[Edgar_in_Indy]

What struck me in reading this thread is that TV remotes, which are designed to work indoors away from direct sun IR interference, are so much stronger than the Pentax K remote

As someone else pointed out, part of that probably has to do with the bigger batteries. But that aside, I've found the Dish network remotes to be something of a freak of nature in terms of IR strength. It has two good-sized IR bulbs without any cover over them. It almost doesn't matter where you are, which direction you point it, and even whether there is a direct line of site. I have a lot of different electronics remotes, and none of them are anywhere near as strong as the older Dish remotes.

[Edgar_in_Indy]

The Tamron SP 500mm mirror can focus as close as 1.7m (66.7") for a full frame magnification of 1:3 (or 1:2 on crop factor). It makes a very interesting macro lens with unique rendering and safe distance from subjects.

It's not that this Phoenix / Samyang 500mm can't focus close...but some have said that image quality suffers at close distances. I take it that's not the case with your Tamron?

[nater]

The Tamron SP 500mm mirror can focus as close as 1.7m (66.7") for a full frame magnification of 1:3 (or 1:2 on crop factor).

Macro magnification is a ratio on real life size to projected size on the film/sensor. Crop factor has no impact on that ratio.

[demp10]

Macro magnification is a ratio on real life size to projected size on the film/sensor. Crop factor has no impact on that ratio.

I know, but it does affect the composition from the same (minimum) distance. If you plan to print/view the full extent of the captured image on a given size display/paper, the cropped sensor will show a larger object (the telephoto effect of the crop factor).

So for real life situation when you consider the magnification factor of the printed image also, the crop factor acts as a multiplier.

[madbrain]

The Tamron SP 500mm mirror can focus as close as 1.7m (66.7") for a full frame magnification of 1:3 (or 1:2 on crop factor). It makes a very interesting macro lens with unique rendering and safe distance from subjects.

Looks like the Samyang 500mm minimum focus distance is 2.0m (6.1ft, 73"), not all that different.

Rokinon.com | Rokinon 500mm f/6.3 Multi-Coated ED Mirror Lens (Black) - ED500M-B

[madbrain]

As someone else pointed out, part of that probably has to do with the bigger batteries. But that aside, I've found the Dish network remotes to be something of a freak of nature in terms of IR strength. It has two good-sized IR bulbs without any cover over them. It almost doesn't matter where you are, which direction you point it, and even whether there is a direct line of site. I have a lot of different electronics remotes, and none of them are anywhere near as strong as the older Dish remotes.

Are you sure you are using them in IR mode ?
The Dish network remotes do both RF and IR. In RF modes they work from any directionally and through walls.

Many universal remotes have strong IR signals, but they get much larger. I use a Sony RM-AV3000 . It is a huge remote. It uses 4 AA . I would not use it with the camera, except at home.

[Edgar_in_Indy]

Are you sure you are using them in IR mode ?
The Dish network remotes do both RF and IR. In RF modes they work from any directionally and through walls.

Many universal remotes have strong IR signals, but they get much larger. I use a Sony RM-AV3000 . It is a huge remote. It uses 4 AA . I would not use it with the camera, except at home.

Yes, I'm sure. It's remote "1" so it only has IR. I've had Dish for years and years, and have always noticed how strong the IR was, whether it's controlling the Dish receiver, or some other component. My Samsung TV and Sharp Blu-Ray player remotes are both kind of weak, so I always prefer to use the Dish remote to control them since it is much more responsive. Now, if I cover up the IR transmitters with my hand, it doesn't work, but during normal use nothing seems to slow it down.

I have a Universal URC-R6 "learning" remote that has two IR transmitters (one dark blue, the other clear...not sure why), and it is also not as strong as the Dish remote.

The radio control of Dish can certainly be useful in certain situations, but I've always found the IR to be much more consistent. I don't even have the radio antennas on my receivers anymore, since it seemed like my upstairs receiver was getting commands from a neighbor.

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Last edited by Edgar_in_Indy; 07-12-2012 at 06:22 PM.

[vonBaloney]

Are you sure you are using them in IR mode ?
The Dish network remotes do both RF and IR. In RF modes they work from any directionally and through walls.

Many universal remotes have strong IR signals, but they get much larger. I use a Sony RM-AV3000 . It is a huge remote. It uses 4 AA . I would not use it with the camera, except at home.

If you use a single box for TVs in different rooms, the secondary remote will use radio as it isn't even in the same room as the box. But its true -- the IR you can point almost anywhere and the box picks it up.

[chongmic]

Tried all my TV/DVD remotes, none of them works. Sigh... Looks like I need to get a dedicated remote then.

[Edgar_in_Indy]

Tried all my TV/DVD remotes, none of them works. Sigh... Looks like I need to get a dedicated remote then.

Are you sure you had your camera set correctly? I know that on my K-x, even if it was set for remote shutter release, it would not release while the camera was in live view.

[vonBaloney]

Are you sure you had your camera set correctly? I know that on my K-x, even if it was set for remote shutter release, it would not release while the camera was in live view.

Should work in LV -- that's when the remote is most useful really....

[Edgar_in_Indy]

Should work in LV -- that's when the remote is most useful really....

Those are my same feelings, but it didn't seem to be working. Unfortunately I just sold my beloved K-x, and can do no further testing. I will also not be able to do any further testing of the mighty Phoenix / Samyang 500mm until I get a K-30, but that won't happen until somebody buys my Sigma 50-150mm.

[ChopperCharles]

Here's a sample shot from the Tokina, straight out of the camera, no sharpening or tweaking at all.



And here's the same image with a little contrast adjustment, sharpening, and saturation:



Of course, the down side is that's the sharpest shot out of a series of 15 or so. I'm no friend to manual focus...

Charles.

[Ben_Edict]

I agree wtih the observation the mirror lenses on general are mot well optimized for short focus distances. i have the Vivitar-branded version of this same Samyang-made lens, and while it just as lousy as your image shows at diatances under 20 feet or so, it gets very mich better with distance. See the Mirror Lens Club thread for more examples, but here are a couple I've posted before and still have easy access to:

Well, the optical quality "needs" to suffer at short distances - most "mirror" lenses are made that way.

As all lenses, except macros, mirror lenses are optimized for best performance at infinite distances. With "normal" purely refractive lenses, the loss of IQ at near distances is usually not critical, except if you misuse them for extrem close-ups shots with the help of extension tubes or a bellows. If you are lucky, you use a Gauss type lens for this and these can perform nicely even at short distances...

Mirror lenses are very different: There is a well-defined mechanical distance between the primary and the secondary mirror, at which they reach max. resolution and contrast. This distance is very critical. If you increase the inter-mirror distance to focus at a nearby subject, you will loose this optimized distance between the mirrors. The margin for changing the distances between the mirrors is very small and at short focus distance, the optical path is increased beyond these margins. On top, as most mirror lenses use simple spherical surfaces (as most mirror lenses are in fact catadioptric lenses, based on the Maksutov-design) there spherical abberation will increase significantly, when you extend the inter-mirror distance.

There are only a few select mirror lenses, which avoid this problem, namely the Zeiss Mirotars, because they keep the mirror spacing fixed and focusing is achieved via a classical rack and pinion focuser (and the Mirotars are of the Richter-Slevogt design, which offers some advantages over the more common and cheaper to make Maksutovs).

You can usually recognize the design of the mirror lens (or in 95% of all cases the "catadioptric mirror lens") by its max. aperture: Maksutovs commonly have a max. aperture between f/8 and f/11 or even f/16. If you make them faster, the corrector lens in the front becomes too heavy and too expensive and anyway the design reaches its limits. Faster lenses, like the Mirotars need another design. The Mangin mirrors, à la "solid cats" are an altogether different bunch...

Ben

[Edgar_in_Indy]

Mirror lenses are very different: There is a well-defined mechanical distance between the primary and the secondary mirror, at which they reach max. resolution and contrast. This distance is very critical.

Very enlightening...it sounds like you are extremely knowledgeable on the subject. Based on your experience with mirror lenses, would you say that the images I posted of the panda vase at the beginning of the thread are normal for a 500mm mirror lens shooting a subject approximately 12-15 feet away and without a lens hood? Or does it look like the lens is not performing properly?