Thank you both for your help and information
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Venger - Having realised how inaccurate my "eye-view" estimating can be from mistakes in an earlier posting, I now base my estimates on the relative size of the subject to the sensor frame. I generally try and get as large an image as possible to maximise detail so (apart from large subjects) am usually within 90% of max subject size on sensor.
In this instance I used my little Canon A50 which covers an area of 40x30mm with my standard zoom setting at closest focus. I don't go as far as actually overlaying the image in Photoshop (as you see below) but in my mind I see something like:
Thanks for the species list No9.
I'll take your advice and go with
Tegenaria sp. and add a link to this thread.
Bruce