When doing long exposures with the Tamron 17-28 how do I lock focus before putting my nd filter on?

Use the settings that will give you the best exposure / shutter speed / focus

There are three things you have to consider when getting lenses for the D3200.

First, you already know that the lens has to have the Nikon F mount.

Second, in order to autofocus, the lens must have a focus motor since the D3200 doesn't have one itself. Sigma designates lenses with the focus motor as HSM. Tamron designates theirs as USD. Lenses that don't have the focus motor will still work with the D3200, you just have to focus manually.

Third, the lens must have the electronics to communicate with the camera in order for the exposure meter to work. Any Sigma or Tamron lenses designed for digital cameras will have the electronics. Older mechanical lenses, including those from Nikon, will still work with the D3200, but you must set the exposure manually, without any help from the camera's light meter.

I checked the Tamron website menu of manuals and one is not listed. This is a pass-thru device, so other than placing it between your lens and camera body, there should be no additional settings. Your camera focus and exposure is thru the lens so the camera should adjust seemlessly. Please tell us what the problem is, what lenses and body you are using.

If that is the only lens that you have for that camera, it could be the camera that is bad. There is a sensor in the camera that measures the focus and they do wear out.

This lens lacks the electronics to communicate with the camera. You need to set the aperture to its smallest setting (as you've done) and switch to the manual exposure mode (turn the mode dial to M). You'll get no exposure assistance from the camera's light meter. You can use a separate light meter and/or adjust the exposure by reviewing your pictures.

It's probable that although it's designated Macro, the lens actually only gets in fairly close. I recommend you buy a closeup filter which is a simple lens you screw on the front of your lens. You can different strengths for getting in closer. Otherwise treat yourself to a set of extension tubes which do the same thing but more effectively.
I hope that helps

I don't know your particular mode, but what I do with digital cameras is I use them in the program mode. I then can set the iris priority to under expose by the number of required stops.
On some of the regular cameras, and most high end cameras they have an EV (exposure value) setting. This gives very good control for overall exposer compensation.
If your camera cannot be exposure compensated, you can try putting gel type neutral density filters in front of the flash unit. These come in what looks like a mylar type sheet. They come in different values for density. Normally you would buy a range of values so you can adjust them. I used to buy these from a photo equipment supplier in sheets. I still use these with my digital camera equipment.
You may want to have some in ND-1, ND-2-, ND-3, and ND-4. Then you can use the right combination to find the correct flash exposure you want to use.
You can stick the filter in front of the flash unit and hold it in place with some masking tape.
When using filters in front of the flash, you may have to use the camera in manual mode. This will prevent the automatic mode from over compensating for the change of light from the flash. With this you will have to do exposure tests to find the correct setup.
In the film days, I used to use a flash meter (I still use a flash meter), and calculate the distances and theoretical exposure. Then I would do the tests in a series that I logged on a work chart. After processing, I would see which frame came out properly, and then use the settings as my reference for that photo job.

Jerry G.

Sorry but if you've tried all the usual fixes then there's nothing more that you can do. Either pay for a professional repair or continue to use the lens manually.

A professional repairer should be able to indicate what the likely costs are going to be and you can then judge whether repairs are cost effective.

Personally, I'd stick to manual focus as I've always preferred knowing exactly what I'm focussing on instead of constantly fiddling with buttons and menus to override what the dumb camera has locked onto.

Nothing you can do. The Tamron is not compatable with your camera. So the focus will be slower

You need to do what is called an exposure lock. Aim at the subject, even if it's out of focus and half press your shutter. Then press the * button on the camera (top right) and it will exposure lock. You can then re-focus, but it will hold the exposure that was metered previously, so you'll get focus on a different object to what the camera has focused on. You can exposure lock anywhere, it doesn't even have to be your subject, it could be a nearby window to underexpose, or a nearby dark area to underexpose. Once you've locked the exposure you can focus somewhere else.