topic Re: ND filter causing dark images in EOS DSLR & Mirrorless Cameras

EOS 6D Mark II ND filter causing dark images

Skip70 — Wed, 25 Oct 2023 13:58:30 GMT

Canon 6D Mark II

I took some waterfall pics today using a variable ND filer. The ones were dialed in 2-3 stops were fine, but when I went any darker, the photos were very dark, nearly black. I was in Aperture Priority (f5.6 or 6.3), so my understanding is that the camera would read the darker image and lengthen the shutter speed.

As I look at the photos, the few that came out well seem to be around a second or so but the darker ones are all over the map on shutter speed. several at 1/125. It is as if the camera had no idea what to do.

Neither do it, now. Can anyone help?

(I've tried to attaches a couple of samples but they don't upload, even though I reduced them to 600k. I don't seen any stickers on this page on how to upload photos.)

Re: ND filter causing dark images

deebatman316 — Tue, 24 Oct 2023 23:46:18 GMT

If you have a Google/ Gmail Account you can share them on Google Drive.

Re: ND filter causing dark images

stevet1 — Wed, 25 Oct 2023 01:17:15 GMT

Skip70,

Try this approach and see if it works:

1) Put your camera in Manual Mode

2) Pick an Aperture you want to use to give you the depth of field you want

3) set your ISO at 100

4) Adjust your shutter speed until your meter rests on zero (in the middle).

5) Take a picture and see if you are satisfied with the exposure.

6) Write down your settings.

7) Get a long exposure calculator app for your phone. There's bunches of them out there. I've been using one called Exposure Calculator.

8 Plug in the settings you used for your regular photo, and tell it what Stop ND filter you want to use. The app will tell you what to set for your new shutter speed.

9) Focus before you put on your filter, then take your lens out of Auto Focus, and put it in Manual Focus. Once the filter is on, it might be too dark for your lens to focus.

10) Dial in your new shutter speed, and screw on your filter (assuming you are using one), being careful not to touch your focusing ring)

11) Look at the meter, and if you find that the new shutter speed iis going to underexpose your shot, you can adjust your ISO until the meter zeros out.

See if that works out.

Steve Thomas

Re: ND filter causing dark images

Waddizzle — Wed, 25 Oct 2023 02:03:47 GMT

You are correct! Using Av mode should adjust shutter speed and/or ISO to correct for the light reduction caused by the ND filter.

(I’m assuming that you are using it outdoors on a bright sunny day. ND filters do not work very well when used indoor under standard lighting.)

However, there are other settings that could cause conflicts. Safety Shift is one setting that comes to mind. It is possible to define automatic setpoint limits to shutter speed and ISO.

Re: ND filter causing dark images

Tronhard — Wed, 25 Oct 2023 08:11:42 GMT

Using auto settings has its limitations. Both shutter speed and ISO can be limited within the settings of the camera. For example, if go to the ISO settings and check what the limits are for auto ISO you should see an upper limit. Once that is reached it must try to change the shutter speed, but again that will have limits.

Re: ND filter causing dark images

Skip70 — Wed, 25 Oct 2023 14:38:51 GMT

Yes, that would be the process to do everything manually, but my question is that I thought the camera would/should adjust automatically to whatever actually light was hitting the sensor (as long as those exposures were within the limits of the settings, of course).

Re: ND filter causing dark images

Skip70 — Wed, 25 Oct 2023 14:41:23 GMT

Thanks but as I understand it, Safety Shift if anything would have adjusted to make a proper exposure, not result in a badly underexposed shot.

Re: ND filter causing dark images

Skip70 — Wed, 25 Oct 2023 14:55:27 GMT

I don;'t see where to check the ISO settings on the camera and it is not covered in the manual.

I have several photos that came out okay where the camera registered shutter speeds of around 1/4 of a second or so, but the dark ones all show 1/125th, so the camera was reverting to that for some reason. I woiuld have thought with Safety Shift, it woiuld have correct for a badly underexposed picture. I'm not looking for the camera to correct anything, but still puzzled as to why it would not simply read what was coming in to the sensor and adjusting shutter speed accordingly. Meaning, if I had the ND filter set to 4-5 stops down, the shutter speed should have slowed accordingly.

Re: EOS 6D Mark II ND filter causing dark images

kvbarkley — Wed, 25 Oct 2023 16:01:26 GMT

1/125 sounds suspiciously like a flash-sync shutter speed. Could the camera think you have a flash on it?

Re: EOS 6D Mark II ND filter causing dark images

deebatman316 — Wed, 25 Oct 2023 16:02:32 GMT

Flash Sync on the 6D series is 1/180th sec.

Re: EOS 6D Mark II ND filter causing dark images

Skip70 — Wed, 25 Oct 2023 16:17:57 GMT

Agree but I don’t know why jt would think that. Nothing else changed but me rotating the ND filter.

Re: EOS 6D Mark II ND filter causing dark images

kvbarkley — Wed, 25 Oct 2023 17:01:18 GMT

Thanks, I could not find it in the specs. There goes that theory.