'm too lazy to spend too much time for this kind of post processing. And you can do it much easier, when you plan your shooting and do the arrangements very carefully. But accidents can happen and when it can easily be done, I do it.

Sometimes I play around with contrasts, gamma values or color saturations. But I have to say, that I don't use them frequently. Or when I use them I use them very carefully. Changes to the original levels seldom exceed 5%. And when I used them in post processing a variation in contrast, gamma values or saturation was part of the whole process. Example: When I would like to have enhanced contrast but can not get the effect by lighting, exposure and aperture I take into account if I could get that effect by post processing.

Gereneral discussions on post processing
Here are two links to threads on post processing you might be interested in to read:


Manggy said...

Thanks for the tips, TK! I actually started a second blog to address some of these techniques. I may not be the best at them but I think I teach pretty well :)

Lisa@ The Cutting Edge of Ordinary said...

Great tips! Thanks so much. I really learned a lot. Love the tip about the white paper! Genuis! Thanks again.

Thorsten said...

Thank you both for your feedback

Reds said...

Awesome post Thorsten - printing as I type - will be reading this thoroughly tonight!!

Mowie @ Mowielicious said...

Thanks so much for this great post Thorsten - very informative and helpful.

Thorsten said...

Thanks Redsie and Mowie

Sari said...

Thank you for those tips Thorsten. It's always very interesting to see the different approaches to post processing! I definitely agree that post processing is a must in digital photography, especially when you shoot RAW.

Sunshinemom said...

Thanks a lot for this post. I do not do much post processing because my photoshop knowledge is pretty low and I haven't given much time on learning the tools. Next time I open a picture in photoshop I will also keep this page open and check up what I do!

I would also appreciate if could cover a post on taking 'food pictures' in low lit conditions such as early mornings? That would be extremely helpful.


Thorsten said...

Yes Sari, when you shoot RAW you have to post process. As m ycamera do both formats (RAW and JPG) at the same time, I have the chance to use the JPG when I'm too lazy.

Sunshinemom, most of the tools you need will get routine after a short while.

Helene said...

I'm still in the process of learning. I love the idea of using white paper. I will try it. Thanks so much.

Walter said...

If I remembered it correctly, when shooting RAW, it gives more freedom in post-processing the image due having more parameters to easily editing the image, compared to JPG, with the cost of higher file size. But if there isn't much problem in shooting a lot, it would be good to use JPG instead. Other than that, I am amazed in viewing various images of food, due to its presentation and looking like it has came to life. Preparation-wise, it is different from shooting people, because you have to keep in mind in how to make them appealing in the eyes of the viewer and the other photographer. Irving where I currently live has a lot of photo enthusiasts that are giving me knowledge in photography.