The presented work shows a very interesting study based on the analysis of measurements obtained in an eddy covariance flux observation site. It is remarkable the use of field data for the study. The use of other reference measurements is lacking, taking advantage of the fact that the study is located in an experimental area, leaf-level measurements could have been used.

Line 354. "In Figure 1c, shows a good correspondence" It will be desirable to provide a quantitative value, perhaps an error estimate, or the difference between the variables compared (with the data from the NIRv and the R-NIR in the same graph).

Understanding that the main topic is the structural effects and shadows, please explain why there were not used measurements of the fraction of vegetation shaded along daily and seasonal periods. In line 370 it is commented that the rbg camera was used to determine the sunlit leaves, but there were no further used to normalize or correlate with other variables to reinforce or discard some assumptions and unknowns exposed. For example, on line 368. "The diurnal variations... determined from the RGB". Or line 355. "The magnitude of both variables... of the given period". Did you try to normalize the values by the SZA, or by the sunlit or shaded vegetation fraction?

Lines 377-389. The SIF is correlated with the dynamics of the PAR. Obviously, PAR is one of the main factors, but the photosynthetic surface has to absorb the light. This raises the question of why PAR is used to normalize SIF to obtain SIF yield, without applying any correction factor and assuming that the entire area covered by the FOV is fully illuminated vegetation. (SIFy = SIF/PAR) and no (SIFy = SIF/APAR)

Lines 414-416. If NIRv and r-NIR give almost the same trends in the results, why do you recommend using NIRv?

Figure 1 and 3. The letters should be in the same place (e.g., top left of the graph boxes).

General comments:

They find the relative difference between Solar-induced and LED-induced fluorescence in a forest site. The interesting point from the presented RF model is the significance of blue and other visible wavelengths to the explanation of Solar/LED yield relationship(φk). Since equation 6 also consisted of APAR×fesc, the blue band, and other factors might be an alternative approach for fesc prediction, too. One of the questions is how to prove the mechanisms of blue band contribution to shadow fraction from observed data (maybe with monitoring camera data). Another point is reproducibility. A justification for diurnal FyieldLIF is lacking in explanation. The reduction in the afternoon fluorescence with LIF might be linked to those of GPP or leaf-level photosynthesis. If the relationship between FyieldLIF and the Light-Use-Efficiency of GPP is weaker than SIFy, the theoretical point will be unsolved.

Specific comments

>Table1

If the SAA is a variable of degree or radian, those can be increasing clockwise to west. In what kind of case does the sun/shade fraction increase/decrease westward? I guess those are not homogenous canopy bidirectional reflectance assumptions. If the illumination angle should be normalized to the principal plane of excitation light, the cosine of (SAA) can be a more realistic factor. Figure 4 indicates the importance of SZA and SAA in the RF model, and those definitions should be clearly and logically defined.

Abstract

>L27: geometry effects compared to FyieldLIF.

The geometry effect on LIF is addressed less in the paper. Is there any effect of shade fraction (Figure S5) before the blue LED flash on FOV? Continuously shaded leaves would react differently to other leaves under flash, and those can cause uncertainty on the Fyield.

>L29:

Could you briefly explain the implication of fluorescence seasonality? Why decreasing? Does it relate to increasing stress factor or light response to quantum yield which is related to the photochemical system openness? Also, a discussion of L486 mentioned FyieldLIF also explained by leaf biochemical and solar angles. Why solar angle is here even though the author assumes LIF output is free from geometric factors?

>L30

R-NIR can be rewritten as R850. A hyphen symbol is sometimes confusing.

>L30: the product of NIR by the normalized difference vegetation index

Grammer correction: The Product of A and B.

>L190

As far as I know, the optical system called SIF3 with HR1-T sensor is newly developed. Do you have a plan to publish a more detailed explanation of assembly, function, ability to detect signals, and so on? Also, this paper should include the figures of calibration processes, and calibrated spectra (plot of radiance and wavelengths) from upward and downward irradiance at the start and end of the season. Dark current to signal stability is not shown. There is no evaluation of Signal to Noize Ratio. Also, the retrieval uncertainty of SIF should be assessed among different approaches (e.g., iFLD, SFM, BSF, SVD……) compared with the presented 3FLD. It is recommended to enhance the reliability of the findings (especially on a diurnal variation on the O2A band, e.g., van der Tol et al 2023 RSEvol284,113304).

>L275

Please add the figure of upwelling radiance spectra at 757.86, 760.51, and 770.46 nm.

>L282

Eq (4) can be =R850 × NDVI. Misspelling?

>L300

Why φK?

There is no clear reason to choose the SIF/LIF ratio consisting of phi (φ) and k. If we look at the previous research on this topic, φ has been used for quantum yield. It seems confusing.

>L 555

Any references to blue band contributions?

>Supplementary

Figure S7 shows FyieldLIF is decreasing from morning to afternoon, and the author explained it is derived by activation of dissipation on leaf scale. How could you explain why those are independent of the canopy structural effect? As is shown in Fig S5, the diurnal sun rotation would affect the fraction of sunlit leaves when the instrument was targeting heterogeneous canopy objects. I doubt the diurnal variation of LIF is also a variable of the sunlit fraction, rather than simply explained by hemispherical integrated PAR, especially on a clear sunny day. Thus, additional analysis for the sunlit fraction of LIF would help to minimize uncertainty on target mismatch.