My problem is all solved, but I think I have the light off.

Let me explain further. I moved my focus to the back button. In one case is was a difficult focus problem, but I got it focused (night) and then recomposed the photo. When I went to shoot the camera knows it is not focused, even though it is not trying to do so, so it won't fire. You change the release setting (custom menu a2) and now it fires in spite of that.

Second case, I got lazy on a bright day and did not do a depth of field computation, but instead looked at my f stop, decided on a focus point that would get both something close I wanted and infinity too, and winged it. Again, before I changed the release on a2 what I had composed and where the focal point was now didn't compute.

If I had been alert I should have notice that the "in focus dot" in the viewfinder was probably not lit. I do not have to worry about that any more as long as I focus on the distance I really want and then just shoot.

The next project is exposure. I hope I can set my exposure diameter, point carefully at what I want to capture, then half push the normal shutter release to hold that, and recompose and get a shot I want. We will see....

Verified both helpful suggestions in book. Yes it was resetting focus to "release" and learned about the buffer storage. Thank you Klauss and MT shooterl.

I tried that and a search of the entire D750 manual. No results.

On two occasions, one at night and one on a normal sunny day, after focus and I pushed the shutter release the camera would not fire. In the viewfinder, while the shutter release was held down I saw a code of r35 and the other time r12. Anyone else? I had a suggestion that maybe the data cards were bad, but these were two brand new ScanDisk 95x, 32 MB cards and they camera continued to take pictures both before and after I got past several tries at that time.

If you want to store photos locally and not in the cloud, is that a problem?

How about sending someone a jpeg? I presume their storage is proprietary and something else?

Sigma 600 mm Mirror Lens, Cannon EOS mount. $175

Fixed aperture F/8. Like new, used just twice. (I moved to Nikons)

Not identical; the mount is different. It is a full frame lens as the photo store recognized it immediately when he read "Canon AF" and plugged it in to the latest full frame Canon.

May be a different vintage...I will verify AF by going back to store and shooting with it.

UPDATE: Cannon Full frame AF f8 600mm

I just returned from the Photo Store. It turns out this is a Cannon mount, goes right on a full frame camera and is full AF.

I probably should list this for sale in the other section.

I have this 600 mm Sigma Mirror lens I found in my "really old stuff." I presently use a full frame, Nikon D 750 with a 28-300 mm lens.

The question is: is it practical or worthwhile to try and put a mount on this lens to go on the Nikon. I think the lens goes back about 40 years and has a mount for a Konica film camera.

I have printed more than 10 books with Blurb.com, using their "Booksmart" application. This app allows you to make your own layouts and/or modify their layouts which are saved for you. Their printing is good and their service unbelievably quick (as few as 3 days turnaround). You also have 3 levels of paper quality.

Nikon D750
Pocket carry: Nikon Coolpix 300

Wife: Olympus EM-5
back up: FujiFilm Finepix S-100

Is someone going to tally these?

Sounds clever--I like it.

When I go to print photos, can I still use Aperture to "export" the corrected and cropped files to my print programs?

Even with the backup drives, photos stored with Aperature are not viewable without Aperature. Do you "export" the photos as jpeg's so you can see them or is there away to preserve the editing you have done and un-done years later when the storage format Aperature uses is changed? "What" are you backing up?

How did you handle the timing to catch the top?

There is a free smart phone app from Nikon that takes advantage of the D750's built in WiFi that will have the phone act as the trigger. In addition, it also is capable of showing you on the phone, what the camera is seeing. The attached photo was made that way when I tried it out: I moved around till I was in the photo and then triggered the camera.

I think the link is on the Nikon site under the D750. It is also on the Apple download site: free.