Tungsten and Fluorescent Lighting 2

The exercise here was to look at 2 different types of fluorescent lighting and compare the colours. As I has already looked at fluorescent lighting in the earlier part of the exercise I thought it was useful to compare the fluorescent lighting we have (CFL), with the other lighting we have which consists of the small halogen bulbs. These give a very intense point light, and again come a ceiling fittings or as single reading lamps. The light appears a very bright white to the eye.

A halogen lamp, also known as a tungsten halogen lamp, is an incandescent lamp with a tungsten filament contained within an inert gas and a small amount of a halogen such as iodine or bromine. The combination of the halogen gas and the tungsten filament produces a chemical reaction known as a halogen cycle  which increases the lifetime of the filament and prevents darkening of the bulb by redepositing tungsten from the inside of the bulb back onto the filament. Because of this, a halogen lamp can be operated at a higher temperature than a standard gas-filled lamp of similar power and operating life. The higher operating temperature results in light of a higher color temperature. This, in turn, gives it a higher luminous efficacy (10–30 lm/W). Because of their smaller size, halogen lamps can advantageously be used with optical systems that are more efficient in how they cast emitted light. (Wikipaedia)

Trial 1.

These were taken in my study, which has a single CFL light as the ceiling fitting. It is not very bright and takes a long time to 'warm up' to full brightness. The light appears yellowish to the eye.

I chose a still life of blue and greenish objects set on a blue cloth. The colours were possibly too similar, but I wanted to see how the camera would cope with differentiating them.

AWB

The AWB setting actually coped surprisingly well. The cat is possibly a bit too creamy, and the owl a little green but the other colours are accurate.

Incandescent

Oddly enough, the white balance setting for 'incandescent' , which I assume was developed for using with tungsten bulbs, worked reasonably well in the setting, although the owl is too green. It had not been at all effective in the previous setting in the living room with a different type of CFL bulbs. (see previous post).

2500K setting

My camera does not give any specific settings for fluorescent lighting, but it does give the option to set the white balance to a specific colour temperature. The packaging for the bulb gave the colour temperature as 2500K so I set the white balance to reflect this. This is the most successful so far, The cat is now a little too white (possibly slightly overexposed), but all else is correct.

Set WB

Here I used the setting where I had set the white point. This is the best of all, with accurate colours. (the cat is still possibly slightly overexposed).

Trial 2.

For this trial I moved to the kitchen where the ceiling fitting has the small halogen bulbs that are very common now. I used the same still life.

AWB

AWB has given a very poor rendition of the colours. The blue cloth looks pale purple, and the owl is an odd grey-green.

Incandescent

The incandescent setting, which should , in  theory, work, is rather better, The owl is slightly too blue, but the colours are generally acceptable.

2500K

 For comparison I also tried the 2500K setting that had worked well in the study with the CFL bulbs. Here everything definitely has a much too blue cast.

Set WB

The set white balance has been less successful here, again everything looks too blue, and the brown edge of the unit that just shows has lost all warmth.

These exercises clearly show  how important it is to consider white balance when taking photographs with artificial light.  The CFL bulbs do seem to be slightly more 'forgiving' although to the eye the look both dim and slightly orange. The halogen bulbs (although looking neutral to the eye) can give some very odd effects! It is clear that I need to think about white balance is taking pictures in the kitchen.

Or there is an alternative option:

Lightroom

Take the best option (the one using the incandescent white balance setting) and alter it in Lightroom (or PSE). The advantage of shooting in RAW. This has ended up with the best colours of all.











Learning Points:

• don't always rely on AWB
• think about the type of light, and compensate accordingly
• not all CFL's give the same effect
• you may need to alter further in post-processing to get the correct colours

Tungsten and Fluorescent Lighting

This exercise is now increasingly difficult to do because of the changing law and the lack of simple tungsten lights available. All the lights in our house are now the long lasting compact fluorescent light variety or halogen lights.  I performed a similar exercise looking at the lights (CFL) in the hall and out the door. When my eyes had adjusted to the outside light and I looked back inside the light was definitely orange. Conversely, when looking back outside, the evening light appeared bluish.

On measuring the light inside the living room, which appears reasonably bright to the eye, at ISO 100, and f/4.5, the shutter speed varied between 4 seconds in the brightest part of the room and 3 minutes in the dullest part, clearly not holdable by hand, and unlikely to give a sharp photo of a person. I am certainly aware that reading by the artificial light without an extra ‘reading lamp’ is getting increasingly difficult.

Interior and Exterior.

As previously noted we do not have any tungsten bulbs, so this exercise was carried out in the living room which is lit by a ceiling fitting of 5 small CFL bulbs.

Trial 1.

On investigation my camera does not have and automatic - fluorescent setting for white balance - so I did some experimentation.

AWB

This image was taken using the camera's AWB setting. Both the colour and exposure are reasonable. The internal light was from a overhead fitting of CFL bulbs that are diffused though  opaque glass light shades.

Incandescent

Here the white balance was set to incandescent, this is clearly not at all the right setting for these CFL bulbs and gives an overall blueish tinge both to the area of the pot lit by the internal lights and the outside area. Not a success.

Trial 2.

I then decided to experiment a little and see if I could get a better result in camera, without relying on post-processing. By now it was later and there was less light outside.

AWB

Again the camera's AWB setting has done a reasonable job. The curtains and the orchids have a fairly accurate colour and there is no overt colour tint to the outside, the window frame is a little bit warm in colour (it should be grey).

Daylight

This was taken using the camera's daylight setting. It gives a warmer glow to the picture, more pleasant although rather less accurate  colours.

Incandescent

As previously, the incandescent setting does not work for the light generated by these bulbs.

Set whit balance

For this image I choose a white balance that I had previously set to a white card. This gave a very similar effect to the 'daylight' setting, possibly slightly more accurate, but still slightly warm.

This was an interesting experiment. Previously I would almost certainly relied on the AWB setting of the camera. I would not have used the incandescent setting, but also probably not used the daylight one. When taking pictures in our living room, which will usually be of family, the rather warmer 'daylight' setting is likely to give a more pleasing effect than the 'cooler' AWB setting.

Exercise - Judging colour temperature 2

Looking at the images in the previous exercise is interesting. I fine the uncorrected images taken in the shade are too blue and would alter them for ant use. The evening ones, while very orange actually simply remind me of evening sunlight and I am happy with them.

While waiting for an opportunity ti encourage a child to pose for me to finish this exercise I took a range of images using AWB, daylight and shade settings to compare them.

In the shade.

These pictures of the windmill at Cley-next-to the Sea were taken in the late afternoon on a cloudy day. All settings except the white balance were the same, except for the first image which was taken at a faster speed and which I had to lighten down.

AWB - ISO 100, f/13/ 28mm efl, 1/320 sec

This image is taken with AWB.Here the colour is reasonable - although it does look like the windmill was taken in sunlight (which it wasn't).

Daylight - ISO 100, f/13/ 28mm efl, 1/125 sec

With the white balance set to daylight the picture is a more natural colour, however still looks too 'sunny' compared with the reality.

Cloudy - ISO 100, f/13/ 28mm efl, 1/125 sec

Here the white balance was set to cloudy. The effect is much more like the real day, with clouds that have only a minimal amount of blue.

This shows an interesting effect of using the AWB setting. The camera software has 'assumed' that I was shooting on a sunny day an compensated accordingly, while the day was actually very dull. Altering the setting to cloudy has been much more effective in accurately portraying the feeling of the day.

Sun.

This picture of a giant thistle was taken on a sunny afternoon. 5 minutes later it clouded over and began to rain! All images had the same settings other than the white balance.

AWB - ISO 100, f/3.3, 1/125 sec.

This image was taken using AWB - and is a reasonable reflection of the actual colours, although the Abbott House in the background is actually an even brighter pink.

Daylight - ISO 100, f/3.3, 1/125 sec.

With the white balance set to daylight the Abbott House is a more accurate colour, but the thistle is a bit too orange (warm).

Shade- ISO 100, f/3.3, 1/125 sec.

With the white balance set to shade the whole image is much too orange and looks like it was taken in the evening.







In these pictures taken in fairly bright sun in the mid-afternoon both AWB and the daylight settings have given a reasonably accurate portrayal of the thistle. AWB was better for the thistle itself and daylight for the building in the background. The 'shade' setting gives a pleasing, but totally inaccurate rendition.