lens quality

wrote:

In message ,
paul wrote:


Eric Gill wrote:

There *is* an issue that makes over f/16 impractical on most digital
bodies, where a Hassy can easily do f/45. This can make a big difference
shooting certain subjects, such as rooms, when the entire field needs to
have good focus.


Why is that? I've used f/22, 36, 45 on my D70 with various lenses.
You've got to get the dust off the sensor though.


As the aperture starts to get really small, the entire image starts to
get blurrier and blurrier. There comes a point where you lose more to
diffraction than you gain by theoretical DOF.

IOW, the smaller the aperture (or higher the f-stop), the greater the
depth that is in near-maximum focus, but the less sharp that the maximum
can be.


Oh, and my overambitious 28-200 zoom goes to f/36 but the 70-200 only
goes to f/22. The 28-200 looks awful at f/36 usually. I will admit
that... but sometimes it is useful.

In message ,
paul wrote:

OK but that's true for film too. I suppose this is more of an issue with
digital because of the crop factor then, especially compared to MF. Are
tiny P&S digicams not able to get small apertures? I don't understand
why when I add a 2x teleconverter to my 200mm, it goes from f/22 to
f/45. I haven't worked with it much but it seems fine at f/45. Maybe
because it's such a big klunky lens to start with.

There is no change in *aperture* when you put a TC between the lens and
the camera. The change is in "f-stop". The f-stop is the ratio of
focal length to aperture. The aperture in both cases is 9.09mm.
--


John P Sheehy

In message ,
paul wrote:

OK but that's true for film too. I suppose this is more of an issue with
digital because of the crop factor then, especially compared to MF. Are
tiny P&S digicams not able to get small apertures? I don't understand
why when I add a 2x teleconverter to my 200mm, it goes from f/22 to
f/45. I haven't worked with it much but it seems fine at f/45. Maybe
because it's such a big klunky lens to start with.

There is no change in *aperture* when you put a TC between the lens and
the camera. The change is in "f-stop". The f-stop is the ratio of
focal length to aperture. The aperture in both cases is 9.09mm.
--


John P Sheehy

In message ,
paul wrote:

Oh, and my overambitious 28-200 zoom goes to f/36 but the 70-200 only
goes to f/22. The 28-200 looks awful at f/36 usually. I will admit
that... but sometimes it is useful.

Sometimes you want a tremendous range of depths that are all just
slightly away from being sharp!
--


John P Sheehy

In message ,
paul wrote:

Oh, and my overambitious 28-200 zoom goes to f/36 but the 70-200 only
goes to f/22. The 28-200 looks awful at f/36 usually. I will admit
that... but sometimes it is useful.

Sometimes you want a tremendous range of depths that are all just
slightly away from being sharp!
--


John P Sheehy

rafe bustin wrote in
:

You'd have to explain why an area of
silicon 3.75mm square can capture about
the same degree of detail as a square
of film 6.35m square -- and with far
less noise. (Ratio of areas ~3:1)

As a dramatic example:

These two images are of the same subject, in the same office but not the
same angle, but with a film rig and my 20D. On the left is the Hasselblad
contender, shot by one of the better know and extremely successful (i.e.,
damn well equipped) photographers in Houston, and scanned with a high-end
Hell drum scanner. On the right is mine.

http://www.nightskyimages.net/Hasselblad-vs-20D.jpg

(On a side note, his was shot almost eight years ago, mine this morning,
which is why Houston developer Randall Davis looks a bit different).

Both are 100% crops.

rafe bustin wrote in
:

You'd have to explain why an area of
silicon 3.75mm square can capture about
the same degree of detail as a square
of film 6.35m square -- and with far
less noise. (Ratio of areas ~3:1)

As a dramatic example:

These two images are of the same subject, in the same office but not the
same angle, but with a film rig and my 20D. On the left is the Hasselblad
contender, shot by one of the better know and extremely successful (i.e.,
damn well equipped) photographers in Houston, and scanned with a high-end
Hell drum scanner. On the right is mine.

http://www.nightskyimages.net/Hasselblad-vs-20D.jpg

(On a side note, his was shot almost eight years ago, mine this morning,
which is why Houston developer Randall Davis looks a bit different).

Both are 100% crops.

I'm talking about the sie of film grains and sensors. There is no
comparison.

See:
http://www.imx.nl/photosite/technica...ilmbasics.html

Search for the term "1 micron scale" to see the picture of film grain
comapred to the 1 micron scale.

David J. Littleboy wrote:
wrote in message
oups.com...


"There's no question that modern CMOS/CCD sensors capture far more
information per unit area than film.

You're out of your ****ing mind. Film grains are hundreds of times
smaller than sensors.

No, he's quite right. Consider a 16x24mm area of ISO 400 film and
what an
8x10 print from that would look like: seriously disgusting. Now look
at an
8x10 print from a 6 or 8MP Canon or Nikon dSLR at ISO 400: maybe not
as good
as MF at 8x10, but nowhere near as problematic as half-frame 35mm.

Now consider a 6.6 x 8.8 area of ISO 100 film printed at 8x10 and
look at an
8x10 from the Sony F717. An even larger difference, although the
Sony's
pretty poor compared to the dSLR.

David J. Littleboy

Tokyo, Japan

Oh, and my overambitious 28-200 zoom goes to f/36 but the 70-200 only
goes to f/22. The 28-200 looks awful at f/36 usually. I will admit
that... but sometimes it is useful.

Sometimes you want a tremendous range of depths that are all just
slightly away from being sharp!

And if you can't turn off auto-focus, the best you can do is stop down
the lens all the way.... Good tip. :-)

-Joel

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Free 35mm lens/digicam reviews: http://www.exc.com/photography
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Oh, and my overambitious 28-200 zoom goes to f/36 but the 70-200 only
goes to f/22. The 28-200 looks awful at f/36 usually. I will admit
that... but sometimes it is useful.

Sometimes you want a tremendous range of depths that are all just
slightly away from being sharp!

And if you can't turn off auto-focus, the best you can do is stop down
the lens all the way.... Good tip. :-)

-Joel

----------------------------------------------------------------------------
Free 35mm lens/digicam reviews: http://www.exc.com/photography
----------------------------------------------------------------------------