The price of the SD1M is still way too high!

Started Apr 12, 2013 | Discussions thread
Lin Evans
Lin Evans Forum Pro • Posts: 17,355
Re: The price of the SD1M is still way too high!

DaSigmaGuy wrote:

Lin Evans wrote:

DaSigmaGuy wrote:

Lin Evans wrote:

Roland Karlsson wrote:

DMillier wrote:

I wonder whether an interchangeable mount is possible - a kind of modular mounting system that can be swapped out for a different mount without the use of fussy mechanical ebay adaptors?

Yes, its possible.

But ... I have a hard time seing what good that would do Sigma.

I think Pentax shall do a mirrorless camera that is compatible with K-mount via such a modular mount.

In a way, they have already done that. My Pentax Q can use K mount lenses via the Pentax K to Q adapter. In fact, that's why I bought the Q so I could connect it to a DA 55-300 and shoot at nearly 1700 mm at F/5.8..


Lin, you do know that your not actually getting 1700mm focal length and that all your actually getting is the field of view equivalent of a 1700mm lens?  Crop factor does not increase magnification, you simply get a narrower FOV for a given focal length lens.

Come on Alf - I've been at this a few years- I don't need a lesson in physics - LOL...

Let's put it this way, when I put my CP990 on my Meade ETX-90 and shoot at an "equivalent" 5989 mm I can get images not possible with "any" of my dSLR's regardless of the lens or lenses I use. To the telephoto shooter, it matters not the technicality of "how" it's done; the important thing is that it "can" be done. By the way, there is a little bit more to it than the field of view. There is the fact that the entire complement of the sensor's available photosites are vested within that tiny field of view. Try cropping a capture from a Nikon CP800E on an 800mm f/5.6 with a 2x teleconverter to the field of view of 5980mm and show me the "quality" of image you get and tell me how many pixels paint the area of the subject. Why don't you write and tell Canon to stop advertising their SX50 HS as having a 1200mm zoom. Hey, it's only a field of view thing.... Here's an example at 5980mm:


Nikon CP990 - Meade ETX -90 at 5989 mm (35mm Equivalency)

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Not sure how you worked that out Lin...The CP990 is 115mm equivalent on the long end and the Meade is 1250mm FL.  115mm + 1250mm = 1365mm equivalent, not 5980mm equivalent!

Alf, you really need some lessons in physics. It's pretty obvious that you don't understand digiscoping at all. You don't determine an equivalent focal length with an afocal system by adding the focal length of the tube to the focal length of the camera. You "multiply" the focal length of the camera by the magnification "power" of the telescope. The magnification power of the telescope is determined by both the focal length of the eyepiece and the focal length of the tube. The Meade ETX-90 with a 52x eyepiece yields 5980mm with a 115mm focal length camera in front of it (115 x 52 = 5980mm equivalent 35mm focal length). Precisely it's 5989mm.

Plus you only have 3.1 million pixels to spread that FOV over...Hardly earth shattering resolution!

Then you have the problem of diffraction...The CP990 has an aperture of f4 at 115mm and the Meade has a fixed aperture of f13.8...f17.8 will give major diffraction softness, especially on a camera with 287 pixels/mm.  So not supprisingly, your pic looks very soft.

No Alf, it "doesn't" look "very soft" at all... in fact it's quite sharp and it doesn't have the nasty sharpening halo your pigeon shot shows.

Fit that Meade on a Sigma DSLR and that would be far more interesting...I can get sharper bird shots than yours with only 230mm equivalent on my SD14:

Alf, I've been digiscoping for over 16 years. I'm "totally" familiar with the use of all types of cameras with all types of telescopes. Now take me a photograph at nearly six thousands mm equivalent focal length and then you can compare it to the one above at 5989mm...

Best regards,


100% crop:

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