Re: New lens for XT ?????

jazu <nofreakingspam@xxxxxxxxxx> wrote:

Can you tell us why you don't like the pictures? What's
wrong with them?

They look to me too soft.

Stop down 1 or 2 stops.
Make sure you focus correctly.
Use a faster exposure time. (=> more light!)
Set ISO to no higher than 400 for best sharpness. Increase
ISO however before accepting too slow exposure times.
If in doubt, use a *good* tripod.
Make sure that object movement doesn't cause blur --- many sports
want 1/500s, 1/1000s or faster.
Make doubly sure the AF latches onto the _relevant_ part of
the image --- the AF may be sensitive to areas about 9
times as large as the central AF spot marker (i.e. "copy" the AF
spot marker to directly above, below, left and right of
the marker in the viewfinder, and make sure nothing there
is of stronger contrast or closer).[1]
With portraits, try to focus on the pupil of the closer eye.
If possible, decouple the AF function from the shutter
release. It really helps, but takes getting used to.
If critical focus is important and the AF is in "One Shot" mode,
trigger the AF more than once.
Remember that with a lens slower than f/2.8 Canon's AF just
guarantees that the focus point will be within the allowably
circle of confusion (as defined by Canon) of the wide-open
lens. The CoC is larger than one pixel! You may need to
resort to manual focussing and focus bracketing.
Use a lens screen. Not only does it protect the lens from quite
some abuse, it also strongly increases contrast and image
quality by keeping strong lights away from the front element.
If necessary, use your hand or some other object to keep your
front element in the shadow (unless the sun is in the frame,
then you cannot do much about it).
Do _not_ use an UV filter or protective filter of any kind for
"protection" unless your shooting conditions include sand,
salt water (spray), mud spray, or similar. Even high
quality, expensive filters can degrade image quality,
cheap filters often degrade the quality lots. (Note: if
you are using a filter for effect, i.e. gray filter,
polarizing filter, etc. that is something else.)
Make sure you expose your shots correctly. Look at the
histogram and adjust exposure if necessary.
Don't judge the sharpness exclusively on the 100% view, unless you
want to print, present or beam the image _really_ _really_
huge. Your monitor has probably 75-100 DPI, thus an 8MPix
(3504 x 2336) image at 100% would be 35x23 to 47x31 inches
(98x58 to 119x79 cm) at that magnification.
(And even at barn door size most people aren't going to get
out the loupe looking for pixels.)

Look at 1200x1800 for 300DPI 4x6 inch prints --- and
that's taking a loupe to them. I doubt most people you
show the shots to have more than 1200x1600 on their
monitors, either.



I don't like to sharp it in PC3.

Set the in-camera sharpening and contrast higher, or accept
that you _have_ to sharpen (increace acutancy) digital images.
(You do the same when developing film, but there it is a chemical
process, not a step you think about.)

Be aware that point & shoot digital cameras oversharpen and
deliver very contrasty images. They look "sharper" at first
glance, but ugly on the second glance.


Please show examples where you feel the image is not sharp.
Scale down the full image and show 100% ("pixel for pixel")
crops of areas where you think it's most noticeable. Make
sure the EXIF data is not lost, as it is important to
understand and evaluate the conditions of the shots.

-Wolfgang

[1] This is due to the facts that the screen cannot be 100%
aligned to the AF (which is in the camera bottom, btw.)
and that the active area of the AF cannot be too small.
.

Relevant Pages

  • Re: Double hires mode color artifacts
    ... expect of an Apple II, given its resolution and color limitations. ... essentially no change after the window had filled with 14 "dots". ... pixel on host pixel boundaries. ... A filter of 4 bit width in hires should be already sufficent for that. ...
    (comp.sys.apple2)
  • Re: Rookie having problems with some filter code. Any help?
    ... > Frederic Patin's paper titled "An Introduction to Digital Image ... > filter ever written". ... And then constructing a Color pixel from the filtered result? ... I don't think 'Normalizer' is of much ...
    (sci.image.processing)
  • Re: filtering specific pixels
    ... >>> but the resultant image from the canny filter is a binary ... >>> on those pixels only in my original image, ... >> What we are doing here is any pixel which is far away from your ...
    (comp.soft-sys.matlab)
  • Re: Fundamental Image Processing Question
    ... One definition of "perfect" is point sampling after low-pass filtering. ... cannot be represented accurately at this pixel density, ... you take your source image and convolve with a filter ... that has a sharp cutoff above 0.5 cycles/pixels, ...
    (sci.image.processing)
  • Re: illumination elimination
    ... The theory - Each pixel in your V plane or monochrome image ... Take your log image, and apply the fftfunction to it, apply the ... Read your filter into Matlab using imread, ... If you started life with a colour image reform your HSV structure ...
    (comp.soft-sys.matlab)