gvaliquette Posted June 1, 2015 Share #41  Posted June 1, 2015 Advertisement (gone after registration) ... The inside diameters of the various Waterhouse Stops are centrally located circular openings of various sizes. The appropriate donut is placed in front of the front element to change the F stop to what is required. These were common in 19th Century photography for lenses of that time which did not always have Internally Adjustable Irises.  ...  Hi Michael,  Were the "Waterhouse Stops" clear "filter-like" devices with clear glass and a central opaque "disk" (probable stuck onto the glass)? If so, that would not increase the depth of field, as it would not reduce the diameter of the entrance pupil. In fact, it would reduce the T-stop, not the F-stop. This is what I was referring to in my post (#37). It would have been preferable to reduce the diameter of the entrance pupil by blocking the outside of a mirror lens' field of view: a thin metal disk with a hole in the center would have done a very good job!  Guy Link to post Share on other sites More sharing options...
Advertisement Posted June 1, 2015 Posted June 1, 2015 Hi gvaliquette, Take a look here MR 500 mm Telyt on M. I'm sure you'll find what you were looking for!
Michael Geschlecht Posted June 2, 2015 Share #42 Â Posted June 2, 2015 Hello Guy, Â A Waterhouse Stop is a disc the diameter of the front lens element it is covering. With a hole in the center. Â No glass elements. Â An "F" Stop measures the Mathematical relationship between the length of a lens & its diameter. Â A "T" Stop measures the actual ammount of light transmitted thru a lens system. Â Anything which modifies an "F" Stop will also effect the same lens's "T" Stop. Â Altho not necessarily equally: Â Example: As you close the diaphram of a wide angle lens a number of "F" Stops: Â The "T" Stops might not close as rapidly as the "F" Stops since there was less illumination in the corners of the wide angle lens when it was opened all the way. Â Best Regards, Â Michael Link to post Share on other sites More sharing options...
gvaliquette Posted June 3, 2015 Share #43  Posted June 3, 2015 Hi Michael,  My mistake. I had in mind a disk similar to that that was used with the Thambar, but you are correct: a metallic disk with a hole in the center would indeed reduce the F-stop and increase the depth of field. I am aware of the difference between F-stop and T-stop. Although T-stops are mostly used with high zoom ratio, multi-elements zoom lenses in cinematography, and although F-stops and T-stops and pretty close to each other in still photography, a catadioptric lens is a good example where the T-stop is dramatically lower, due to the centrally located secondary mirror.  Guy Link to post Share on other sites More sharing options...
jankap Posted June 3, 2015 Share #44  Posted June 3, 2015 No pictures, no fun!  My neighbor wanted to know, what this was. It hangs above his garden. It seems to be a birds nest.  About 30 meters, tripod, electronic shutter, 1/800, ISO 872, Ricoh GXR, Leica MR 500. PS sharpening 100/1.5/0  Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members!   According to the user manual of the MR 500 it is necessary to use one filter. I did not notice any difference with/without.  This nest is at a distance of about 50 meters. ISO 951. Margulis: Bigger Hammer (contrast correction), PS sharpening 100/1.5/0    My dogs have eaten the doughnuts, sorry. Jan Link to post Share on other sites Simply register for free here – We are always happy to welcome new members!   According to the user manual of the MR 500 it is necessary to use one filter. I did not notice any difference with/without.  This nest is at a distance of about 50 meters. ISO 951. Margulis: Bigger Hammer (contrast correction), PS sharpening 100/1.5/0    My dogs have eaten the doughnuts, sorry. Jan ' data-webShareUrl='https://www.l-camera-forum.com/topic/244684-mr-500-mm-telyt-on-m/?do=findComment&comment=2827362'>More sharing options...
Michael Geschlecht Posted June 3, 2015 Share #45  Posted June 3, 2015 Hello Jan,  Nice photos.  There seems to be no shortage of donuts in either photo.  Personally, I like them.  It is curious that some people object to mirror lens donuts while appreciating certain types of out of focus images (Bokeh) with refracting lenses:   Even though the refracting lens's out of focus image is as unrealistic a representation of what is actually there as the out of focus image from the mirror lens is.  Best Regards,  Michael Link to post Share on other sites More sharing options...
jankap Posted June 4, 2015 Share #46  Posted June 4, 2015 Hello Jan, It is curious that some people object to mirror lens donuts while appreciating certain types of out of focus images (Bokeh) with refracting lenses:  Even though the refracting lens's out of focus image is as unrealistic a representation of what is actually there as the out of focus image from the mirror lens is. Michael Thanks. Not to speak of what Picasso has produced out of the real world. Imagine, he needed models to produce his nudes. Jan Link to post Share on other sites More sharing options...
CheshireCat Posted June 4, 2015 Share #47 Â Posted June 4, 2015 Advertisement (gone after registration) No pictures, no fun! Â Are these 1:1 pixel crops ? Link to post Share on other sites More sharing options...
jankap Posted June 4, 2015 Share #48 Â Posted June 4, 2015 The pictures are from the DNG originals with the indicated Photoshop treatment. And a JPG size cut for the LUF. No cropping. Â You can have a Dropbox copy. But not until next week, we are in Switzerland at the moment. I have to pay for roaming contracts daily. Contracts for 50 MB (Megabyte!). Jan Link to post Share on other sites More sharing options...
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