Differing color cast from hot lights & incamera AWB shooting Raw..

<p>I shoot under available light where ever I can find it. I don't have expensive lighting setups nor do I use flash/strobes except for an occasional fill.</p>

<p>Capturing scenes in and around my home town's businesses I'm often faced with shooting under tungsten (incandescent). There's one thing I've discovered and would like confirmed from contributors here is there seems to be various color casts produced from different brands of home/business tungsten lighting that play well with my Pentax K100D's AWB.</p>

<p>Some are pleasant and some are just really bad but all give the same amber appearance according to what I see with my own eyes. See below the unedited Raw shot out of ACR of what I consider a pleasant color cast from tungsten light according to my camera's AWB.</p>

<p>I love this look but I don't always get it and I'm trying to see if it is influenced by the brand of light. This antique shop uses a variety of different brands of tungsten lighting one of which is a Sylvania reflector flood in the ceilings and another in the lamp shades which I didn't check the brand. I'm going back to find this out when I get the chance.</p>

<p>Some of the color casts range from those pictured with most giving off a red to pinkish magenta yellow bias on white walls and any other neutral object while destroying/dulling cool blues and purples. </p>

<p>Is this your experience shooting under these types of non-pro lighting and is it caused by the brand/model? </p><div></div>

<p>This is what I consider bad tungsten AWB. Just shot under clear globe vanity incandescent lighting in my apartment.</p><div></div>

<p>Learn to set manual WB with your camera. </p>

<p>http://www.youtube.com/watch?v=D_-108zwqm8</p>

<p>AWB is very difficult in low tungsten light ... especially now with energy saving bulbs that are warmer than ever before.</p>

<p>-Marc</p>

<p> </p>

<p>I know how to set WB manually within the camera, Marc. </p>

<p>I'm asking if anyone here has noticed different color casts associated with different brands of tungsten lighting using their camera's AWB.</p>

<p>I'm trying to avoid buying a bunch of tungsten bulbs just to check this out, but the idea has crossed my mind of taking my camera into a Home Depot or Lowes hardware lighting display section to see which gives the best warm rendition using the camera's AWB but there's the contamination aspect of nearby tungsten lights to consider with this route.</p>

<p>Thanks for responding.</p>

<p>I'm also wondering from examining the first image posted if the nearby window light is influencing my camera's AWB into giving such a pleasing off white warm result. </p>

<p>I guess I'm just going to have to find out for myself.</p>

<p>Old tungsten lamps will be warmer toned than new ones due to bulb blackening, 4000 hr long life bulbs are warmer than shorter life 1000 hr brighter bulbs as well. In effect, every bulb product line will have a slightly different colour temp, and it will also vary with age and applied voltage. For example, running a 120 volt bulb at 110 volts will lengthen its life substantially with a lower light output and corresponding drop in colour temp.</p>

<p> </p>

<p>That's interesting, Bob. So you think that top image's tungsten appearance is caused by these factors?</p>

<p>Have you ever gotten that kind of WB appearance from your experience with tungsten and AWB? </p>

<p>I realize I can easily adjust ACR WB sliders to get that hue of warmth with any tungsten regardless of default WB appearance but it's nice not to have to search for it and have it fall in my lap. Adaptation is tough on the eyes when getting that perfect off white warm appearance from these type of lights. </p>

<p>Setting incamera "Tungsten" preset does some really funky things to the blue channel in ACR where I have to go into the HSL panel to correct for it because the WB already looks OK but not the hue I see in the above shot. It's like searching for a needle in a haystack of a rainbow of hues and saturation levels that play tricks on my eyes.</p>

<p>Part of the problem with AWB is real low temp bulbs don't have much if any blue output. 40 watt bulbs have a colour temp down around 2600K when new, most household bulbs are around 2700. Photo floods come in 3200k and 3400k models. Halogens range from 3000 and up depending on design life. An ELC projection bulb is rated at 50 hrs and 3400K. All are tungsten bulbs.</p>

<p>So the question is, what is Tungsten on your camera? </p>

<p>I don't think there is any easy answer to fixing white balance.</p>

 

<p>Yes, there is a considerable difference between artificial light sources at any given location. There are too many variables at play: type of bulb, age of bulb, wattage, whether it's on a dimmer switch. The only way to determine that accurately would be to use a color temp meter at each location.</p>

<p>Bob, yes, there is a simple answer to fixing WB, don't shoot it incorrectly in the first place ... use manual white balance.</p>

<p>It is easier to warm up a proper WB shot in post than try to fix a badly white balanced shot afterwards, which the OP demonstrated with the toy shot with what he claims are almost unrecoverable contaminated blues ... (which isn't exactly true since it can be decently corrected with one click of the Auto Color choice in Photoshop).</p>

<p>Marc</p>

<p> </p><div></div>

<p>Page 118 in the K100D operating manual. Setting W/B</p>

<p>Again, the answers given by George and Marc are not what this topic is about and not what I'm asking. I'll reiterate...</p>

<blockquote>

<p>I love this look (tungsten AWB hue in the top image) but I don't always get it and I'm trying <strong>to see if it is influenced by the brand of light</strong>.</p>

</blockquote>

<p>Marc, btw, the hue of blue in the blue toy image you applied correction on is way off from the original which is quite cyan, but then that's not what this topic is about, is it? It's not about post processing.</p>

<p>This topic is not about whether I can fix WB in post or incamera which I'm well aware of knowing how to do, but whether <strong>brands</strong> of tungsten lights can cause the camera's AWB to give different results. This is a subject about lights which is why I placed it in the "Lighting" forum, not the "Digital Darkroom" forum.</p>

<p>Hi Tim - Ignoring specular reflections and other hot spots, many of the auto WB algorithms utilize the color of the brightest percent or so of pixels in an exposure to set the WB, assuming these are probably white or nearly so. Because of this, the exact WB can be very dependent on exactly what is in the frame. Because you are not photographing exactly the same scene, over and over, with the only variable being the mfgr of the lights, is there any chance that the differences in WB that you see are due more to exactly what's included in the scene with a smaller contribution from the variability of the lights?</p>

<p>Cheers,</p>

<p>Tom M</p>

<p>Tim, AWB is not a setting at all. It is, as Tom pointed out, the camera reacting to what is in frame at the moment. Learning to use WB is more than knowing how to change it in camera. The usual method of manual WB setting is to use a grey card or a white surface.<br>

But consider this, there is nothing that stops you using any color card to set your WB to achieve any effect you desire.<br>

To answer your question about whether or not different makes of lights influence the the AWB, the answer is yes. But then you have to take into account the actual voltage of the power supply at the time, the color of everything in the frame and all reflective surfaces around the subject, to name just a few.<br>

Trying to carry around a full range of light brands to compensate for AWB, well, can I come and watch. It would as fun as Monty Python.</p>

<p>Auto white balance plain sucks, especially with tungsten lights of various type. And some cameras sucks even more than others. Most cameras can't go low enough in AWB so as the light gets warmer (lower Kelvin) AWB gets it even more wrong.</p>

<p>Custom/manual white balance is what you want. A plain piece of white paper will do fine in most cases. A spectrally neutral white target if you want to get fancy.</p>

<p>Some lights have a discontinuous color spectrum and that means that some colors will not be reproduced correctly no matter what you do.</p>

<p>In mixed light where the light is fixed you may have to do local adjustment to the white balance. Either use a raw converter that can do local WB or just layer different versions of your image in photoshop using layer masks so you get different WB setting in different parts of the image.</p>

<p> </p>

<blockquote>

<p>...is there any chance that the differences in WB that you see are due more to exactly what's included in the scene with a smaller contribution from the variability of the lights?</p>

</blockquote>

<p>Tom, I had previously considered this but I tested it on the blue toy scene having WB metering set to spot which is tied to focus point. The center of the blue toy image is the blue toy and I got the same WB hue shifting the spot point WB metering to the white wall and got the same hue.</p>

<p>There are other shots from the antique shop under the same lights taken with different subjects that exhibit this desirable AWB hue which is why I suspect it's the brand of tungsten in this particular shop.</p>

<p>What's odd is I've gotten the same kind of AWB hue shooting in a museum lit by halogen track lighting but I have to have "Tungsten" WB preset selected. As you know the "Tungsten" preset can be a very far cry from what AWB offers. Not all tungsten light behave well with "Tungsten" preset and others AWB.</p>

<p>I'm suspecting manufacturing differences in the tungsten lights are the cause similar to what I've seen with all the brands and varieties of "Daylight/Neutral" balanced fluorescent CFL and tubes I've been experimenting with.</p><div></div>

<p>To make this more clear that it's the make of the tungsten light that's causing these differences below is another shot from the antique shop but in another room lit by a different brand of tungsten light where both AWB and "Tungsten" preset did NOT give a desired or pleasant hue.</p>

<p>And this scene has a bit of window light coming through from the opposite side of the room. </p><div></div>

<blockquote>

<p>...assuming these are probably white or nearly so.</p>

</blockquote>

<p>Tom, they had a warm glow similar to incandescent and were far from looking white. This antique shop was arranged and setup by an interior designer to give the look of home furnishings. There wasn't one neutral/white looking light in all four display rooms in this shop.</p>

<p>Tomorrow I'm going to check what kind and brand of bulbs are in the lamp in my first image I posted. I'm suspecting they're some sort of CFL, but I could be wrong.</p>

<p>Tim, It sounds like you are on the right track by trying to take the variability out of the process. As you stated, what you need to do is find a brand of light bulb that has a pleasing color to you with a guaranteed color temperature and use that when the need arises. Set your white balance to a specific temperature in camera. That way you should get repeatable results for indoor shots. If there is daylight in the mix of lighting the color temp can vary by time of day. There has been some mention of Lightroom 4 having a Color Temperature adjustment brush which sounds like a great idea. My son's shoot a lot of video and most tutorials on Video technique suggest using a specific color temperature in DSLR's and don't ever use AWB as that introduces more variables that have to be dealt with in post processing. For myself I try to never use AWB, but if you forget and shoot using the wrong white balance it can be a pain to fix. There are some bulbs at Home Depot and Lowes that have a color temperature on the label. That would be a good starting point. I guess the next question would be are they full spectrum. I think you would have to test bulbs with a color chart to assure they are full spectrum. I have shot video with my 5D Mk2 and found that the white balance changed mid clip when playing it back, when set to auto white balance. What is the camera trying to do when set to AWB? Is it trying to make everything look like it was shot in daylight? Is it like Auto Light Metering where it try's to expose whatever is metered as 50% gray?</p>

<p>Thanks for your contribution, John. I can understand how this can be an issue shooting video which can be far more challenging.</p>

<p>I'm more interested in the subject of white balancing tungsten in an attempt to go about achieving a desired "designer" hue of off white as a way to imbue ambience at the time of capture and not trying to get a technically correct R=G=B rendition or searching around for a desired hue in post long after the memory of the scene's color has faded.</p>

<p>It's always easy and quick to click for R=G=B on white or gray subject/target in the scene, but searching around for a specific harmonious hue moving sliders around in post can get time consuming especially when applying to a series of hundreds or more images for a consistent "designer" look.</p>

<p>I was under the misconception that all tungsten lights delivered the same (ugly) hue of WB (blue toy image) using the camera's "Tungsten" preset or AWB, so once I started seeing these various tungsten balanced hues demonstrated here, the idea for going about getting a consistent "designer/ambience" WB hue by finding and ultimately shooting under the right "brand" of tungsten bulb began and got me to start this topic.</p>

<p>I have no idea how camera's arrive at the WB hues they get from AWB under any given light. My Pentax K100D manual states...</p>

<blockquote>

<p><em>AWB...Automatically adjust the white balance (about 4000 to 8000K)...Daylight...(About 5200K).</em></p>

</blockquote>

<p>But I'm not as concerned about Kelvin numbers as I am about the emotional impact its hues bring to an image which tungsten has the potential to deliver.</p>

<p>One other problem you are going to find is the rapid disappearance of 40,60 and 100 watt conventional bulbs due to "energy conservation programs". All were available in 1000 hr, 4000 hr, clear, frosted and opal, plus tinted opals and transparent tints. Opal being almost an paint like finish in the bulb.</p>

<p> </p>

<p>TL: <em>"... I tested it on the blue toy scene having WB metering set to spot which is tied to focus point. The center of the blue toy image is the blue toy and I got the same WB hue shifting the spot point WB metering to the white wall and got the same hue. ..."</em></p>

<p>Hi Tim - I'm not familiar with your camera, but I strongly suspect the AWB is not tied to the focus point. If it was, when your focus point was the blue toy, the AWB should have tried to compensate for it, thereby making everything else move towards yellow compared to when you had the focus point on the more neutral wall. I could be wrong, but I'm pretty sure tht most AWB systems make their estimate based on the entire frame -- actually, the brightest, non-blown pixels in the frame -- not on a subset of those pixels selected (or weighted) by the focus point selector. They do this for exactly the reason I illustrated in the previous sentence: They could be thrown wildly off if the AWB system only looks at a small, possibly highly colored portion of the image.</p>

<p>I think that Bob S's comment that there just isn't much blue in tungsten light is on-target. There is so little that the blue channel has to get amplified by a very large amount in tungsten lit scenes, and if either (a) the algorithm which estimates how much amplification to use is slightly in error, you'll have problems, or (b), if there is a slight amount of (say) daylight mixed in with the tungsten, that can also wildly throw off the WB of the scene, as it did in your 2nd image of the dresser and chair.</p>

<p>I think the only way we are going to get to the bottom of this is by some carefully controlled experiments, ie, (a) camera on a tripod so that the area recorded doesn't change, (b)changing only the bulbs between exposures, and © excluding all other light sources.</p>

<p>Tom M</p>

<p>TM: <em>"assuming these are probably white or nearly so."</em><br /><br />TL: <em>"Tom, they had a warm glow similar to incandescent and were far from looking white."</em></p>

<p>My statement wasn't referring to the color of the light reflected back into the camera (ie, what you and the camera see), but to the true color of the brightest non-blown objects in the image, ie, what they would look like if illuminated by white light.</p>

<p>Tom M</p>

<p>Well, Tom, you got me to do my homework and reread my 208 page K100D manual and I believe you are right about AWB metering the entire frame. Unfortunately it's a bit hard to confirm due to the many cross referenced foot notes written in fine print gray boxes telling me to go to such and such page but I think I found it...</p>

<p>The spot metering setting is for manual WB which also gives the option for full frame metering.</p>

<p>HOWEVER...</p>

<blockquote>

<p>•You can use [Man.WB Measurement] in the [<strong>C </strong>Custom Setting] menu (p.107) to set the area to measure for white balance when setting manually. Even if [Entire screen] is selected, white balance of the entire screen is measured normally but the exposure metering is measured according to the [AE Metering] setting in the [A Rec. Mode] menu (p.136). White Balance is only adjusted in the spot metering area (p.137) if [spot metering area] is selected.<br>

• <em>If picture is extremely overexposed or underexposed, white balance may not be adjusted. In this case, adjust appropriate exposure and adjust the white balance.</em></p>

</blockquote>

<p>So I'm going to understand this as being AWB is metering the entire frame while custom (Manual) WB which I have set to center point metering is sampling the center which works as intended.</p>

<p>The blue toy image looks a bit underexposed, maybe that's why it looks so bad, but then I used the camera's Program mode with EV compensation set to 0.0. Here's the same shot taken with +1 EV with each possible incamera WB setting applied. </p>

<p> </p><div></div>

<p>Just a side note, I got to see the importance of using a custom <em>Dual Illuminant</em> DNG camera profile in ACR when I applied it to the "Tungsten" and Custom WB versions above where the correct cyan hue of the blue toy was brought out. Using non-dual illuminant table based camera profiles didn't change the blue at all.</p>

<p>Very interesting to see the code warriors are well in charge of our color.</p>

<p>And the mystery continues. Further investigating "Manual WB" switching between metering Full Frame and Spot setting in the C Custom menu delivers unexpected results compared to AWB's Full Frame WB metering. </p><div></div>