Archive for July, 2015

  • Techniques

    Photographing Artwork

     

    Note:  In the following photographs I only used the most basic lighting setups.  Even using natural light, you can take advantage of reflectors to highlight shadows and produce fill light.  Try searching “product photography lighting” if you are looking for information about advanced lighting.

    Natural Lighting

    The PBS Art21 documentary episode “Memory” contains a segment about Japanese photographer Hiroshi Sugimoto.  Sugimoto gives a tour of his photography studio which is surprisingly simple.  No fancy lights.  Just a camera, table, and backdrop placed near his studio window.  Sugimoto controls the lighting simply by rolling the window shade up and down.

    If you are not worried about lighting consistency from photograph to photograph, taking pictures of your artwork using natural light is the simplest approach.  You can wait for a cloudy day and shoot outside for diffuse, cool light, or use window light.  If you do not want a color cast, simply use a grey card.

     

    Simple natural lighting setup

    Grey cards

    Grey cards provide you with a reference neutral grey.  This grey can be used in photo editing software like Photoshop and Lightroom to correct for color temperature casts.  The grey card I use is X-rite ColorChecker Grayscale because it also provides a white and black reference which helps adjusting exposure and black/white levels.

    You might be tempted to use a sheet of paper, piece of styrofoam, or other object as a cheap reference with which to set white balance.  But in my experience, it’s much better to buy a professional grey scale card.  Even with something as “standard” as a piece of paper, the color differs between brands and thicknesses.

    Below are three photos taken with the same lens, ISO, white balance setting (Auto), shutter, and speed.  In Lightroom I only adjusted the white balance.

    Remember there is no “correct” color temperature.  You may prefer the cool window light, or the golden tones of late afternoon light.  The grey card is simply a reference.

    Original with camera auto white balance

    Using a grey card

    Corrected in Photoshop using grey card

    Color Calibration Target

    Much like a grey card provides an accurate grey, a color calibration target provides an accurate reference for colors.  I use the X-Rite ColorChecker and ColorChecker Passport.  Unfortunately, I’m not professional enough to give you a detailed explanation of exactly how it works.  All I know is that it standardizes colors in an image profile, compensating for differences in color between camera manufacturers and lighting conditions, resulting in a more accurate photograph.

    I’ve made the ColorChecker part of my workflow.  Every time I shoot, I include the ColorChecker in at least one of the photos, so that later I can use that image as a reference.  The ColorChecker software creates a DNG profile that can be used with Lightroom and Photoshop, simplifying the workflow considerably.

    Even if you are just an amateur photographer like me, I highly recommend getting a color calibration target and including it in your photos.  The ColorChecker includes grey patches, so you can use it for simple white balancing as well.

    Studio Lighting

    There are times when you require lighting consistency (for instance when publishing a book or website) or a specific lighting setup.  As most of us are not professional photographers, the simplest lighting solution in this case is continuous lighting.  Just like normal room lighting, continuous lighting is simply switched on.  The lights can then be easily positioned for the lighting you prefer.  The most affordable continuous lighting consists of fluorescent lightbulbs mounted in a fixture that is usually surrounded by a softbox.

    Below is one of my softboxes which I purchased from a cheap Chinese manufacturer.

    Fluorescent Light Softbox

    Fluorescent Light Fixture

    Color Temperature

    As a beginning photographer, I was very concerned about color temperature, purchasing only light bulbs which were 5500K.  (See Color Temperature.)  Somehow I came under the impression that a specific Kelvin temperature rating was the sign of quality.  So I was always puzzled when the colors in my photographs weren’t as rich and vibrant as the artworks themselves.

    I later came to realize that the Kelvin temperature is perhaps the least important of factors to consider when purchasing lights.  Just as with natural lighting, color temperature can be easily adjusted in software like Photoshop and Lightroom.  And using a grey card it’s very simple to achieve a neutral white balance.

    In China, restaurants are often lit with cheap, bright fluorescent tubes.  It’s possible people here are not very concerned with lighting, but I find it unappetizing and unromantic to see food and people lit like this.  It’s not just the brightness, it’s also the quality of the light.

    My cheap photography softboxes put out a similar kind of ghostly light.  Sure, they are 5500K, similar to noon daylight.  But just like in a typical Chinese restaurant, colors look lifeless.

    Color Rendering Index (CRI)

    When I finally learned about Color Rendering Index, everything made sense. From the Wikipedia article:

    A color rendering index (CRI) is a quantitative measure of the ability of a light source to reveal the colors of various objects faithfully in comparison with an ideal or natural light source.

    Where I had been looking for light sources with a specific Kelvin rating, I should have been much more concerned with their CRI rating.

    Searching through the Chinese commerce site Taobao, while almost all of the cheaper photography lighting companies tout their bulb’s color temperature, none of them even mentioned CRI. So I decided to find a bulb with a high CRI in order to compare.

    Philips Master Graphica 36W/950

    The only affordable high-CRI light source I could find in China is the Philips Master Graphica 36W/950.  This tube is frequently used in painter’s studios to provide conditions similar to true daylight.  This tube’s color temperature is 5300K (a little warmer than the typical photography light) and the CRI is 97 (very high).

    As a first test, I used a Philips double light fixture and placed it above my work desk and used it at night.  (Up until then I had only used cheap fluorescent bulbs in my studio.)  The difference was startling.  Working at night has always been a bit depressing, but the Graphica light changed the entire atmosphere of the room.  It’s a really beautiful light.

    Convinced that I was on the right track, I next tried taking some photographs with my old lights and then the Graphica as the light source.  With the exact same shooting conditions there were still subtle differences in the final photograph.  The colors under Graphica lighting just seemed richer.

    Below you can see a comparison of my regular, cheap fluorescent lights with the Graphica tubes.  (The large image can be rolled over to switch between the two images.)  Apart from the lighting, both photos were taken using the exact same conditions.  In Lightroom, I only set the ColorChecker profile and adjusted white balance.

    Regular Fluorescent Photography Lights

    Philips Graphica 36W/950 T8 Fluorescent Lights, 5300 K

    Histogram for Regular Fluorescent Lights

    Histogram for Philips Graphica

    DIY Fluorescent Photography Light Fixture

    I discovered that many photographers are already using fluorescent lights for photography.  In particular, this tutorial by Joe Edelman shows how to make your own fluorescent light tube fixtures for photography.  I made a similar version using parts that I could find on Taobao.  Because I could not find 4 or 6-tube light fixtures, I mounted two 2-tube fixtures onto a sheet metal corrugated shelving.  The corrugated sheet is light, sturdy, and convenient.

    In total I made four of these four-tube fixtures.  This is because I also help friends photograph their large ceramic paintings, and we need lighting longer than the 1.2 meters of the 36W tubes.

     

    Light fixture attached to wheeled tripod.

    Back of light fixture.

    For the photo of ceramics below, I used two four-tube fixtures as the side lighting.  In front of the fixtures I hung a sheet of translucent softbox fabric.

    Ideally, each light fixture should have six 36W tubes.  Four tubes still seems a little dark for studio photography.

    Scroll over the image to switch between my regular photography lights and the Graphica tube lights.

     

    Photographing Paintings and Porcelain Tiles

    Part of the reason for building the DIY fluorescent lights is to help my porcelain painter friends photograph their work.  In the past they used natural light on cloudy days or my cheap softboxes.  But with either of these methods it is very difficult to get consistent light over the entire length of a porcelain tile.  A one meter square softbox will not illuminate a one meter long painting evenly, as the light intensity of the softbox decreases toward the edges.

    The best way to photograph a flat reflective surface is to position two lights at either side, hitting the target at an angle of 45 degrees.  The lights are moved away from the painting until the lights’ reflections are no longer visible through the camera.

    In the session below, the lights were placed about 1.5 meters away from the subject.

    DIY fluorescent light setup for large paintings

    High-dynamic-range (HDR) Test

    You might have seen HDR images before on the internet, they were very popular for a time.  Often, HDR images appear gaudy, ghostly and surreal.  But HDR doesn’t have to look like that!

    All digital cameras have limited dynamic range.  That is, they can only record a certain range of light to dark in a photograph.  HDR is simply taking multiple exposures of the same scene and combining them in order to get greater dynamic range.

    For example, looking at the group of ceramics I photographed above you will notice that some details are lost in the shadows.  Normally I would use Photoshop to manually lighten up areas like the inside of the oilspot teabowl.  But with HDR I can capture those details using information in the overexposed shot.  This technique works even better with very light objects (like porcelain vases) on a dark background or vice versa.

    It might seem daunting for the amateur photographer, but HDR only requires an extra press or two of the shutter.  Most cameras offer a multiple exposure setting.  If you prefer to shoot manual, remember that you only need to adjust the speed, not the aperture.   (Adjusting aperture would result in varying depths of field.)  Image processing software like Photoshop and Lightroom 6 include HDR functions, all you need to do is select the files and the software does the rest.

    The large photo below is an HDR composite of the four smaller images above it.  They were combined in Lighroom 6.

    HDR can produce some interesting effects, but when photographing artwork I still haven’t come across a situation in which HDR beats a correctly exposed single shot.

    ISO 100 105mm f/11 1/3s

    ISO 100 105mm f/11 .6s

    ISO 100 105mm f/11 2.5s

    You can scroll over the image above to switch between the HDR and single-exposure photos.

  • Jingdezhen

    One ton

    One ton of porcelain stone delivered to my studio. It's only recently that I've become confident enough to make such a large investment.

  • Glazes

    Simple Microscopy for Ceramics

    The first day of Ecology class we went out to a local pond, gathered water, and returned to the lab.  I’ll never forget the amazement of viewing the water under a microscope, exploring that hidden world.

    I finally got my first microscope for viewing ceramics.  There are multiple hand-held digital microscopes available now, I went with a Chinese company, Supereyes.  The A005+ is their most expensive version and has a 5MP sensor.  It was about $150USD.

    The camera comes with Windows software.  On a Mac, you just plug in the USB cable, open Quicktime and select File->New Movie Recording.  You can either record a movie or take a screenshot.  Results are best if Quicktime is in Fullscreen mode.

    The quality of the A005+ sensor is not great.  There is a lot of noise in the image and resolution seems poor for 5MP.  Focusing works fairly well, although the focusing mechanism (rotating the top of the microscope) can be confusing.  The A005+ has built-in lights, however they produce a lot of glare on reflective surfaces.  Using ambient light or shining a flashlight at various angles works better.  It is also very interesting to view translucent ceramics with a light shining through them.

    Shining a flashlight through a late Ming porcelain export dish to view birds painted in blue & white.

    In retrospect, I probably should have gone with a regular microscope, using a handheld digital camera to record images.  (John Skaley has more information about microphotos at the bottom of his iron glazes article.)  But the A005+ is still a pretty fun toy.

    As a first test of the microscope, I thought it would be interesting to compare various clear glazes.  Personally, I prefer clear glazes that do not contain too many bubbles visible by the naked eye.

    These clear glazes were all fired in a reduction atmosphere to Orton Cone 11.  You can find the recipes to these glazes on my new recipe website, Glazy.org.

    Photomerge

    In microphotography it’s common to take multiple images of a subject at various focus depths, finally merging those images into a single image with greater depth of field.

    We can also physically move the subject around on the microscope platform without varying focal length, finally merging those images into a single, larger image.  (Just like taking a “panorama” shot on your mobile phone.)  Various software exists to merge these photos together, including Photoshop and Lightroom.

    For Photoshop the process is very simple.  Just gather your panoramic images into a single folder.  Open Photoshop and select File->Automate->Photomerge.  Select all your images and modify settings if desired.  I find that the default settings work just fine in most cases.

    Here is a recent teadust glaze I have been working on and the resulting Photoshop photomerge of the same test tile.

    Teadust glaze test tile

    Photomerged image of a teadust glaze

  • Glazes

    An old Porcelain Stone Mine

    It’s surprising to me how often archaeological discoveries seem to be made in Jingdezhen, but then I remember that wherever I walk in this place there are deep layers of shards beneath my feet.

    A friend of mine was given samples from a recently found porcelain stone mine dating from the Five Dynasties Period.  Apparently the find has not gone unnoticed- professional antique makers have been secretly mining the site.  Luckily we have the chance to acquire some of this porcelain stone.

    I’m often dealing with unfamiliar, traditional materials of which chemical analyses are lacking or unreliable.  In these cases, I usually create a series of line blends to get a basic idea of what I’m working with.  From those first tests, one can further refine glazes using more line blends and triaxials.

    For this porcelain stone I created the following initial tests:

    • Pure porcelain stone, crushed, milled and sieved.
    • Porcelain body using porcelain stone and kaolin at 15-45%.
    • Lime-fluxed celadon glazes:
      • Porcelain stone and 10-20% Er Hui (Glaze Ash)
      • Porcelain stone and 10-20% Wollastonite
      • Porcelain stone and 10-20% Whiting

    Idealized “traditional” recipes are also based on two-component mixtures.  For glazes, porcelain stone was mixed with a flux like glaze ash.  For porcelain bodies, porcelain stone was simply mixed with a proportion of kaolin.

    Usually a single line blend of either Whiting or Wollastonite could tell you a lot about a porcelain stone.  However, porcelain stone mixed with Glaze Ash or Whiting often results in fuming/carbon trapping, so I wanted to test each flux separately.  I usually also create Dolomite or Talc tests.

    I also prepared two sets of test tiles for cone 10 and 12 firings.

    Stones of all types can be used in glazes.  Joseph Grebanier’s Chinese Stoneware Glazes lists many recipes that use locally sourced granite.  And Brian Sutherland’s Glazes from Natural Sources contains a wealth of information on the subject.

    A sledge hammer is used to break off pieces of the hard porcelain stone

    A very hard mortar and pestle is used to further break down the porcelain stone.

    The crushed porcelain stone is ball milled for four hours.

    Even after milling, the mixture needs to be sieved.

    After sitting and decanting excess water, the mixture is dried on a plaster slab.

    Because I’m in a hurry, the mixture is further dried on the stove.

    Porcelain body tests with increasing proportions of kaolin.

    Fired porcelain body tests.

    Fired porcelain glaze tests with increasing proportion of flux.