Flower photography.

I thought I'd pass on the following advice from a photographer who
took wonderful images of alpines in the wild. The notes were
originally intended for 35mm SLR cameras but I've found they work
extremely well with digital:

1. Try not to photograph in direct sunlight. If direct sunlight is
unavoidable try to choose early morning or late evening. If possible
provide some light shade (but not dappled shade). Strong light will
dilute the natural colour.

A diffuser or even an opaque shade can help with this. The trouble
with direct sunlight isn't so much the color balance as it is the
contrast between shadows and highlights. Diffuse illumination is
what you want. Overcast skies work for that reason.

However, you have to watch color balance. An overcast sky has a very
high color temperature and a pale yellow filter may be beneficial.
Morning and evening light tends to be warmer (i.e. lower color
temperature), and may need a filter working in the other direction.

2. Use a macro, zoom or close-up lens unless you want to capture the
plant in habitat. These lenses have a very short depth of focus and
will throw the background out of focus which has the very desirable
effect of sharpening the subject.

I'm afraid this advice has been a bit garbled. Generally speaking,
short focal length lenses have a greater depth of field than long
focal length lenses. Macro lenses for 355mm cameras typically have
focal lengths either around 50 mm or in the 90-100 mm range, the
latter having the shallower depth of field.

But any lens will have a shallower depth of field if you open the
aperture up. My very fast Pentax ƒ/1.2 50mm lens will have a much
shallower shallow depth of field at ƒ/1.2 than my Pentax ƒ/4 50mm
macro lens at ƒ/32.

I think what you've written would be better broken into two parts:

2a. Use a purpose-made macro lens, a close-up lens attachment, or
a zoom lens with a macro feature for in-habitat plant photography. A
true macro lens differs from an ordinary lens of the same focal
length in (a) being able to focus at shorter lens-subject distances
and (b) having a flat focal surface with very little barrel
distortion. True macro lenses tend to have smaller maximum apertures
than ordinary lenses of the same focal length, but this is not a hard
and fast rule.

2b. Use a wide aperture to give a shallow depth of field, thereby
throwing the background out of focus and making the subject seem
sharper in contrast. However, a known strategy for wildflower
photography is to shoot so that both the subject plant and the
background are in focus, the latter giving context to the former.

Be aware that cranking down the aperture smaller than about ƒ/8 to
get depth of field may cause some loss of sharpness from diffraction
effects.

3. The key to good flower photography is the point of focus.
Remember that anything between your chosen point of focus and the
camera will be blurred, whilst anything beyond your point of focus
will remain clear for a short distance (the depth of focus). With
close-up images it is very important to focus accurately on the
anthers if present. If not, consider focusing on the stigma. It is
usually a mistake to focus deep into the throat of a flower which
will throw the anthers, stigma and outer segments out of focus.

No comment here.

4. Learn to give yourself time to study the image through the
viewfinder before you press the trigger. Make sure your chosen
point of focus is crystal clear. Usually, what you see is what
you get.

Oh so true! One of our local folks does a lot of wildflower
photography; she pays very close attention to what she sees in the
viewfinder, and I am gradually learning to mimic her ways, removing
distracting twigs, blades of grass, etc from the scene. You've
probably travelled a long way to photograph that plant: don't be in
a rush to snap it; take your time. And take several shots while you
are at it.

My note: The above was mostly aimed at 'in the field' photography.
It is possible to get good results by using a standard lens and a
background screen but remember that the 'chosen point of focus' rule
and light consideration still applies. The depth of focus will be
much longer.

Again, I get the sense of some confusion here. My two Pentax 50mm
lenses (the very fast ƒ/1.2 and the slow ƒ/4 macro) will have
identical depths of field if set to the same aperture, say ƒ/8.

There have been some excellent guidebooks published on macro and
closeup photography. Look around for one if you want to get a better
grip on your wildflower technique.

--
Rodger Whitlock
Victoria, British Columbia, Canada
Maritime Zone 8, a cool Mediterranean climate

on beautiful Vancouver Island