From: Pepe Cuellar (kueyar_at_antispamdomain.not)
Date: Thu Nov 27 2003 - 23:51:41 EST
Hi all,
if I want to take some afocal pics with my DSLR camera, wich lens is the best to do this?, do I need a macro lens or a zoom lens or a normal fixed lens?, wich focal distance is the best? Thanks in advance!
Pepe Cuéllar.
AstroWeb de Pepe Cuéllar:
http://astroweb.tripod.com.mx
Lat: 20º 40' N
Long: 103º 20'W
----- Original Message -----
From: "EarlyBird"
Date: Fri, 28 Nov 2003 04:43:21 -0000
To: digital_astro_.at._yahoogroups.com
Subject: [digital_astro] Re: Joanne's digital zoom theory seems to be correct.
But done this way, doesn't the non-digizoomed pic require
interpolation/resmapling? Ie, if we use full digital zoom and record
at 640x480, my theory has been that no resampling occurs. But if we
use no digital zoom and record at 640x480, we are resampling - in
Jose's case, from 2288x1712 to 640x480. Shouldn't that in and of
itself result in a performance decrease compared to, in effect, both
shooting and recording at 640x480? Or does "downsizing" in this way
not really degrade performance? Still seeking enlightenment on this
one. I think some moon shots may be the best real world test of this
- a nice bright, high contrast target.
- JoAnne
--- In digital_astro_.at._yahoogroups.com, "jasuro" <jasuro_.at._a...> wrote:
> I'll try that tomorow in daylight and report back. However,
> translating that into practical terms would mean using a higher
> magnification eyepiece at the telescope as the means of achieving
> the larger image. with optical zoom. I'm already using 280x at the
> eyepiece with my regular setup. Bringing it to 560x would do the
> trick. I did try this with Mars last summer by using a 2x barlow and
> the result was kind of mixed. The file size increased dramatically
> because there was much less black background for the JPEG algorithm
> to "ignore". This made for much longer record times and a much
> smaller stack set, and that in turn increased the noise.
>
> Take Care,
>
> Jose Suro
> Tierra Verde, Florida
> http://web.tampabay.rr.com/jsuro/
>
>
> --- In digital_astro_.at._yahoogroups.com, "maven1981" <maven8_.at._n...>
> wrote:
> > Interesting Jose,
> >
> > But to be even more conclusive, try this...
> > shoot one 640x480 picture with full digital zoom.
> > set the camera to full optical zoom and physically move the camera
> > closer to the bar code until it's fills up as much of the screen
> as it
> > does in the digital zoom picture. Shoot one at 640x480.
> > Then you'll have a digital zoom and optical zoom image where the
> > target looks the same size. That will really tell you if the
> sharpness
> > is real.
> >
> > Tony.
Yahoo! Groups Sponsor
ADVERTISEMENT
Before posting an image to our group please read the space mangement guidelines:
http://groups.yahoo.com/group/digital_astro/files/Photos%20Section%20Space%20Management%20Guidelines
Please check the digital_astro FAQ at:
http://www.szykman.com/Astro/AstroDigiCamFAQ.html
Be sure to visit the digital_astro Gallery and Archive at:
http://velatron.com/dca/gallery
http://velatron.com/dca/archive
Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
-- ___________________________________________________________ Sign-up for Ads Free at Mail.com http://promo.mail.com/adsfreejump.htm ------------------------ Yahoo! Groups Sponsor ---------------------~--> Buy Ink Cartridges or Refill Kits for your HP, Epson, Canon or Lexmark Printer at MyInks.com. Free s/h on orders $50 or more to the US & Canada. http://www.c1tracking.com/l.asp?cid=5511 http://us.click.yahoo.com/mOAaAA/3exGAA/qnsNAA/N_XolB/TM ---------------------------------------------------------------------~-> Before posting an image to our group please read the space mangement guidelines: http://groups.yahoo.com/group/digital_astro/files/Photos%20Section%20Space%20Management%20Guidelines Please check the digital_astro FAQ at: http://www.szykman.com/Astro/AstroDigiCamFAQ.html Be sure to visit the digital_astro Gallery and Archive at: http://velatron.com/dca/gallery http://velatron.com/dca/archive Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
This archive was generated by hypermail 2.1.7 : Thu Nov 27 2003 - 23:51:52 EST