Lenses with variable aperture

[Grandpa Ron]

Let's circle the wagons back around and answer the OPs question. With a modern DSLR and a compatible lens, as already has been stated, the camera will compensate for the what ever zoom value is being used.

Even when I attach my old film camera zoom lens to my DSLR, it will automatically adjust the adjust the shutter speed to the amount of light coming through the lens. Since my old lens is not compatible with the camera, I have to manually focus and set the aperture for the depth of field I want. However if I am rushed, I just set the old zoom lens to f11 aperture and just zoom and focus. The DSLR light metering picks the proper shutter speed.

 

[petrochemist]

Let's circle the wagons back around and answer the OPs question. With a modern DSLR and a compatible lens, as already has been stated, the camera will compensate for the what ever zoom value is being used.

Even when I attach my old film camera zoom lens to my DSLR, it will automatically adjust the adjust the shutter speed to the amount of light coming through the lens. Since my old lens is not compatible with the camera, I have to manually focus and set the aperture for the depth of field I want. However if I am rushed, I just set the old zoom lens to f11 aperture and just zoom and focus. The DSLR light metering picks the proper shutter speed.

That last bit is of course dependent on the camera being able to set fast enough shutter speed etc. It's reminded me of some other fixed aperture lenses that have proved awkward in sunlight - I have a 85mm/2.8, a 50mm/2.8, a 24mm/2.8, a 18mm/2.8 & a 50mm/1.2 all without an iris so they can't be shut down from wide open.
The f/2.8 lenses are just about usable when the sun comes out 1/8000s at ISO 100 is possible on most of my mirrorless bodies, but the f/1.2 is going to be overexposed by over 2 stops, and it doesn't even come with filter threads!

 

[zulu42]

Let's circle the wagons back around and answer the OPs question.

Yes, except the OP shoots in manual and the question is about variable vs constant aperture zoom lenses, not about DSLR light metering and shutter speed in auto modes lol.

 

[petrochemist]

Let's circle the wagons back around and answer the OPs question.

Yes, except the OP shoots in manual and the question is about variable vs constant aperture zoom lenses, not about DSLR light metering and shutter speed in auto modes lol.

The OP uses a Nikon DSLR that offers TTL metering, so even in manual mode the aperture change is easily taken care off.

 

[zulu42]

Agreed. Lots of good information in this thread, albeit mostly irrelevant.

The OP was concerned that if they used a variable aperture zoom lens ( eg an f/3.5-5.6 zoom), while shooting in manual mode, they would have to set the aperture from 3.5 to 5.6 themselves when they zoom.
The answer is "no", because of math - the physical design of the lens (the size of the hole as a ratio to focal length) - which others have described with more knowledge than I can.

Talk of metering has no relevance IMO.

Edit: @petrochemist I don't intend to be argumentative or disrespectful. Most of you guys know more about this stuff than me. I just think the OP's actual question was misinterpreted, that's all.