FOV confusion (DKF41 vs DFK21 & ToUcam)
While I read the IMS camera spec of DFK 41AU02.AS (color, 1280x960, USB version), I found it states that the CCD chip (Sony ICX205AK) is 1/2" type which I thought theoretically doubling the FOV of DFK21 and ToUcam that use the 1/4" type (ICX098BQ)Later, I learnt the 1/2” ICX205 actually has pixel size 4.65 x 4.65 microns. This is obviously smaller than the 1/4” ICX098 with pixel size 5.6 x 5.6 microns. It also means the FOV of DFK41 is only 4.65 x 2 / 5.6 = 1.66 or 66% wider than the FOV of DFK21 or ToUcam, not DOUBLE as I expected initially.
I also found the DFK41 runs up to 15 f/s only, no better than ToUcam at equal frame rate.
Now I wonder if I should spend HK$5,000+ for DFK41 to upgrade from the HK$600 ToUcam !!
A bit confusing to me. It taught me a lesson that the advertisement of 1280x960 1/2" type CCD does not guarantee a FOV two times greater than the 640x480 1/4" type. You really have to see what "size per pixel" when buying larger FOV cameras.
AC
[ 本帖最後由 mca 於 2009-8-18 14:58 編輯 ] BTW,does anyone knows the "video" mode of Canon 500D is compatible with Registax stacking software ?
AC I have used DMK21, 31 and 41. For lunar and solar photography, I find that DMK31 strikes a good balance with reasonbaly big CCD size, good fps (30fps), and not-too-long computation time when stacking. With DMK41, I usually find that only part of the field is sharp due to seeing problem. It is hard to pick a really frame for stacking. The computation time is also very long due to larger number of pixels.
Unless low magnification full moon mosaic is your interest, I would not recommend DMK41.
Having upgraded from Toucam to DMK 2 years ago, I never look back. The difference is just too large. All high magnification photos in my moon website here were taken mostly with DMK31:
http://www.imsc.edu.hk/pages/moon/
[ 本帖最後由 astroQM 於 2009-8-18 18:50 編輯 ] I got DMK31 already.Stupid I was, I bought it in 2007 Aug at HK$6,000. Within 2 years, it cut price crazily to ..... :Q . The worst of all, it only gives 30% more FOV than ToUcam in lunar photography, out of my expectation of 60% more.
FOV is top consideration in my lunar work, frame rate and noise etc are only secondary concern.
Anyway, I thank your advicee not to invest on DMK41, I forget it now.
Alan Chu 原帖由 mca 於 2009-8-18 15:19 發表 http://forum.hkas.org.hk/images/common/back.gif
BTW,does anyone knows the "video" mode of Canon 500D is compatible with Registax stacking software ?
AC
Yes, please refer to discussion on how to convert 500D Full HD video to 1920 x 1080 avi format and stack using RegiStax 5 in Occultation Forum
http://occultation.freebbs.hk/thread-5809-1-1.html Dear W C
Thanks for the link. I shall try to digest it, quite a no. of video format jargons.
AC The video from DSLR is quite highly compressed, but worth a try if you have one already.
A very preliminary example taken a few nights ago:
http://osastrolog.blogspot.com/2009/10/20091004-jupiter-with-canon-100-400mm.html While I read the IMS camera spec of DFK 41AU02.AS (color, 1280x960, USB version), I found it states that the CCD chip (Sony ICX205AK) is 1/2" type which I thought theoretically doubling the FOV of DFK ...
mca 發表於 2009-8-18 14:41 http://forum.hkas.org.hk/images/common/back.gif
Hi,
The mono series 21 is a 1/4-inch CCD (4.5 mm diagonal, 4.60 x 3.95 mm) and each pixel is 5.6 x 5.6 micron.
The 31 series is 1/3-inch CCD (6 mm diagonal, 5.80 x 4.92 mm) with pixel size of 4.65 x 4.65 micron.
The 41 series is 1/2-inch CCD (8 mm diagonal, 7.60 x 6.20 mm) with 4.65 x 4.65 micron pixels.
FOV calculations should be based on the chip size, not pixel size.
Please refer to attached data sheet.
PTS
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