Optimising the focus is needed to get sharp images and good counts. The best basis for sharp images is to use a small aperture I. E. using high numbers for aperture in the camera configuration. Inly if time is getting linger than 0.5 s to reach optimum brightness aperture should be opened.

LT Counter standard
The Camera of the LT counter standard has the possibility to use the auto focus once when creating a new measurement series (Click on “set focus recommended”). This may be done to maximise sharpness if enough sharp objects are to be seen. If colonies are very small or do not have sharp rims manual setting of the focus is preferred. Using of permanent auto focus must be avoided as mechanics may be destroyed if the focus is not able to find a sharp object e.g. because no plate is in the counter. Additionally refocusing needs time and may make image acquisition more slowly.

Click on “set focus recommended” for use manual set of focus in each camera configuration to acquire sharp images.

LT Counter digital
The camera of the digital counter does not allow to fix a certain focus once defined. As aconsequence each image is focused individually. Using the fast advanced focusing technology this is no problem as long as the a maximum aperture possible is used (see above) and there are at least some larger sharp objects in the image. This is generally true as long as at least the rim of the petridish is visible on the image. This is of high importance esp. if the agar is very homogenous and colonies are extremely small or have no sharp rims and may appear at very low numbers.

Please ensure that one or more medium sized objects with sharp rims are on each image to be used by the auto focus.