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Photography in Museums


The ideal settings for your digital camera are:



ISO 80.

1/30 second or faster shutter speed with image stabilisation, 1/125 second or faster otherwise.

F8 aperture to give the best combination of depth of field and sharpness.





In practice, it is difficult, usually impossible, to satisfy all of the above requirements when taking photographs in museums. A compromise is needed for sharp photos.

The ideal of F8 for aperture is always the first to be abandoned. The small improvement in the image obtained by using F8 for the aperture is completely swamped by the effects of the other restrictions, except in perfect conditions.

The easiest way to get reasonable sharpness is to manipulate the ISO which your camera uses.

If you have a camera equivalent in Artificial Intelligence (Automatic Mode) to my latest camera, a compact Sony RX100 II, the following is probably of academic interest only.

It is usually, though not always, better than my estimate of what will give the best and sharpest image, even after manipulation in PhotoShop. In contrast to earlier cameras, it uses the slowest shutter speed that can be compensated for by its excellent camera shake technology, which means that it uses the lowest ISO (ASA).

The only time I can get a better image is by resting my lens assembly against the glass of the display cabinet, which allows me to use ISO 80, which sometimes allows me to get a sharper image than, say, the ISO 400 which the camera has determined.

But for hand held images, the automatic mode has no equal. I suspect that it takes multiple photographs as well as the normal 'image stabilisation' magic tricks to achieve this result. Often there are multiple clicks, followed by a message 'processing image' on low level light photographs.

ISO

ISO determines the speed of the 'film' in your camera. Lower speed (80) gives higher definition than faster speed (800 or more).

All other things being equal, you will get much finer detail if you keep the ISO to the minimum, typically 80 ISO. However I read that some cameras do not have this as 'native' but have it as an option, presumably by simulation, which means that it is not what it claims to be. I shall have to experiment.

This is a laudable aim, but it is sometimes either difficult or impossible to achieve in practice, in the milieu of Museums. You will sometimes be forced to use an ISO of 400 or more, which reduces the sharpness of the image, in order to get shutter speeds of 1/30 second or less.

Typically museums do not allow you to use flash, with the notable exception of the British Museum in London.

Thus your lighting will be that provided in the glass case. The problem is that many of the materials on display in museums are degraded by light, in particular painting media and textiles, so the museum directors often install lighting which is at the bare minimum needed to actually see the exhibit, and in some cases somewhat below that limit.

If you use the programmable section of your camera dial, rather than the automatic option, you can tell it to do some things that will help you in this aim:

1. Set the ISO to 80 or 125
2. Set the 'EV' or Exposure Variable to -1/3, -2/3, or -1.
3. Where you are able to use flash, set the EV for flash to a similar level, or to 'fill-in' flash mode.
4. Modify the above if you look at the preview (or the resulting image, after downloading to your desktop PC) and find that there is not sufficient exposure.


1. Set the ISO to 80 or 125

If the preview tells you that the time the shutter will be open will be longer than 1/30 of a second (e.g. 1/5 second), you will need to set the ISO to a higher value, or use automatic in order to bring it to 1/30 or 1/60 of a second or faster.

I will assume that your camera has a 'camera shake reduction' or 'image stabilisation' capacity. Without that, you will have great difficulty getting good results in museums. However, all technology has its limits, and as far as I can tell, 1/30 of a second is, at the moment, the slowest you can go with a modern camera and still get excellent results. Slower speeds usually give poorer results in my experience, even if the camera lens assembly is completely stable, as when resting on the glass of a display cabinet.

Readers who have had experience with older, non - image stabilisation cameras will know that the normal speed for a hand-held camera was typically 1/125 second. Below that, you had to use a tripod. Tripods are usually not allowed in museums, because of the danger to other patrons of the splayed legs causing obstruction and accidents. Some have resorted in the past to 'monopods' or what looks like a camera on a walking stick. These are better than nothing.

2. Set the 'EV' or Exposure Variable to -1/3, -2/3, or -1.

Setting the EV to -1/3 rather than the zero setting will typically give you better results for all your photos, including well lit sunny landscapes and so on, since it tends to avoid the lack of detail in highlights, and give a better tonal range for many digital cameras.

Inevitably, however, with 'larger' negative values such as -1 (or up to -2 which is about the limit), the photograph will look 'darker', and will need later manipulation using Photoshop or a similar programs to bring it up to what most people would regard as optimal brightness and contrast. This can be achieved by modifying the 'levels' on the photo, moving the right hand slider up to the first place that the graph shows a small positive value.

3. Where you are able to use flash, try setting the EV for flash to -1/3, -2/3, or -1, or to 'fill-in' flash mode.

You will need to experiment to determine the characteristics of the images from your camera when flash is used with these EV values. In general, an EV of -1/3 will be an improvement on zero.

From the specifications for the RX 100 II section of https://www.dpreview.com/ ,

Fill flash used for this portrait created a nice overall exposure of our model, albeit on the slightly bright side. As with the RX100, flash output can be slightly unpredictable and occasionally too bright. The camera provides flash output compensation of +/- 2 EV.


Flash is a last resort. With a flash on the camera, it will reduce the relief of the object, and will often introduce unwanted highlights from the glass display case, and from reflective parts of the object. It may also 'wash out' the image, making it far too bright, which is why you should experiment with negative EV values for flash.

However, the use of flash will usually force your camera in automatic mode to use a low ISO value, and a speed of 1/60 second. This is one of the few times when you can set the aperture to F8 and get away with it. The speed of 1/60 which may be displayed on the camera preview is usually academic, since the flash is very much faster than this, typically 1/1000 second, and especially if there is little ambient light, there will be no 'ghosting' from light other than that from the flash.

I have occasionally had to set the flash to a large positive value such as +2 in order to get enough light on an exhibit at the back of a very deep cabinet. The objects at the front of the case were totally 'washed out', of course, but I got good illumination of the ones hanging on the back wall.

However, this seldom happens in most museums. The cabinets are usually shallow, and in any case flash is rarely allowed.

Good natural lighting is the best, but 'needs must when the devil drives'.



The effects of a high ISO level


In black and white and colour emulsion film cameras, film typically came in a range from 64 ISO (formerly designated 64 ASA, as in Kodak slide film from 1962 onwards) to 100 ISO for ordinary purposes in black and white film.

'Faster' film was reserved for special purposes, and was often anywhere from 200 to 400 ISO, such as Kodak Tri-X. To achieve this, the grains of the emulsion were (typically) made larger, which meant that although shots could be taken in smoky dark nightclubs and jazz venues, the resulting photograph was inevitably 'grainy', and usually high contrast as well. 'Pushing' the film with longer development times could boost this ISO rating considerably, to 800 or even 3200 and above, at the cost of grainier photos. Many photographers made a virtue of this necessity.

When digital cameras came out, the opportunity existed to have extremely high ISO ratings, of 1 000 ISO to 16 000 ISO and above. Unfortunately, a price has to be paid for this as well, at least at the present.

'Noise' in the context of colour images, is the occurrence of randomly coloured spots on the image which bear no relation to the reality which was meant to be recorded. They are usually more obvious in darker parts of the image. The equivalent for audio is the scratchiness heard on an old vinyl recording from the 1920s, or the buzzing of a poorly adjusted or cheap microphone/amplifier setup.

The problem is that light is not infinitely divisible. It can be thought of as minute individual particles called photons, which impinge on a computer chip, which then converts them to red, blue and green values for each pixel, the pixels or dots making up the image. If each receptor on the chip is thought of as a bucket, there will be a finite number of photons for each bucket. More photons, less 'noise', less photons, more 'noise'. Noise is bad. In modern digital cameras, it shows up as a washing out of detail, of which more later.

Larger chips allow for more pixels (good) and more photons per pixel (good), but they are difficult to fit into the camera so that the lens focuses correctly on all portions of the chip, and, more importantly, a large chip is difficult to use with an 'optical zoom', that is the ability to zoom in on an object without loss of clarity.

Digital zoom simply increases the size of the original image, without increasing clarity or useful pixels. The original pixels are simply repeated, and an algorithm is applied which smooths out the resulting pixellation. In my opinion this is not worth having if you have image software which can achieve the same or a better result later, such as Photoshop.

A small chip can have a very large optical zoom (good) fitted to the camera, up to 100x at the moment, but it will suffer in terms of either fewer pixels (fewer is bad) or graininess (lots of grain is bad) or both. Typically both.

When digital cameras first came out, this graininess was apparent under low light conditions, when the ISO is automatically bumped up by the programming in the camera.

(insert examples)

This was the case in 2007/8 when I had a Canon.

insert examples)

However by 2014 this graininess largely disappeared, and was replaced by what I call a 'smearing' effect:

insert examples)

When the ISO was 100 ISO or below, there was still marginal graininess, easily fixed by using a Photoshop filter, but there is no way to recreate detail which is not there, which is what happens when the camera pushes the ISO above 200 ISO.

It is most noticeable in 'flat' or 'featureless' parts of the image. Parts of the image with a lot of texture are, to some extent, immune from the worst excesses of this feature.

(insert photos here)

What seems to be happening is that the computer chip in your camera is trying to get rid of the pixellation, or noise, and where there is good texture, this succeeds to some extent, but it does not succeed at all when the area lacks definition, when, for example, it is a flat, featureless surface such as a smooth part of a sculpture or wall.

I suspect that, although this will always be a problem, improvements in the detector chips that accept light from the lens will cut down on the noise, and thus the loss of definition.

With the cameras that I have, it is definitely noticeable on any ISO above 200 ISO, and very noticeable at an ISO of 800 or above, to the point where the photos (of museum artefacts) can sometimes be unusable.



Check what the automatic setting does on your camera

My latest camera, a Sony Cyber-shot RX100 II does an excellent job in museums. I now find that it is rare that I can do a better job by adjusting ISO and EV values than the camera does on the automatic setting. In low light conditions, which is the case in most museums, the camera sets the shutter speed to about 1/30 second, and the ISO value to the lowest value consistent with that speed.

However I cannot have both automatic and my own EV values at the same time, so for specific shots, with some experimentation, I can do slightly better than the automatic setting. It is usually not worth the time involved.

It should be realised that older cameras often do not have the sophisticated software that the Sony does. You will have to experiment with your camera.

Torres Strait
The almost limitless ability to increase sensitivity of the chip to low light levels can deliver some amazing effects. Here is a photo taken by moonlight of the small settlement of Thursday Island from a cruise boat passing through Torres Strait, using the channel known as the Prince of Wales passage.

Note that no flash was used, the brightness of the ship's side on the right comes from a little soft light from the ship's cabin.

Not zoomed in, focal length 24, 1/4 second, 12800 ISO.


Torres Strait
Note that this (zoomed in) photo demonstrates that the ability to cope with low light conditions is not infinite. The photo is darker, and much more noise is evident.

The reason for this is that when you zoom in, you are asking a lot more of your camera. Effectively there is less light available, so the camera bumps up the ISO, and increases the time of exposure. Both of these are likely (or certain) to degrade the resulting image.

Even when the camera is rock steady, as when it is resting on the glass of a museum display, a shutter speed longer than 1/30 second increases noise, for reasons I am unsure of - but it is empirically demonstrable on the cameras I use.

Zoomed in to focal length 62, 1/5 second, 25600 ISO.


Torres Strait
The navigational hazard of Hammond Rock with Hammond Island behind.

The ability of modern cameras to take hand held photographs like this with nothing but moonlight for illumination is nothing short of astounding to someone who used to use black and white 125 ASA (now 125 ISO) film for preference.

I developed and printed my own photographs in a home darkroom for many years, choosing the exposure of the image in the enlarger and the contrast of the print, which gave good control over the final image. I did my own 'Photoshopping' by dodging or burning in on individual exposures, added extraneous material (such as a cut out of a long exposure of Halley's comet to a later photo of my family looking earnestly into a blank night sky) to create special effects.

This technology was overtaken and made obsolete by digital cameras and manipulation by image processing software such as Photoshop.

Focal length 24, (not zoomed in), ISO 10000, 1/4 second.






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