evening December 16, 2015 time-lapse

I'm trying to understand why the photos strung together shake with telephoto zoom but they do not shake with the fixed focal length lenses. It's frustrating. Come on, help a brother out.

The tripod is cheap, the legs weak, it could be wind, but it's not. Everything is calm. No bouncing children or pets. No disturbance. It is something with the camera or lens.

The thing is, this lens is best one of four for framing the sky. The two fixed focal length lenses cannot get it all, and the wide angle can only get way too much, a third must be cropped to eliminate balconies on each side. Only this lens can frame it just right to get the most end to end without balconies. This lens is the strong preference, but it does this shaking thing.

The camera recalculating aperture is doing it, I think. It changes the whole thing slightly inside. The stack of lenses stay fixed once focused but the aperture at the end of them positioned in front of the sensor changes and that alters slightly how light falls onto the sensor enough to throw off the whole thing ever so slightly and mostly at the edges. 

Visualizing how the stack of lenses will change the appearance of the shapes on the sensor is easy enough, and now visualize how the size of the aperture will do a similar thing. It changes the depth of field. The size of the aperture changes the shapes of things as all these curved surfaces affect light bent onto the sensor. 

Nikkor 18-200

That is a remarkable range when you think about it. It's incredibly difficult to engineer a zoom lens to take good picture at both extremes, but this lens does. That is what is so impressive, great photos at its nearest and its farthest. Not the mind-blowing fidelity and sensual quality of their fixed lenses, nice glints but no sexy bokeh, just good solid reliable photos end to end, even hummingbirds and the like. Not lumberingly slow, but it is not particularly fast either.  

The distance between all the lenses spreads out slightly warping the shape of the image, and so does the size of the aperture stop by stop by stop. 

I talked about this lens before. Now it is giving me this problem. It is an excellent lens. All purpose. It has vibration reduction and extra low dispersion coated glass. Made specifically for DX cameras, 3/4 size of full frame analogous to 35mm. It takes a lot of light to power. The weight of the barrel causes it to drift by its weight, and I noticed that due to it being DX lens for DX camera, made to fit its sensor, that photos definitely vignette, that is darken slightly around all four corners, noticeable when a lot of photos are shown together, they look like the old fashion stick on corners that held photos in albums. This is corrected by batch processing in Photoshop but only in RAW form (NEF for Nikon). Most people set their cameras to shoot in JPG, the cameras convert and  compresses as a matter of internet convenience. The cameras do a very good job of it but the full original load of information captured by the sensor is forfeited. Much more adjustment is possible in RAW.  

The other lenses are made for full frame camera (the old 35mm size). This camera is smaller so the lenses are oversized, too wide. They screw on just fine but the outside area of the lenses are wasted on my smaller sensor. As if the photos are pre-cropped. I'm eager to see what these lenses can do on a full frame camera and one of the things they will do is produce more vignetting. As it is, all that goes beyond the edges of my camera's sensor. 

So, now the problem is identified, the aperture changing is messing things up. Therefore the aperture will be fixed too. No more widening of the pupil so to speak. That will stay the same and the camera will calculate shutter speed for its only variable.