Please read the following table in HTML format from a webpage and then answer the question in detail according to the table. Each table cell is defined by a <td> and a </td> tag. Each table row starts with a <tr> and ends with a </tr> tag. 'rowspan=m' and 'colspan=n' represents a cell spaning over 'm' rows and 'n' columns.

Webpage title:
Hubble Ultra-Deep Field
Table title:
Observations
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=1 rowspan=1 > Camera </th><th colspan=1 rowspan=1 > Filter </th><th colspan=1 rowspan=1 > Wavelength </th><th colspan=1 rowspan=1 > Total exposure time </th><th colspan=1 rowspan=1 > Exposures </th></tr>
<tr> <td colspan=1 rowspan=1 > ACS </td><td class="highlighted"  colspan=1 rowspan=1 > F435W </td><td class="highlighted"  colspan=1 rowspan=1 > 435 nm </td><td colspan=1 rowspan=1 > 134,880 s (56 orbits) </td><td colspan=1 rowspan=1 > 112 </td></tr>
<tr> <td colspan=1 rowspan=1 > ACS </td><td class="highlighted"  colspan=1 rowspan=1 > F606W </td><td class="highlighted"  colspan=1 rowspan=1 > 606 nm </td><td colspan=1 rowspan=1 > 135,320 s (56 orbits) </td><td colspan=1 rowspan=1 > 112 </td></tr>
<tr> <td colspan=1 rowspan=1 > ACS </td><td class="highlighted"  colspan=1 rowspan=1 > F775W </td><td class="highlighted"  colspan=1 rowspan=1 > 775 nm </td><td colspan=1 rowspan=1 > 347,110 s (144 orbits) </td><td colspan=1 rowspan=1 > 288 </td></tr>
<tr> <td colspan=1 rowspan=1 > ACS </td><td class="highlighted"  colspan=1 rowspan=1 > F850LP </td><td class="highlighted"  colspan=1 rowspan=1 > 850 nm </td><td colspan=1 rowspan=1 > 346,620 s (144 orbits) </td><td colspan=1 rowspan=1 > 288 </td></tr>
</table>
Question:
How many filters were used on the camera on the Hubble Ultra-Deep Field, and what were the wavelengths that the filters focused on?
Answer:
Four filters were used on the ACS, centered on 435, 606, 775 and 850 nm.