Why doesn’t the depth-of-field preview button seem to do anything on a Canon 5D Mark II?
Asked 8/4/2017
1 views
2 answers
0
On a Canon 5D Mark II, I tested the depth-of-field preview button in Av and Manual mode at apertures from f/4 to f/22, but I don’t notice any change when pressing it. Is there a setting I need to enable, or could the button be faulty?
Also, I’m confused about what the button is for. When I half-press the shutter, I can already see the scene through the viewfinder (and in Live View/LCD), including what seems to be background blur. So what extra information should the depth-of-field preview button show, and when is it actually useful?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
8y ago
2 Answers
6
With many of Canon's advanced series of DSLRs (e.g. 5D Mark III, 7D Mark II), it would be possible that the Depth of Field Preview button has been remapped to perform some other function.
But the 5D Mark II has no custom function setting in the menu that allows remapping of the DoF Preview button to do something else. When you press the DoF Preview button on a 5D Mark II, there's only one thing it should be doing: stopping down your lens to the selected aperture.
Here's how to test to see if the DoF Preview button is doing anything:
- Set the camera to Av or M exposure mode.
- Set the aperture to the narrowest setting (largest number such as f/22 or f/32).
- Turn the camera around and look in the front of the lens.
- Hold the camera towards a source of light so that you can see the light shining into the viewfinder opening, through the prism and focusing screen, and reflecting off the mirror and out the front of the lens.
- While looking at the entrance pupil (the aperture diaphragm as it appears through the front of the lens) press the DoF Preview button.
- You should be able to see the diaphragm move and the entrance pupil get smaller.
If you don't, then the DoF Preview button is not working properly.
As several comments to the question have mentioned, the effect can be subtle, especially if you are in a very bright light environment and your pupils dilate to compensate for the dimmer viewfinder through which you are looking when the button is pressed. There will probably be very little detectable difference at all between apertures wider than f/2.8 or so, as the viewscreen/focusing screen between the mirror and the prism effectively 'cuts off' at around f/2.8.
From the question and some of your comments it almost seems like you expect something to light up in the display showing you what is in focus and what is not in focus. This is not the case. The DoF Preview button just stops down the aperture diaphragm of the lens and you should be able to see a deeper depth of field by looking at the various areas of the scene itself.
Originally by user15871. Source · Licensed CC BY-SA 4.0
user15871
8y ago
0
Generated from our catalog & community — verify before relying on it.
On the 5D Mark II, the DOF preview button should simply stop the lens down to your selected aperture; there’s no menu setting to remap it. To test it, set Av or M, choose the smallest aperture (for example f/22), and look into the front of the lens while pressing the button. You should see the aperture blades close. If they do not, the button or lens/camera communication may be the issue.
Why you may not notice much through the viewfinder: a DSLR normally keeps the lens wide open for a bright viewfinder image and only stops down for exposure. The DOF preview button temporarily stops it down so you can judge how much of the scene will appear acceptably sharp. The effect can be subtle in the optical viewfinder, especially on a full-frame camera, in dim light, with short focal lengths, or if your focus distances don’t create an obvious change.
A half-press of the shutter does not normally stop the lens down; it just meters/focuses. In Live View, however, the camera may simulate or show exposure/depth changes on the LCD, which can make the DOF button seem less necessary.
Recommended products
UniqueBot
AI8y ago
Your Answer
Related Questions
How do I use the depth-of-field preview button on a Nikon D90?
Why won’t the AF point selection button work on a Canon EOS 5D Mark II?
Is the Canon 5D Mark II autofocus accurate enough for f/1.2 lenses, and is the 5D Mark III better?
Why can’t I change aperture in Manual mode on my Canon EOS 5D Mark II?
Canon FD 50mm f/1.4 aperture linkage is sticky and delays shutter release on AE-1 Program