Can studio light be as good as sunlight?

Question

I am currently digitalizing some family albums. I was told the best source of light is daylight, so I've been using that as a light source. However, this restricts me to specific hours of the day, makes me have to adjust shutter speed because of passing clouds, which also affects white balance, etc. It would be very nice to be completely able to control the lighting.

So I am thinking of building a mini shooting table setup as described here: http://www.subchaser.org/photographing-documents-01

The question now is, won't the quality of light inevitably be worse using artificial lighting (as opposed to sunlight)? And (assuming there is a difference indeed) is this difference a substantial one, or is it so small that one can neglect it in practice?

I'd be happy with any opinions on the matter. If you'd also feel like adding some personal experiences with studio lighting, that would be very very nice!

Answer 1

Sunlight is good but, as you note, it is also variable.

By using a good high CRI ("Color rendering index")source, as James Snell notes, and by doing tests with white balance, you will be able to get results with artificial light that have far better consistency than you can achieve with sunlight, and which are close enough to the best that sunlight can give as to be indistinguishable to most viewers.

As James says, most LED and most fluorescent lighting tends to 'have issues' due to the spectral discontinuities in the light emitted. You can obtain special high CRI fluorescent and LED emitters which have CRIs of 90 or more and which will be suited for your purpose. Even light with CRI in the 80-90 range is often usable with care in white balance adjustment and awareness of the issues involved. Some web searching on "Color rendering index" will give you a good feel to what is involved. Most white LEDs and essentially all fluorescent tubes use "phosphor" which is excited by part of the emitters light at the blue (high energy) end of the spectrum as light at other longer wavelengths. High CRI lights phosphor lights generally use a mix of different phosphors to produce a more even spectral spread.

Use of halogen or tungsten lamps will give a more yellow light than sunlight but will have an essentially continuous spectrum. Note that CRI is usually defined with respect to tungsten light so a high CRI source will have a yellow cast.

By using several light sources you may be able to achieve an excellent result with LED and/or fluorescent sources, but use of a tungsten lamp or lamps is 'easy enough' and liable to produce best results overall if attention is paid to colour balance.

As well as CRI there is the closely linked issue of color temperatures. Rather than even start on these, the references below provide an excellent introduction which will allow you to search for anything else you need from a well informed starting point.

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CRI / Color temperature / What light sources to use and why:

CRI - a good place to start - CRI - Wikipedia

Good 4 part article Color Temperature & Color Rendering Index DeMystified - possibly enough to give an excellent feel for the subject. There are arcane extras which experts will argue for aeons, but you'll be well informed by this.

REDUser discussion onLED versus fluro. Hardly definitive but useful - LED vs. Fluorescent Lighting. and TEXT VERSION - less pretty, may be easier to follow.

OSRAM so potentially "biased" BUT also useful Methods of Achieving High CRI with LEDs

Chromawhite high CRI LEDS - selling a product but extremely informative as they give a CRI value for each of the CRI test targets with a range of their products and tungsten-halogen and metal-halide bulbs - plus two 'other LED products' for good measure.

Answer 2

For some purposes, studio light can be better than sunlight, for some definition of better. Specifically, it is more flexible and easier to control.

Light has a number of fundamental characteristics, including intensity, direction, and spectrum. You can find more on these under What's the technical difference between artificial and natural light?.

The sun is very powerful, which makes it better for lighting entire landscapes than studio lighting. On the other hand, it's hard to move around; if you want light coming from a different direction, unless you are a mad scientist or have the Biblical powers from Joshua 10:13, you have to wait for the earth to spin into the proper place — while hoping the weather cooperates.

That last is another factor: sunlight is generally found outdoors, where weather is a frequent occurance. You can get the sunlight indoors using windows or skylights, but since these are generally fixed in walls and ceilings, they limit your flexibility even further. And while equipping these with glass technology will help in the event of rain, the sun will still be covered by storm clouds in that case, making it not much use.

Additionally, because the sun is very far away,^{[citation needed]}, the relative falloff of light will be smaller than that from a very close light source. That is, the effect of a small light right out of frame will be different from that of the sun even if the small light is the same relative size from the subject's point of view. (See Is there a difference between a large, far light source, and a small, close one?). Again, moving the sun closer is very difficult, and also likely to end all life on earth, so studio lighting is a big win there.

And, it's not just direction: the portable nature makes it much easier to attach and manipulate lighting modifiers. You can (and people do!) put diffusion material over windows, or use reflectors, diffusers, flags, and more in sunlight — there's an infinite realm of possibility there alone. But you're still constrained by the basic facts of nature; with artificial lighting, you work with different constraints (a bigger infinity, if you want to think of it that way).

The spectrum and light color is another issue: because the sun is a miasma of incandescent plasma, it's quite ideal for the accurate perception and rendering of all colors in an object, scene, or person. See What is Colour Rendering Index (CRI)? for a lot more on this. And also see a number of questions and answers about color temperature — What is color temperature and how does it affect my photography? is the basic one, but I also like How to recognize different lighting color temperatures?. In short, the sun is way better for color than low-cost fluorescent LED lighting, and moderately better than higher-cost versions of the same, but for most practical purposes this isn't an issue when using studio strobes, hotshoe flashes, or "hot lights" — incandescent of any sort.

In short, control is the thing, both because it increases versatility and because you can do the same thing over and over again without waiting for the time and weather to come around again.

For your specific case of digitizing family photographs, I really think it's easier to get good results with a moderate-cost scanner than with an elaborate setup with a DSLR — even a nice DSLR and a very elaborate setup. But if you do go with that, you probably want artificial light, because it'll be much easier to get consistent results.

Answer 3

The quality of light is usually measured as the CRI.

[CRI] is a standard from the International Commission on Illumination (CIE) for rating the degree to which a lighting source shows colours faithfully. A score of 100 represents an ideal "blackbody" source, like an incandescent bulb (or the sun), and scores less than that are worse. A typical awful warm-white fluorescent might score in the 60s; a better fluorescent tube would be in the 70s or 80s. A monochromatic light source like a sodium vapor streetlight might even have a negative score.

Source: What is Colour Rendering Index (CRI)?

Something you have to consider when deciding on natural/artificial light is that artificial light lets you completely control where highlights/shadows fall and also means that you have a consistent environment which can be useful for comparisons between documents. Also your exposure, white-balance etc. will always the same so once you've set it up you can forget about it which can greatly speed the processing if you have a lot of content to work through.

Realistically all you need is for your target area to be evenly lit with a decent CRI. So long as you choose your light sources carefully your needs will be capably met by the kind of setup in the question.