I attached the picture of the slit. It's from the "standard" desktop spectrophotometer kit that was purchased from here. Any tips with regard to getting it sharper would be greatly appreciated! Also, is there any way to download the spectra (with actual data points) where it could be manipulated (ie, subtract spectra from one another, manipulate, etc using something like Excel)? Thanks so much warren!

Yes, you can download in the left-hand column on the spectrum page, it's a small grey bar with XML,JSON, CSV download links.

So you think your brightness issues are solved?

For sharpness, you might try refocusing the webcam. I'm not sure which version you have -- was there a wood block in the kit? If so, perhaps moving the camera further from the slit would help.

Hi dckim. One may get sharper and bright images by reducing the slit width (by cutting a narrower slit in a new black card) but then you loose brightness rapidly if the light source is not right in front of the spectrometer slit. Theoretically the diffraction signal -proportional to the entering intensity times sine(width)/width to the square- will reach a peak in sharpness reducing the slit width but the light entering the slit reduces and the overall spectrum intensity drops, the area of the slit is reduced so the amount of light passing through it.

Hi, Dckim - I just got your email. Can you upload a screenshot of the "Configure" panel in the Capture interface? I think you may need to adjust where you are taking your sample row. Also, if you can dim the light a lot, I think that will also help.

Hello Warren! I have attached a screenshot of the "Configure" panel in the Capture interface using four different light intensities (at the very top of this thread). They are labeled "pic10", "pic11", "pic12", "pic13" with the last file being at the lowest light intensity I can produce on my dimmer.

I also attached pictures (at the very top) of my "countertop" spectrophotometer in case there is something wrong in the way I built the thing. Any comments or help please????

Hi - it doesn't seem like it's lined up with the light bulb; but you could try to diffuse the light by placing a piece of semi-transparent (milky) plastic in front of the imaging slit? Or a thin piece of paper (tracing paper...), although paper usually has UV dyes in it so it'll fluoresce a bit.

Finally, I got some interesting data.....BUT the results confuse me. I am looking at algae in a petri dish placed between the light source and the spectrophotometer. I then compare the results with water in a petri dish placed between the light source and spectrophotometer. I expected the intensity of the algae at certain wavelength (like 400-450 and 650-700 as those are the wavelengths for chorophyll) to be reduced versus that of just plain water since I thought that's how adsorbtion spectroscopy works. Increase in chorophyll and algae should correspond to lower intensity at those wavelengths associated with chorophyll, right? However, I am seeing higher intensity in the spectra for the algae vs that of water. What am I missing? Any advice or help would be appreciated.

Can you post links to some of your spectra demonstrating this? I think it might be best to just post a research note with some photos of your setup and links to your data, so we don't get too off-topic on this particular thread.