How can I control the aperture of a Nikon G lens when using extension tubes? [duplicate]

Question

Due to corona lockdown, I'd like to try macro photography. I have two lenses (18–55 and 35 f/1.8) and a Nikon D5300. As I currently do not have the money to buy a real macro lens, I found 3 cheaper ways:

Reverse Ring adapters, extension tubes, and macro filters. I considered building my own extension tube (I found this YouTube tutorial), but the problem is that my lenses don't have manual aperture control. Does that mean that I'm fixed to the smallest aperture? I found some sort of switch on the lens that lets you control the aperture, but it will be hidden inside the extension tube?

Any tips? I couldn't find "real" extension tubes with electric contacts for Nikon, at leat not in my price range. I'm also aware that reverse ring adapters and macro filters exist, but I decided to stick to extension tubes due to the rear element exposed with reversed lens and lower image quality with filters.

Answer 1

In my experience, extension tubes for Nikon (compatible with D70-D90 generation cameras and their lenses, at the least) are quite inexpensive, in the range from $30 to $100 for a set of three (three different lengths, can be combined in any combination). This is because there are no optics in the tubes, just carry-through for the electronic contacts and mechanical actuators.

In more general terms, for mild macro (say, image size smaller than 1:1), you'll always find extension tubes or equivalent to be the least costly and highest quality way to make macro images. They don't degrade image quality (beyond the unavoidable effects of getting outside the design focus range of the lens, an effect that's usually only visible if you enlarge a lot), because all they're doing is extending the normal focusing method of the lens by mounting it further from the film or sensor plane.

As far as exposed rear element with a reverse mount, these also depend on being able to manually control your aperture, so if your lenses don't have a way to manually trigger the lens to close down, you'll have to shoot wide open -- but as I recall, AI lenses do have this capability (I'm not primarily a Nikon user, though I've shot a bit with D70 and D90).

Macro hint: your 35/1.8 will do a better job at macro than your zoom. Primes are generally of better optical quality than zooms (unless the zoom costs what a good used car should), because they typically have four to about eight elements, rather than the dozen to two dozen found in common zooms and can be better optimized for their design focal length and distance.

Answer 2

Macro filters just change how close your lens is able to focus: they provide best value on superzooms where the main lens does all the hard work of magnification but may not be able to focus closely at long focal lengths. Better macro filters are achromats which use multiple elements in order to compensate chromatic aberration.

Extension tubes provide both magnification and close focusing ability at a loss of light (the "magnification" is done by enlarging the imaging circle, of course without corresponding sensor area unless you are using a DX lens on an FX body). The problem with that is that any part of the optical recipe of the lens designed for a particular imaging plane will not work as designed. This can include corrections of spherical aberration and chromatic aberration.

A reverse ring adapter for putting the 35mm on front of your zoom lens could be interesting and should, with both lenses set to ∞ focus, allow for a close, well-compensated image. Expect fighting with depth of focus issues.

Answer 3

I'd go for extension tubes as being the simplest method to achieve this cheaply.

As already mentioned, you can get a set of 3 tubes, totalling 68mm, for around $£€ 30, just so long as you make sure to get the ones with electrical contacts, usually labelled as SF or auto-focus capable.
In practise, you probably won't be able to get your auto-focus to work - the camera tends to get a bit confused - but you will have a working aperture, which is essential.

Your 35mm lens will probably be the best for this, as it's the sharpest, but you will struggle with couple of aspects…

1. if you put all 68mm of extension tube on, your focal length when set to 'infinite' will be very very short, possibly even appearing to be inside the lens, so you will need 2 of the 3 tubes to be able to get back from your subject far enough.

2. You will need a lot of light. There's some complicated maths to work out how much you lose when adding tubes, but just reckon on needing more light or a higher ISO than shooting without them. Additionally, the closer you get to your subject, the more chance you'll be blocking some of that, even with the lens itself.
   The budget way to achieve a reasonably large flat light is a sunny south-facing window & a big white sheet.
   Lights are not cheap. My own macro rig uses 4 of them, at about $£€ 300 each.

3. You will need a tripod. Shooting something tiny from 6" or less & a depth of field measured in tenths of a millimetre makes hand-held a nightmare.

4. You will then find you still get too much camera shake even on a tripod, even with mirror up & release delay, so you will need a remote trigger. You may have got an Infra Red one with your camera, or even be able to hook up your phone - but if you don't, the simplest is a cable-remote, again cheap on eBay, $£€ 10.

5. Then you realise just how short a DoF you get with that setup - you next you'll be looking at focus-stacking software & a macro rail.

and on it goes… Welcome to the world of GAS [Gear Acquisition Syndrome]