Hello,

Perhaps in the age of digital images it would be better to express all
data at a pixel level. Just mention the pixel dimension and the number
of pixels in each axis. I think this is the most objective way to deal
with because a lot of image manipulations can always alter scaling. On the
other hand we stay with clean images that eventually can be used for other
things.

We also have to take into account that z resolution is dependent of
refractive index of the object. This is notalways controlled properly.

Patrick

 Further more On Thu, 29 Jul 1999, Dr. Andrea J.
Elberger wrote:

> Confocalists - The following message was sent in reply to my comment
> about preserving a scale bar within a projected z series:
>
> Could I just chip in and say that in one way, it would be
>      misleading to retain a 2D scale on a 3d data set projected into 2D.
>
>      This is because on a projection, making an xy measurement between
>      features which are also separated in z would simply be a mistake!
>
>      Anna Smallcombe PhD
>      Senior Applications Specialist
>      Bio-Rad Microscopy Division
>
> I agree that this is not going to lead to exact measurements, but I have
> the following comments:
>
> 1) Back in the bad old days before we had CLSMs, we took photographs of
> tissue sections that contained a z component that was limited by the
> depth of focus of the optics. We then made measurements of distances,
> lengths, sizes, etc. which in effect made xy measurements of features
> that were often separate in z. This may now be exaggerated using CLSMs
> because of the ability to get a greater z extent into the 2D projection.
> To do this on a more exact basis would require a huge number of
> calculations because it would require measuring withing many members of
> the z series of images. Although theoretically possible, it sounds very
> impractical to me.
>
> 2) I find that reviewers always ask for a scale bar, even of a projected
> CLSM image. Therefore, it is necessary to provide this kind of
> measurement in any image.
>
> Anyone have any thoughts, particularly about #1?
>
> ANDREA ELBEGER
>
> ---
> Dr. Andrea J. Elberger
> Professor, Anatomy and Neurobiology
> Director, Confocal Laser Scanning Microscope Facility
> The University of Tennessee, Memphis
> 855 Monroe Avenue
> Memphis, TN  38163  U.S.A.
> tel: 901-448-4101
> FAX: 901-448-7193
> <mailto:[log in to unmask]>
>

Patrick Van Oostveldt
Lab. Biochemistry & Molecular Cytology
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