Illuminating Life Sciences: A Biophysical Guide to the Use of Chromatic and White Light Sources in Photobiology

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors give a kind of introduction to various fundamentals of radiation physics with reference to existing light sources. This is not a scientific paper, but rather the content of a physics or technical bachelor's degree course.

In other, more biologically or medically oriented disciplines, however, the content presented here is probably less well known and the quantities and information on light sources such as LEDs are actually an important topic. (It is a bit surprising that the authors do not know the borders of the visual spectral range, but fortunately, these mistakes can be corrected easily).

Overall, the article is a pleasant read and is publishable after the correction process, but it seems to me to be in the wrong journal? In any case, I suspect that most readers of Photonics already know the contents of this article. So, maybe a more biological journal would be the better fit?

 

Questions/comments:

·       L. 63: You are talking about “Far-Red”. As far as I know there are (at least?) three definitions? What is the meaning here?

·       L. 177: 800 nm is no part of the visible spectrum and never in a CIE diagram.
(The line you are talking about is the “line of purples”).

·       L. 180: single wavelengths also have chromatic coordinates.

·       L. 195: Please correct all integrals in formula (5) by the correct limits of the visual spectrum (380 – 780 nm).

·       L. 196: Please replace the 800 nm in Fig. 1a by 780 nm the official upper limit of the visible spectrum in all definitions / standards worldwide.

·       L. 196: In Fig. 1b you indicate the spectral ranges of blue, green and red light. Why did you cut the blue and red region? (The lower limits of the green and the red section seem somewhat dubious to me.)

·       L. 201: please correct the 800 nm.

·       L. 215: The “monochromatic” light might be misleading. I would delete it.  

·       (L. 218: This peak shift is “Wien's displacement law”.)

·       L. 249: Why did you use the MAYA 2000, when you had the BTS254? The MAYA system might have the better resolution, but as far as I remember it is not intensity calibrated and might give totally wrong spectra (especially for broad emissions).
Please explain for which measurements you took the MAYA and how you calibrated it.

·       L. 269: Which deviation are you talking about?

·       L. 273: Why do you give such large errors for the measured peak wavelength like 9 nm for the violet LED? Both of your spectrometers are capable of much more precise measurements.

·       L. 300: You define something you call RGB model. What about the violet region below 430 nm? What about the red region above 650 nm? Why neglect these spectra ranges?
(The backgrounds in Fig. 3 differ more or less from your definitions.)

·       L. 304: Is it really fluorescence? I would suggest luminescence as long as you are unsure about the lifetime of the excited states.

·       L. 315: see comments on the colored backgrounds above. I would suggest removing them or base them on a “hard definition” (like an international standard) and extend them over the whole visible range.

·       L. 334: see comments on the colored backgrounds above.

·       (L. 361: No comment on the measured 6080 K of your 6500 K fluorescence tube?)

·       L. 422: Definition of PPFD?

·       Concerning the whole discussion: I would suggested to give a few important absorption or action spectra to discuss the sense of describing the quantitative impact of an illumination just by its color. (You can probably observe differences of an order of magnitude for the same intensity within one color.)  

Author Response

Dear Reviewer,

first, we would like to thank you for the opportunity to revise our manuscript. We agree that this is not a purely physical work, and most researchers in photonics are familiar with the majority of the described topics. However, the intended readership comprises life scientists who do not have a background in photonics. Therefore, we are confident that this paper will fit into this Special issue. In the new version, we have incorporated all your comments and suggestions, which has greatly improved the quality of our manuscript. Please find a detailed point-to-point respond to your comments.

Best regards,

Mira Mutschlechner & Harald Schöbel

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript ID photonics-3011577 has been devoted to present a study about particular light sources with potential applications for photobiology. Please see below some points to the authors:

1. My major concern is related to the absence of photobiology experiments in this report taking into account the title of the paper.
2. If possible, please comment about the influence of incident polarization in photobiology.
3. It would be interesting if the report includes a description about the potential influence of the time of exposure of the light sources studied in photobiology.
4. In my opinion, the analysis would be improved if it is considered the contribution of resonance and off-resonance interactions in the photobiology effects.
5. How is the impact of multiphotonics and nonlinear optics in photobiology?
6. It has been described the potential accuracy in the description of photoinduced effects by using fractional models in photobiology. The authors are invited to discuss some perspectives and see for instance: DOI: 10.1088/2057-1976/ad39f1
7. The main results related to the optical sources should be confronted with updated publications in the topic to see the value of the results. You can see for instance: https://doi.org/10.1080/15502724.2022.2029710
8. The advantages and disadvantages of the different light sources studied could be better visualized if they are presented in a table with better details.
9. Why the conclusion section is not separated from the discussion section?
10. In order to better justify the importance of each reference selected for the presentation of the topic, it is suggested to split the citations presented in collective form.

Author Response

Dear Reviewer,

first, we would like to thank you for the opportunity to revise our manuscript. In the new version, we have incorporated all your comments and suggestions, which has greatly improved the quality of our manuscript. Please find a detailed point-to-point respond to your comments.

Best regards,

Mira Mutschlechner & Harald Schöbel

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have succesfully clarified most of the points raised in the review stage. The analysis is solid and the topic about biophysical consideration related to chromatic and white light sources in photobiology is interesting. Then, in my opinion, this work can be considered for publication in present form. 

Comments on the Quality of English Language

A proofreading is suggested.