The lens is at max aperture if it is a native lens, and you're working in an automatic mode.

If you are in FULL manual mode (set ISO, set aperture, set shutter speed), some models will use the set aperture for viewing. That way, you can see the effects of your exposure (and depth of field) and JPEG processor settings in the EVF.

When working with adapters that do not support electronic coupling between the lens and camera, you have to set the aperture manually in most cases. So there is no automatic diaphragm control. Some adapters for Nikon lenses have a ring that you turn to set the aperture. So when you use these, the actual lens aperture is used for viewing and exposure. This limitation is why I never adapted my Nikkor lenses to Micro 4/3. Stop-down metering is a pain in the butt.

This is incorrect. For SLRs and DSLR, where you are viewing the actual light passing through the lens, the design is to keep the aperture fully open and sprung in such a way that when the shutter is tripped the aperture closes down to the desired f-stop.

However, for mirrorless cameras, this is not necessary, as the EVF (electronic viewfinder) can compensate for the lower light coming through the lens. Thus the lenses do not have the "always open" capability. When you stop the lens down to f11, the aperture gets smaller - you just cannot tell in the EVF since it looks the same. This makes the lenses less costly to manufacture, as there is far less mechanical complication.

The subject of filters has surely been around for a long time, but I am a relative new comer as perhaps others might be, so here is a bit of recent experience that I believe is helping me get better pictures.

Initially, I did not use filters on my lenses. Then a number of people pushed me to use UV filters primarily to protect the front element of the lens. So I ended up buying filters for my lenses. I figured they were pretty much all the same so bought cheap ones.

Later I got to thinking on whether there would be a difference in the various brands of filters, so I researched it on the internet. And found this very interesting report:

https://www.lenstip.com/113.1-article-UV_filters_test.html

I read it carefully. Although the report is relatively old now, it certainly seems authoritative and I was impressed. I expect not a lot ha changed on this subject. I am making changes as suggested by the article. Hello Hoya!

Cheers

I am doing stratigraphic field work that requires photographing geologic formations to document formation characteristics for publication & presentations. A widely used method is to take multiple photographs beginning far away to establish context & then moving closer in stages to reveal specific details, with the final photos being taken with a micro lens. My question is what camera body to use for this work. The over riding issue is resolution.

Because many of the locations require considerable hiking, I want to get it right the first time. I am considering 3 camera bodies: 1.) Nikon Df, 2.) Nikon D 810, & 3.) Nikon D 850. The Df has the advantage of size, weight & cost because I can use my existing vintage F2 film lenses. The disadvantage is pixel count. The advantage of the 810 & 850 are pixel count and very high resolution. The disadvantage is that these bodies may require purchasing several new lenses in addition to the bodies to obtain best results.

The incentive for going digital is the ease of manipulating the images & adding labels during post processing. I want to produce a high quality result, but I don’t want to break the bank. Which ever body is chosen, I will use it for future wild Life and landscape photography.

Your advise is appreciated. Thank you.