the DOF preview button

[Rooz]

i don't use this very much. do you guys use it and if so can you give me some situations where it helped you and how you used it ?

:)

[coldrain]

Most people do not use it often. It comes in handy when depth of field actually matters. In macro photography which has a natural shallow depth of field, it can come in handy to check just what actually sort of is still in focus.
But in normal snap shots, out doors scenery and such it does not have that much use.

[jcon]

Ive used it just to see what it does and for me, it didnt do anything. Maybe I am doing something wrong but but it just emits a strobe flash onto the subject. I couldnt see any diffference in DOF with the button pressed, it looked just like it does when I dont press it.

Glad you brought this up Rooz, I have been thinking about starting a thread the past few days:D

[colemanr]

I couldnt see any diffference in DOF with the button pressed, it looked just like it does when I dont press it.

The camera always uses the widest aperture while you're composing the shot using the viewfinder. If you also have the camera set to use the widest aperture for the shot, hitting the DOF button won't do anything useful. As mentioned, the DOF button can be useful if you're using a smaller aperture for the shot (as is generally the case with macro shots).

To see the difference, put the camera in "A" mode and set the aperture to the highest number (smallest opening). Now hit the DOF button and you should see quite a difference. The first thing you'll notice is that the viewfinder gets very dim (which is why you want to compose using a wide open aperture). You should also see that more of the shot is in focus, given that a smaller aperture allows for a greater DOF.

Rob

[Rooz]

rob can you pls expand on that. does it have to be a macro lens to get the use out of it ? i used f1.8 and hit the DOF button and i know the cam is doing something cos i can hear it but i can;t tell for the life of me what the hell it is. i did notice the focus point changed somewhat...maybe thats cos i slightly moved the cam as i was pressing the button though.

[lightinsky]

rooz, try the following,

use f/1.8 and frame a pic and focus on something in the middle such that you get shallow depth of field. make sure you can see some thing in the foreground and it should be blur, the background should also be blur., except the subject you focus on. now, if you press the depth of field button, you'll see exactly the same thing, cos the aperture "shuts down" to f/1.8, which is also the widest and what you see thru the viewfinder when composing the pic.

now crank it up to f/22 for the exact same composition. nothing should change in your viewfinder yet, since the aperture is still at f/1.8.. But u know that f 22 will give you larger depth of field, rendering the foreground and background sharper. try pressing down the depth of field now... everything now turns dark, since the aperture had "shut down" to f/22, ie less light coming thru... it might be too dark to see, but you should see that the foreground and background is rendered sharper, like what you would get in the image after u take the pic.

Thats why is called a DOF preview, it lets you see your DOF before taking the pic, so you know exactly what DOF you'll get/..

hope this was clear..

[Phill D]

Nicely explained guys it was a feature I used to use all the time when I had a film slr many moons ago. I've missed it with my digi P&S lately although as the DOF is wider with them they've not been too bad.

Can I ask a related question do all the new dslr's have the DOF preview button? or are there any of them to watch out for that have left this function off to keep the price down?

[jcon]

They all do NOT have the DOF button. As far as I know all the lower end models dont, although I could be wrong. I know the D50 does not.

[Rooz]

great explanation lightinsky. now i see something happening. thanks !
but tell me...what would be the point of doing that with digital ? why not take the photo, if its too dark then retake it. isn;t it quicker to just take a shitload of photos at difference ap rather than fiddling around with that DOF ?

curious as to what circusmatnce this would come in handy. :)

[coldrain]

Nicely explained guys it was a feature I used to use all the time when I had a film slr many moons ago. I've missed it with my digi P&S lately although as the DOF is wider with them they've not been too bad.

Can I ask a related question do all the new dslr's have the DOF preview button? or are there any of them to watch out for that have left this function off to keep the price down?
Almost all DSLRs have a button to close the aperture to judge the depth of field. I do not know about the different Olypus models (I think they have one but strangely located at the back), but apart from those only the Nikon D50 and D40/D40X lack a DOF function.

great explanation lightinsky. now i see something happening. thanks !
but tell me...what would be the point of doing that with digital ? why not take the photo, if its too dark then retake it. isn;t it quicker to just take a shitload of photos at difference ap rather than fiddling around with that DOF ?

curious as to what circusmatnce this would come in handy.
Rooz, the reason for it has nothing to do with if a photo is too dark or not. It only has to do with judging the depth of field. And this you want to do when the depth of field actually is important in the photo...
If you want a certain area to "be in focus" more or less, you just hit the button, the aperture will get smaller, and yous ee through the lens what the effect of the chosen aperture will be in the photo. If it is too shallow, you at that point choose a smaller aperture setting.

That is a lot more handy than taking a photo, then having to look at the review on the small screen, trying to judge it, having to reframe, adjust aperture, take another photo, taking the camera away again, checking on the review, having to reframe again, and so on.

In most cases, when you have experience, just selecting the right aperture for a certain situation to get the desired effect will do too. But this does require a certain experience, of course.
Only in some situations it is really invaluable.

Take a look at this thread:
http://www.dcresource.com/forums/showthread.php?t=30334

Most shots I chose the aperture for the desired effect from experience. A bit more or less depth often does not matter much. But one photo it did matter, the ladybird shot. So there the DOF button came in handy, and let me know that I had to stop down to f13 to get and the ladybird and most of the daisy in focus for the desired effect.

If I would have had to check that on the display in trail and error the ladybird would already have been out of view on its way down to the grass.

[Rooz]

So there the DOF button came in handy, and let me know that I had to stop down to f13 to get and the ladybird and most of the daisy in focus for the desired effect.

great photo. really really nice.
how did it let you know to stop down to f13 ? :confused: can you explain the process you went thru to get that shot ?

[coldrain]

great photo. really really nice.
how did it let you know to stop down to f13 ? :confused: can you explain the process you went thru to get that shot ?
I first of course noticed the little bug walking around. Had the macro lens already mounted, WB on sunlight, metering on partial (9%).
Metered half way between the rather dark red shield and the white of the flower, set the camera to keep that metering.
Camera was already in aperture priority mode ("Av" in Canon speak, do not know by head which mode that is on Nikon).

So, I changed the Aperture to about f8. I framed the flower the way I AF-ed on the ladybug, framed the flower the way I wanted it while holding the shutter button pressed half way, pressed the DOF button with my left hand (is on left of the lens barrel on my Canon), noticed the depth of field was not big enough (not even all of the bug looked in focus) so I turned the wheel to f13, hit the DOF button again, saw that now the flower too was mostly in focus, took care that the top of the shield was exactly in focus by moving a bit forward of backward and took the shot.

Sounds like a lot, but took about 3 seconds I guess.
The only thing that was "wrong" was that I metered just a touch too much of the white, making the shield a bit too dark. But lifting the "shadows" just a touch in photoshop took care of that. If I had metered for perfect exposure for the shield the white petals would have been more blown out, so it was good in hindsight.

[lightinsky]

Rooz, the reason for it has nothing to do with if a photo is too dark or not. It only has to do with judging the depth of field. And this you want to do when the depth of field actually is important in the photo...


Rooz, just to bring home the point, even though you see in the viewfinder a dark scene after pressing the DOF button at f/22, it'll still turn out to be properly exposed, since the shutter speed will get longer. it gets dark because you're seeing the image "real time" and not enough light comes through per second.


I first of course noticed the little bug walking around. Had the macro lens already mounted, WB on sunlight, metering on partial (9%).
Metered half way between the rather dark red shield and the white of the flower, set the camera to keep that metering.

coldrain, great pic!! but one small qns, when you say partial(9%), you mean center weighted? or spot?

and how do you "know" you had to meter between the dark red shield and the white of the camera? comes with experience??

[coldrain]

coldrain, great pic!! but one small qns, when you say partial(9%), you mean center weighted? or spot?

and how do you "know" you had to meter between the dark red shield and the white of the camera? comes with experience??
No, not center weighted. My 350D has 3 modes. The partial 9% one is like your spot metering, just a bit bigger spot.
Since you have to meter on a midtone "grey" to meter correctly, I knew that the shield itself was too dark to meter on, it would totally blow out the daisy. The daisy itself would of course result in too dark a photo...

When there are no midtones to meter on, and the scene does not ask for another metering method, I just try to average the metering this way between the too light and too dark spots.

[Rooz]

thanks for the explanations.

[Phill D]

Thanks Coldrain that's very helpful & the lack of DoF preview has probably just ruled out the low end Nikons for me. That Lady bird shot was great as were the others in the thread you linked too. I had missed that thread previously. How much of a problem do you think the 9% area metering is vs a true spot mode. It doesn't seem to have caused you any problems in the shots you linked to here?

[coldrain]

If you understand exposure a bit (I am learning still myself) the 9% spot vs 3% spot is not a problem at all. In fact, without knowing what you are doing, the smaller the spot, the worse you can mess up your metering.

I am sure that there are certain situations when a smaller spot comes in handy (when you actually know how to use it), but in the ladybird shot it would have been problematic. The same as that in certain situations the DOF button will come in handy (yet one can do without), and mirror lock up can come in handy (yet one can do without), and exposure bracketing can come in handy (yet again one can do without).

It is personal what is important, and without any previous experience it can be hard to know what features will come in handy in future.

Personally I get by just perfectly with the 9% spot, as you can see from the photos in that thread, where I am playing with light, over and under exposing when needed.

[lightinsky]

Coldrain, thanks for the pointers on the metering.

Been trying to learn how to meter consistently, and been trying to get away from matrix, so that I know exactly how my shots will turn out. As you said, everyone is learning...

I read somewhere that for landscapes, one should generally meter against the sky with spot/center weighted. I was wondering if you found this true in your experience??

Also, you have any views about the Sigma 18-125 f/3.5-5.6 ? I posted somewhere else:
http://www.dcresource.com/forums/showthread.php?t=30288

My concern was barrel distortion on the wide end, but I still want a long range as well.

[Phill D]

Coldrain as you say I guess 9% vs 3% shouldn't make much difference for most shots especially when the photographer can compensate exposure when necessary. Thanks again.

[Geoff Chandler]

Back in my FSLR days I used DOF preview ALL the time.
I am starting to use it again now - but I prefer to use it in conjunction
with manual focus.
DOF is proportionally 1/3rd behind the Point of Focus and 2/3rds in front - so don't go setting your focus at infinity on that landscape with forground flowers shot as you will waste a lot of DOF
I used to moved the point of focus in conjunction with DOF preview to obtain the desired range of 'in Focus' detail
Just my 2 pennyworthy
Geoff