Some cameras have a depth of field preview feature. To understand how it works, you first need to find out what the depth of field is, about this, for example, you can read here.
Depth of Field (DOF)
Modern cameras always focus with maximum aperture. For example, if a standard 18-55mm F / 3.5-5.6 lens is used, then focusing will always be carried out only on apertures from F / 3.5 to F / 5.6 (depending on the focal length). But when shooting (shutter release), such a lens can use a very wide range of aperture values, for example, a standard lens Canon Zoom Lens EF-S 18-55mm 1: 3.5-5.6 IS can shoot at apertures ranging from F / 3.5 - 5.6 to F / 22.0 - 36.0. In this case, when focusing, you cannot see in the optical viewfinder what how will the image obtained when shooting with closed apertures look like from F / 5.6 to F / 36.0. Closing the aperture (increasing the F-number) changes the DOF. Depth-of-field preview is there to see how much DOF will change when shooting with a closed aperture.
Depth-of-field preview is a useful option for macro photography and shooting with high-aperture lenses, where changing the F-number causes a significant change in depth of field. The easiest way to understand how the depth of field preview option works in camera mode is'Aperture Priority (A, AV)'. It is enough to use this function at different values of the F number and observe what is happening in the optical viewfinder (camera peephole). Usually, camera users only notice the darkening of the viewfinder - this is due to the fact that at closed apertures in JVI less light gets in and the subject appears darker. Darkening will not appear in any way on the image that will be taken with the aperture closed, as the camera’s automation will select the correct exposure for the small aperture. But besides darkening, it is worth noting that in JVI there are more and more 'sharp' and 'clear' objects.
On some cameras, a dedicated button may be highlighted for depth-of-field preview. It is usually called 'DOF preivew'. When you press this button, the camera automatically sets the aperture specified in the settings. True, there are certain restrictions, for example, my camera Nikon D700 refuses to function as 'DOF preivew' button when Live View is on. On old and modern film cameras, this button is sometimes called the 'Aperture Repeater', since such a button 'rehearses' the depth of field before the main shooting, because on film cameras you cannot immediately see the finished result. Aperture repeater is available on some older lenses, such as Olympus OM-System G.Zuiko Auto-W 1: 3,5 f = 28mm. On lenses that have an aperture control ring and / or aperture preset ring, a depth of field preview can be done manually using the aperture ring and / or using the preset ring.
Personal experience
I do not use such a preview button. From personal experience, I always know how much the depth of field will increase when closing the diaphragm. And even if I need to look at what happens, I just take a test shot at the aperture value I need and get the result right away. I really don’t like that on many cameras, for example, on Nikon D80 the 'DOF preivew' button is non-programmable. I usually set the 'DOF preivew' button to something more useful. So, on Nikon D700 the 'DOF preivew' button is used for setting auto ISO or flash locks... Many users think that the 'DOF preivew' button on advanced cameras will somehow help improve their photos, but this is very rare. Therefore, when choosing a camera, you should not pay attention to the depth-of-field viewing function. By the way, if the camera does not have such a function, then the depth of field can be very easily viewed using Live View (though not for all cameras), or just take a test shot.
Conclusions
Depth of field preview is a very simple and not always useful feature, especially in today's digital photography world.
Thank you for attention. Arkady Shapoval.
P.S. You are welcome, support my friend in his work, click "Support" on the right.
really not a very useful function ... here, in my opinion, what is needed and what is not: http://i-hero-in.narod.ru/news/ehrgonomika_zerkalnykh_kamer_nikon_d90_i_d800/2013-07-24-60
“Auto ISO - I don't think the camera knows exactly what I want to achieve.” In fact, the function almost ideally selects the exposure pair (ISO - as the third component) for the "perfect exposure". But learning to use auto ISO is not the easiest thing :)
Well, they showed off and will be ...
This applies to i-hero-in.narod.ru. but only.
“Learn first”, “sharp” and “check” objects. Sorry for the tediousness! Thanks for the educational program for the owners of junior cameras!
Updated
In some situations, closing the diaphragm leads to such a darkening of the image in the OVI that it is almost impossible to see what is sharp and what is not ...
Friend supported and what kind of competition?
As far as I understand, such "troubles" only with OVI. When sighting through the EVF, you can immediately see the depth of field of the resulting image?
Not always. As I pointed out, focusing always occurs with the aperture open, so you can achieve the most accurate focus.
Mirrorless cameras also have such a function, at least in some I saw. But it’s hard to see sharpness there, so I didn’t use it either in NX11 or D90.
Good evening, Arkady, tell me on the Nikon D7000 camera what it is better to configure the function buttons for beginner amateur photographers.
On what you use most often)
At first, I also tried to use the depth of field preview on my D7000, but this function did not take root in practice - the boundaries of the depth of field are not clearly visible in the viewfinder, just an extra gadget. It is better to look at the world through the viewfinder and try to compose the frame. Practice in photography is the best “diaphragm repeater”! :)
“… Nikon D700 refuses to function as 'DOF preivew' button when Live View is on”
- As far as I know, when you enable Live View, Nikon immediately closes the aperture to the previously set value. If you change the aperture in the settings, it will only change when you “flip” the shutter. This, by the way, is connected with the impossibility to change the aperture in the process of filming.
In my opinion a very useful remark!
Thanks to the author and attention to everyone!
Nikon D80 AF lens Nikkor 35-80 1: 4-5 / 6D
when you press the depth of field button in the viewfinder, nothing is visible on any aperture value: ((((is it sad with the camera?
I did not try another lens, because I have the rest of a set of manual optics. fifty dollars autofocus will come on Tuesday I will try on it
Today this button is useful to me, when testing a lens, you can verify that the aperture is working at all values!
Thank you very much.
When buying a camera, I was very worried about the question - what is this button? Then I scored on this, but now I'm so glad to finally find out what this button does)))
Thanks! I set the horizon level in the viewfinder on this button (Canon 6d). Class !!! I like.
When used with some external flash units (for example, SB-700), a number of cameras are capable of triggering modeling light at the touch of a button to view depth of field. With a certain skill, one can understand the degree of casting shadows.
With manual optics, does this function work?
We understand that we are talking about lenses with a jumping aperture. So, if you cannot control the lens iris from the camera (open-close), then you cannot view the depth of field. So it was on my D90 with Helios 81H.
Vooot, and I press this button on Helios 81N / D7000, but I do not observe changes in the viewfinder with a different aperture. Although on the "whale" 18-55, it seems, too, nothing changes. Probably the hole is small)))?
I just wrote how the D90 worked for me with 81H (aperture blinking). On all lenses for which the aperture is set from the camera (fixes, zooms), the button worked. You can make sure by closing the aperture to 16 or more (if possible) - when you press the OVI should darken. If Arkady writes that he is working, then listen to his opinion, he has much more experience. And yes, the function of viewing the depth of field itself is of little use, many do not notice any changes in this sharpness in the OVI at all.
I'm understood, thank you!
Works
Probably if it is with a chip. Yes?
Good day Arkadiy. Say be affectionate chi pratsyuє autofocus on the closed diaphragm with a pressed button 'DOF preivew'
Does not work on my cameras (D80, D300, 450D). Only contrast in Liveview mode.