Frequently asked questions

Yet another LAI software? Why?
See our motivations on our home page!

Why this name Hemisfer?
The software analyses hesmispherical photographs, but the author decided to change ph to f because so the name includes the letters ISF, which is the French abbreviation for LAI (Indice de Surface Foliaire).

On which operating system can I use Hemisfer?
Hemisfer runs on Windows, either Vista, 7, 8 or 10. It should work under Windows 11, but this has not yet been extensively tested and cannot be guaranteed. It does not (yet) work with Wine under Linux.

I try to install Hemisfer but get a warning that the source of the software is not certified. Should I care?
A certificate authenticating a software is expansive and needs to be renewed regularly. Having such a certificate for Hemisfer would mean roughly doubling its price. I prefer to keep the price as it is and to continue offering a free unregistered "exercise" version.

I try to install Hemisfer on Window 10/11, but it keeps telling me that a .NET framework 3.5 is missing. How can I proceed?
Hemisfer needs such a framework to run, presently in version 3.5. This version is not the most recent one and is no longer installed by default on recent computers with Windows 10. It is planned to have the next versions of Hemisfer using the framework version 4.x. Without risking to get lost in Microsoft's instructions, it is possible to do it this way (requiring administrator rights):
- open the control panel or the computer parameters
- search for "Windows features" (which should work even if your Windows is in another language)
- check the box ".NET framework 3.5"

Is it possible to use this software for pictures taken with non-fisheye lenses (e.g. wide-angle 16mm, or even 28mm)?
Yes, the definition of the lens geometry includes this option. If the field of view is less than about 45°, however, the mean angle of the foliage becomes hard to estimate from the pictures. In this case, it may be better to restrict the foliar angle to a narrow plausible range in order to get a good estimate of the LAI.

Can I calculate the light regime prevailing at the point where the photograph was taken?
Yes. Hemisfer is able to calculate the transmission of direct and diffuse radiation through the canopy. For the incident (above-canopy) radiation, it uses a model requiring only 2 parameters: the average direct and diffuse radiation of the atmosphere.

I would need more references about how the light regime is calculated in Hemisfer. Where can I find such references?
The methods used in Hemisfer are based on the content of the following book chapter:
Schleppi P., Paquette A., 2017: Solar radiation in forests: theory for hemispherical photography. In: Fournier R., Hall R. (ed.), Hemispherical photography in forest science: theory, methods, applications. Managing Forest Ecosystems 28: 15-52. DOI 10.1007/978-94-024-1098-3_2.

I can't use the help: it tells only "Navigation to the webpage was cancelled". What can I do?
You probably installed Hemisfer and its help file on a network server. This is a known restriction of Windows' help files in general, see <http://support.microsoft.com/kb/896054>. Hemisfer tries to find out if such a restriction applies and then shows the help from the web <http://www.schleppi.ch/hemisfer/help>. This may however not work in every situation. If you get the above-mentioned error message, try installing Hemisfer on a local drive. There is no problem with the registration if you change the location of the programme's folder. Or you may prefer to rename the help file: if it cannot be found, then the online help will be shown instead.

I have an error message about lenses, that a file cannot be read. Why?
A lens name is defined in a parameter file (.INI), but the lens parameters are taken from the Lenses.csv file, which must be either in the same folder as the Hemisfer software or in the same folder as your parameter and picture files. A lens file with some of the most commonly used lenses is included in the download package.

I changed my lens file and saved it again in the same folder, but then Hemisfer no longer finds any lens parameters. What's wrong?
The CSV extension of Lenses.csv means comma-separated values. However, if you edit such a file with a spreadsheet, it may happen that it uses different separators like semi-colons. Hemisfer tries its best to cope with such differences in formats, but does not always succeed. Check the format of your lens file in a simple text editor (and compare it with the original lens file included in the download package).

After saving a file, there is an error message about an invalid function call, but actually the file is saved correctly. What's the problem?
This may be due to a shortcut (in the start menu or on the desktop) that indicates a wrong starting folder. Try modifying this shortcut (right-click, then "properties"), or replace it by a new one (drag Hemisfer.exe and drop it while holding the CTRL and SHIFT keys down).

The programme always asks me if I want to save parameters. Can I get rid of these messages?
In the options about results, you can define if your parameters are saved always, after confirmation or only by request from the user. Chose the option you prefer.

I would like to calculate only the threshold for a whole batch of pictures. What's the best way to do this?
Open all the files, remove all LAI methods from the options, and uncheck also the calculations for a single tree and the calculation of the light regime in the corresponding options tabs. Then set the 'saving parameters' option to always. Start then the analysis and the results will be saved both individually in the INI files and together in the results file.

I have problems to close Hemisfer when the results are still displayed in my text editor. What's wrong?
This problem is known for some programmes which do not handle properly the communication when they are called. If you are able to do it: modify the association of the file type (e.g. *.DAT) so as to avoid DDE calls. If this is too complicated for you (because you are just a normal human being): close the results window first and... sorry about it (but don't blame me for bugs of other software packages).

I change the γ (gamma) value but this has no effect on the LAI calculations. Why?
The γ value is used only to calculate the threshold. This means that it affects the LAI only if you let Hemisfer calculate the threshold. If your threshold is fixed or set via a parameter file, then γ has no effect.

Can I open Hemisfer several times to compare pictures?
Yes, it works, allowing you to compare also different parameters for the same picture.

I set rings of 15° width, but in the results the angles are 10°, 23.3° etc. Why these numbers?
These are weighted means of all angles within a ring.

Picture analyses from a same site don't appear in the same summary in the results. Why?
The files are treated in alphabetical order. All files from a site should thus appear together in the alphabetical list and then the summary will be based on the site name as given in the parameter files. Just give file names accordingly, for example by putting the site name or abbreviation at the beginning.

The correction of slope and non-linearity (Schleppi et al., 2007) increases the calculated LAI but it often increases also the proportion of gaps in vertical projection (Fmv). Isn't this contradictory?
At first glance yes, because more LAI, i.e. more foliage should leave less gaps open. However, the correction of slope and non-linearity often gives also a higher leaf angle, which lets the leaves appear smaller when looking up vertically.