In this text first a presentation of the biophotons phenomena will be done and latter it will be associated (with experimental proofs) to two phenomena and the use of their effects in religious (in concrete christian religion) context: painting of saints and other people with auras around the head and the image generated in the shroud of Turin.
Biophotons are electromagnetic emissions that all type of cells and organisms generate and can be detected outside them, the wavelength of those emission are from 200 to 800 nm, comprising ultraviolet, visible and near-infrared bands of the electromagnetic spectrum.
There are numerous scientific paper and laboratory studies working with this topic for example and as introduction here a quote:
-  Ultraweak Photon Emission in Cells Coupling to molecular pathways, applied magnetic fields, and potential non-locality
"Several papers and experiments have shown spontaneous photon emission from virtually all living systems tested [Popp, 1979a; van Wijk, 2005]. The amount of photon emission has been quantified by Popp to be anywhere from 10 6 - 10 7 photons · s-1 · m-2 of tissue. In the literature this spontaneous photon emission has been termed many things including biophotons, bioluminescence, and ultraweak photon emission (UPE). Generally, these are all referring to the property of small amounts of light emitted from a biological system. These biological systems emit photons as a component of multiple chemical processes from (very likely) many sources and mechanisms.
Typically, UPE is a product of the chemical reactions of oxygen, specifically reactive oxygen species. However it should be noted that reactions of oxygen are not the only source of UPE from cells. With any metabolic reaction there will be the subsequent release of a photon. The ensuing photon release can be a marker for activity. However, more recently it has been discussed as a possible “purposeful product” of cell functioning [Sun et al, 2010; Choi et al, 2012]. The production, role, and theoretical possibilities associated with UPE have significant implications for biomolecular mechanisms."
I think that is important to note that one thing that is not totally elucidated is the origin of this photonic phenomena, lots of papers assume that the origin is on the chemical reactions of reactive oxygen and nitrogen species of the cell, but as it can see in some other studies this could not be totally true and other origins may be at play, As an example some quotes:
-  Optical spectral analysis of ultra-weak photon emission from tissue culture and yeast cells
" Results indicate that the photon emission from both cell cultures is detectable in the six from eight examined wavelength ranges with different percentage distribution of cell suspensions, particularly 450-475, 475-500, 500-525, 525-550, 550-575 and 575-600 nm. The wavelength range of spectra from 450 to 550 nm coincides with the range of photon emission from triplet excited carbonyls (350-550 nm). The both cells cultures emitted photons in wavelength range from 550 to 600 nm but this range does not correspond with any known emitter."
-  Spatiotemporal Imaging of Glutamate-Induced Biophotonic Activities and Transmission in Neural Circuits
" Previous studies on other types of cells have shown that the origin of biophotonic activities is mostly a result of the generation of various reactive oxygen species (ROS), the common products of aerobic metabolism (mitochondrial respiration) [37,38]. Here, we found that the increase of biophotonic activities by the application of glutamate was not correlated to the change in aerobic metabolism because cytochrome c oxidase inhibitor did not completely block the initiation and maintenance of biophotonic activities. Therefore, our findings suggest that the glutamate-induced biophotonic activities may comprise the component of active biophotons that play a role in biophotonic transmission in neural cells and neural circuits, while aerobic metabolism may only be involved in the generation of background biophoton component, as proposed in our previous study ."
-  Enhancement of biophoton emission of prostate cancer cells by Ag nanoparticle
" It was also confirmed that singlet oxygen contributes to biophoton emission, that Ag nanoparticles increase this contribution, and that there are secondary mechanisms independent of singlet oxygen by which Ag nanoparticles contribute to increased cellular bioluminescence, possibly through plasmon resonance enhancement of intrinsic fluorescence."
There is a theory that say that the origin of biophotons is in DNA while undergoing conformational changes. This phenomenon would be the source of squeezed and coherent photons and is a form of communication. The experimental observation shows that different DNA conformations correspond to different intensity of biophoton emission [G. Qiao, Biophotonics, Sciences Press, Beijing, China, 2007]
For example Fritz Albert Popp, one of the pioneers (in the second technological era for the studies of this phenomena, starting in the late XIX century) maintain that DNA is a source and using special techniques, that include single photon counters, established that: (i) the radiation originates from an almost perfectly coherent photon field; (ii) essential sources of the radiation are DNA and corresponding resonators in the cell; (iii) the mechanism involves photon storage in cavities and informational channels turned by Casimir forces; (iv) there is close connection to delayed luminescence which corresponds to excited states of the coherent photon field; (v) the occupation of the photons in the phase space is the same for all wavelengths and extends up to the so called hot radiation of the body; (vii) the radiation is the proper regulator and information carrier of life.
And other autors maintain that sources may be different for distinct wavelength of the emission; one for the Ultraviolet (UV) Biophotons and other for the Infrared (IR) Biophotons
-  Meaningful UV and IR photon-exchange within bio-tissue? — Interdisciplinary evidence, and a new way to view asbestos toxicity
" Cope (1973) argued that standard mitochondria had the right dimensions to serve as resonance-chambers for the IR produced by ATP metabolism."
" Many mitochondria are much thinner than “standard” size, lying along microtubules, and with cristae spaced in a way consistent with UV-related experiments. UV-production entails onerous extra energy-accumulation, possibly via ROS-likeb metabolism."
" So, (e.g.) in cases where IR and UV appear to be emitted equally, one might argue that (at source) the IR would be much more abundant than the UV. That would be consistent with expectations that ATP-based metabolisms will usually deal in relatively low energy IR quanta; and that (in contrast) UV emissions would thus require special-and-rare procedures. Such rarity is postulated in general terms by vanWijk,[25 pp.192-193 ] concluding that: “The probability of such an event would be extremely low but definite, fitting well to the extremely low luminescence yield…” — and he says so in the context of a need for E-fields of the order of 1 to 100volt/µm, which could be destructive if misapplied (see below). On the other hand, it is possible that UV sources might also be more prolific, but that (compared to Cope’s IR) their photons may be more purposively chanelled via microtubules so that fewer escape at the initial-wastage stage."
Also it may be taken in account ordered water inside biological structures as a source and storage for those emissions:
-  Ultraweak Electromagnetic Wavelength Radiation as Biophotonic Signals to Regulate Life Processes
" As reported by Wernet et al.  in the year 2004, triangular chains, 3-dimensional rings and even triangulary pyramids are found in the molecular arrangement of water. The nuclear physicist Emilio del Giudice from Milan (Italy) found coherent regions in water . Light is composed normally from photons of different wavelengths compared to the colours of a rainbow. As del Giudice emphasizes, coherent photons are very likely to a single, intense colour. According to his research, water is able to pick up information of other molecules similar to a DVD writer and player. This is even possible if the originated molecule is disappeared. This important observation is further corroborated by the Japanese physicist Kunio Yasue and his colleagues . They found that water molecules are capable to transform disordered energy in coherent photons, a process called supra-radiation according to the physicist Dicke ."
-  Variable Viscosity of Water as the Controlling Factor in Energetic Quantities That Control Living Systems: Physicochemical and Astronomical Interactions
" The variable values of viscosities of water containing ions, that can range by a factor of 10 between bulk and interfacial (adjacency to surfaces) forms, could contain the intrinsic energy that are functional boundaries for physiological changes important for cell survival. Temporally patterned and specific strengths of weak magnetic fields can interact with the viscosity-related energies to affect the spectral power density of photon emissions and absorptions that can simulate the essential geometric and temporal parameters of the living system including intracellular organelles such as vesicles and the width of the plasma cell membrane."
Anyways independent of the origin (in any case modulated by the organism state and capable to have information purposes) very important is the fact that they are detected in neurons, and possibly they have an important function in the mind integration or consciousness generation (with the implication of microtubules, an important structure of the cells. especially in neurons, with among others skeletal-like function inside cells, that surely serves as waveguide for UV photons)
As it can be read in the paper also cited previously and others:
-  Spatiotemporal Imaging of Glutamate-Induced Biophotonic Activities and Transmission in Neural Circuits
" To address our proposal, we observed the glutamate-induced biophotonic activities in mouse sagittal brain slices and found that the extensive biophotonic activities were located at the area of the corpus callosum and the thalamus, and were significantly decreased by the application of PP2A inhibitor (OA), suggesting that the extensive biophotonic activities in these two areas may mainly originate from axons or axonal terminals in the corpus callosum and thalamus, respectively, which may be at least partly due to the active biophotonic transmission along the axons or axonal terminals of cortical projection neurons (Figure 4J).
Interestingly, the initiation of biophotonic activities by glutamate is independent of the action potential and extracellular and intracellular Ca 2+ , but the maintenance of the maximal effect was influenced when the action potential was absent or when the extracellular and intracellular Ca 2+ were removed constantly. However, both the initiation and maintenance of biophotonic activities were significantly affected by the application of a regional anesthetic (procaine), suggesting a new possible mechanism for anesthetics by interfering with biophotonic transmission via the inhibition of action potential and the function of microtubules . These results illustrate biophotonic activities and transmission in relation to electrical and chemical transmission, and it seems that either electrical or chemical transmission may only provide a basis for the initiation and mintenance of biophotonic activities and transmission."
-  Collective Behavior of Water Molecules in Microtubules http://www.researchgate.net/profile/Andrei_Nistreanu/publication/282151394...
" In this model, Microtubules are considered as quantum cavities. Their role is to provide a single mode of biophoton field, in such a way that water molecules to be considered not as independent individuals, but rather as whole, in this manner water molecules are embedded in and interacting with a common radiation field. In the model proposed, collective behavior of water molecules is characterized by coherent water states analogous to Bloch states, whose main feature is to trap biophotons in a collective fashion. Finally some applications to electroencephalography are considered."
-  Superradiant coherent photons and hypercomputation in brain microtubules considered as metamaterials
" Several studies have suggested the theoretical possibility of considering human brain as supercomputer using superluminal evanescent photons eventually generated inside its microtubules to manipulate quantum bits in brain. In a previous work we have shown that in the water trapped inside brain microtubules could exist the conditions to allow a spontaneous QED quantum vacuum phase transition towards a macroscopic coherent quantum state characterized by a phased oscillation, at a rescaled frequency, between the water molecules states and an auto-generated electromagnetic field associated to a suitable electronic transition in them. As a result a self-trapped field of superradiant superluminal photons is just generated inside microtubules, characterized by an evanescent tail whose penetration depth is greater than the thickness of microtubules cylinder. In this way the interior of the brain MT cylinders can be considered as a resonant cavity for such superradiant photons whose refraction index depends on the rescaled coherent oscillation frequency. On the other hand it is already theoretical known and experimentally proven that a near perfect tunneling and amplification of evanescent electromagnetic waves is possible in a waveguide filled by a metamaterial. In this paper, basing on the consideration of some structural analogies between man-made metamaterials and some natural biological structures, we just propose the idea to interpret the inner medium of the brain microtubules cylinder as having the properties similar to those characterizing metamaterials and so able to specifically enhance the propagation of evanescent photons inside the neurons."
-  Genomic instantiation of consciousness in neurons through a biophoton field theory
" Specifically the process of radiative relaxation of the electro-solitons allows for the transfer of energy via interactions with deoxyribonucleic acid (DNA) molecules to induce conformational changes in DNA molecules producing an ultra weak non-thermal spontaneous emission of coherent biophotons through a quantum effect. The instantiation of coherent biophotons confined in spaces of DNA molecules guides the biophoton field to be instantaneously conducted along the axonal and neuronal arbors and in-between neurons and throughout the cerebral cortex (cortico-thalamic system) and subcortical areas (e.g., midbrain and hindbrain). Thus providing an informational character of the electric coherence of the brain -- referred to as quantum coherence. The biophoton field is realized as conscious field upon the re-absorption of biophotons by exciplex states of DNA molecules."
-  Ultraweak photon emission in the brain
-  Entanglement Between Bio-Photons and Tubulins in Brain: Implications for Memory Storage and Information Processing
-  Biophoton signal transmission and processing in the brain
-  Magnetic Field Configurations Corresponding to Electric Field Patterns That Evoke Long-Term Potentiation Shift Power Spectra of Light Emissions from Microtubules from Non-Neural Cells
-  Congruence of Energies for Cerebral Photon Emissions, Quantitative EEG Activities and ~5 nT Changes in the Proximal Geomagnetic Field Support Spin-based Hypothesis of Consciousness
Here taken in mind what is described above we can take the following paper with a more open aptitude (anyways is a scientific paper with correct technical specifications of the experiments and how they take photographs), and see the photographs of the auras in the Ultraviolet spectrum as a real fact.
-  Anthropological analysis of human body emissions using new photographic technologie
In the study, they photograph auras (composed by ultraviolet photon emissions) around the head of meditating people. And they propose that because the UV band is in the margin of the human vision capacity some "gifted" people had the opportunity to see or perceive some kind of light around the head of some "special" people (or normal people in "special" aptitude) that finally has reflected in the tradition of painting (especially in religious paintings) with auras around the "saints", of course it does not mean that those people in concrete have had an aura or a special aura. Only that the tradition have collected this phenomena.
Althougt the author take in consideration de Hameroff-Penrose theory of quantum computation in microtubules I am not a partidary of this theory because I saw it as excesively recherche and specifical (to microtubules) and I am partidary of a more extensive and general theory of conscioussnes based on electromagnetic fields. You can see my website http://emmind.science to see papers related to this (including those that I am citing in this text), but is not of vital importance to the question treated here: that those auras painted in the head of people in religious paints is inspired by a real phenomenon (ultraviolet biophotons) that some managed to view (or "sub-view") and extended it to paint tradition.
Another somehow related you have available this paper about biophotonic auras in plants (and how the probably are used in intercommunication)
-  Imaging “Auras” Around and Between Plants: A New Application of Biophoton Imagin
In this regard it must be say that plant cells also have large populations of microtubules, and that plant microtubules share properties with those of animal neuronal microtubules.
The relationship of this religious relic with biophotons is that a group of scientifics has created an image with similar characteristic of that of the shroud of Turin using Ultraviolet laser pulses and because there are Biophotons in the Ultraviolet band, they have coherent properties (like laser) and are pulsed emissions.
The paper describing the experiment is here and I will copy-paste the main results that they achieve:
-  Superficial and Shroud-like coloration of linen by short laser pulses in the vacuum ultraviolet
" I. We obtained a linen coloration only in a narrow range of laser parameters. In particular, the temporal duration of the single laser pulse must be shorter than 50 ns [31,32]. While a short laser pulse width is necessary for obtaining a coloration, the VUV laser spectrum allows a coloration limited to the outer surface of the threads.
II. The most interesting results were obtained with VUV light. The permanent linen coloration is a threshold effect, i.e., the color is obtained only when F T > 22 J=cm 2 ; see Table 1. When the F T value is above threshold, the linen is ablated and/or vaporized, while when F T < 13 J=cm 2 the linen does not change color. Even when F T is in the coloration range, not all the irradiated fibers are colored (Figs. 5 and 16) due to the spatial fluctuations of energy density of the laser pulses shown in Fig. 15.
III. We triggered a photochemical coloration process. In fact, the thermal heating associated with UV and VUV radiation is within a few degrees centigrade and therefore irrelevant for the purpose of coloring by scorching linens; see Fig. 13. This result fits with the “cold” coloration process of the Shroud estimated in [8,11,12].
IV. The hue of color depends on the wavelength and on the number N of laser pulses, which is proportional to F T . Irradiations at 0.308 μm generate a brownish coloration, while the 0.193 μm photons produce a yellow color (see Fig. 4) comparable to the color of the Shroud image. In both cases, the contrast slowly increases with the number of laser pulses, allowing an accurate control of the RGB value by varying F T.
V. The different hue of color obtained by UV and VUV radiation isdue to different chains of photochemical reactions respectively triggered. In particular, the VUV radiation at 0.193 μm is absorbed by alkene groups in degraded cellulose, whose number increases with F T , thus inducing a photolysis of the cellulose, which promotes the formation of chromophores; see Fig. 14. These chromophores determine the yellow coloration of the fibers [8,12,39–41].
VI. We observed an irradiated fiber whose coloration was possibly confined in the primary cell wall [35,36], which is comparable with the thinnest coloration depth observed in the fibers image of the Shroud of Turin [8,11,19].
VII. Aging can be a concause of linen coloration. In fact, after laser irradiations that, at first, do not generate a visible coloration of linen, a latent coloration appears either by artificial (Fig. 8) or natural aging of linen [32,35]. Latent coloration is interesting for the synergy between UV, oxidation, and the dehydrating effect of heat (or of aging), which triggers the coloration process, and also for historians, attracted by the possibility that, whatever may have caused the Shroud image, the coloration may have developed over time.
VIII. The partial inhibition of fluorescence induced by VUV laser radiation (Fig. 9) is an additional feature of our coloration similar to the Shroud image. The induced fluorescence is also capable to selectively recognize the uniformity of F T incident on linen; see Figs. 9(a) and 9(b).
IX. Both UV and VUV radiations coloring linen are compatible with the absence of image under the bloodstains on the Shroud because in this spectral region light is absorbed by very thin layers of blood hemoglobin. According to  the UV light may be responsible for another special feature of the Shroud: the red color of blood stains after so much time since their deposition.
X. Using a petrographic microscope, we have observed some defects induced by UV radiation in the structure of irradiated linen fibers (see Fig. 12), similar to very old linen fabrics [11,46].
XI. Absolute reflectance measurements show that, when irradiated in the UV and VUV, our linen behaves like the linen of the Shroud; see Fig. 10."
Of course, the intensities may be distinct of those normally originated in the biological systems, but this can be relative because on one hand in some meditation techniques the biophoton emission could be hundred of thousand times greater than the normal emissions:
-  Electromagnetic Emission from Humans during Focused intent
" The count rises to approximately 8 or 10 photons per second with human control subjects in the darkroom. In a recent series of tests with groups of three subjects in the darkroom doing healing meditations, the photon count typically rose to approximately 40 to 60 photons per second. When the subjects were instructed to stop meditating, the count consistently dropped back to the baseline of approximately 8 to 10 photons per second. Three individual subjects on multiple occasions have emitted 400,000 to 800,000 photons per second over a time span of several seconds."
And on the other hand also can be take in consideration that during the death process of an organism there is a variation of photons emitted, during a little time photon number is at high level, it is larger than that in the normal state. (but in the case of these experiments with poor rats not much more)
-  UPE Biological Death Process Identification System
(also I am not sure if the causes that argued in the paper are true, I believe that during death microtubules that guide UV biophotons broken, and those photon escape outside.., maybe is fantastic but has some logic for me)
Is interesting to see in the context of the Shroud of Turin investigation how the only radiocarbon dating made until today is controversial, a priory when three independent samples of the shroud were sent to three independent laboratories they concluded that the shroud was medieval (dated sometime between 1260 - 1390), but due to some incongruences between samples analytics and those from shroud the christian church invalidated it, but is interesting that those who select and cut those minimal parts where from inside Vatican and not scientific people, and there are also suspect declarations, etc... all the history is well described here:
- The Biggest Carbon 14 Dating Mistake Ever
and some other contextual info in http://rationalwiki.org/wiki/Shroud_of_Turin
My personal opinion is that Shroud of Turing is a another fraud relic and that even Jesuchrist never existed.. To evolve to that opinion I read the book of Richard Carrier
- On the Historicity of Jesus Why We Might Have Reason for Doubt
You can search some interesting debates in youtube and take your own opinion.
I have a website where I am collecting papers that point to an electromagnetic nature of consciousness (http://emmind.net), I have a panpsychist view of life and also I think that we are only parts of bigger things, like cells in our body, My philosophy crash with christian philosophy. I hate the christian prepotence and dogmatism along history too.