DOF- why do I only get a key-press preview?

Started 5 months ago | Discussions
BigBrother70 Forum Member • Posts: 90
DOF- why do I only get a key-press preview?

Hey all. New M50 owner here. I was pretty surprised to find, after a few first shoots, that the f/stop's effect on DOF wasn't being shown in the preview display. I asked on here and elsewhere and found that I could set a button to preview it, which I summarily did. But I'm still disappointed and a bit baffled by all this...

1. Why wouldn't the camera always be showing this to begin with? Exposure and focus, two obviously critical factors to a shot, are always updated to show me what I'll be getting, so why not DOF as well?

2. The camera is obviously capable of doing this. In the Scn mode, I can adjust "background blur" (I assume a hybrid setting that adjusts your f/stop while adjusting ISO, exposure adjustment, and/or shutter speed to keep exposure fixed) and the final result is permanently shown. I can then walk around, point, and shoot seeing the actual DOF level that will result. (But I don't want to use this mode as I need more control.)

Basically this all just seems... weird. DOF is quite important to the shot and yet it's A) completely hidden from view by default, B) only viewable in a temporary fashion when it is enabled, and C) deemed important enough to be solved for all these only in a beginner mode.

Erg?

Thanks all!

Canon EOS M50 (EOS Kiss M)
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Sittatunga Senior Member • Posts: 2,729
Re: DOF- why do I only get a key-press preview?
1

BigBrother70 wrote:

Hey all. New M50 owner here. I was pretty surprised to find, after a few first shoots, that the f/stop's effect on DOF wasn't being shown in the preview display. I asked on here and elsewhere and found that I could set a button to preview it, which I summarily did. But I'm still disappointed and a bit baffled by all this...

1. Why wouldn't the camera always be showing this to begin with? Exposure and focus, two obviously critical factors to a shot, are always updated to show me what I'll be getting, so why not DOF as well?

2. The camera is obviously capable of doing this. In the Scn mode, I can adjust "background blur" (I assume a hybrid setting that adjusts your f/stop while adjusting ISO, exposure adjustment, and/or shutter speed to keep exposure fixed) and the final result is permanently shown. I can then walk around, point, and shoot seeing the actual DOF level that will result. (But I don't want to use this mode as I need more control.)

Basically this all just seems... weird. DOF is quite important to the shot and yet it's A) completely hidden from view by default, B) only viewable in a temporary fashion when it is enabled, and C) deemed important enough to be solved for all these only in a beginner mode.

Erg?

Thanks all!

It's traditional. Every Canon SLR since 1959 has done this (I'm not sure that all of them even had a DOF preview), every Canon DSLR and every Canon mirrorless camera with interchangeable lenses. SLRs do this so you can see what's going on through the viewfinder when you're using an aperture like f/11. It's also easier to focus a lens when it's wide open (unless the focus shifts significantly when you stop down) and also means that Canon don't have to amplify the viewfinder feed so much most of the time.  It's not as if you can focus critically on a 3" screen or through a viewfinder without focussing aids anyway.

Zinch Regular Member • Posts: 290
Re: DOF- why do I only get a key-press preview?
2

BigBrother70 wrote:

Hey all. New M50 owner here. I was pretty surprised to find, after a few first shoots, that the f/stop's effect on DOF wasn't being shown in the preview display. I asked on here and elsewhere and found that I could set a button to preview it, which I summarily did. But I'm still disappointed and a bit baffled by all this...

1. Why wouldn't the camera always be showing this to begin with? Exposure and focus, two obviously critical factors to a shot, are always updated to show me what I'll be getting, so why not DOF as well?

2. The camera is obviously capable of doing this. In the Scn mode, I can adjust "background blur" (I assume a hybrid setting that adjusts your f/stop while adjusting ISO, exposure adjustment, and/or shutter speed to keep exposure fixed) and the final result is permanently shown. I can then walk around, point, and shoot seeing the actual DOF level that will result. (But I don't want to use this mode as I need more control.)

Basically this all just seems... weird. DOF is quite important to the shot and yet it's A) completely hidden from view by default, B) only viewable in a temporary fashion when it is enabled, and C) deemed important enough to be solved for all these only in a beginner mode.

Erg?

Thanks all!

The reason is that the apperture blades don't close until you take the picture.

I guess they don't close to allow more light to the sensor, easier autofocus and better view to the evf and lcd

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DjangoChained Forum Member • Posts: 54
Re: DOF- why do I only get a key-press preview?

I think all cameras behave like this, not only Canon's.

It has to do with how (D) SLRs work. Firstly, if you close the aperture blades, the view in an optical view finder gets dark and difficult to see. (a problem MILCs with EVF do not have).

Moreover SLRs need much more light for autofocus. The new Canon MILCs can autofocus down to f/22, but DSLRs cannot. I believe Canon has never released an autofocus EF mount lens with an aperture smaller than f/5.6 for that reason.

Lenses like the RF 800 f/11 are only possible on mirrorless.

OP BigBrother70 Forum Member • Posts: 90
Re: DOF- why do I only get a key-press preview?

But this is what makes no sense- most of these explanations are technical reasons for why it's not possible or desirable. BUT, in Scn mode on the camera, it literally does it. You go to a setting called "Background Blur" and adjust it, and you hear the lens changing aperture and the display shows the resulting DOF- not temporarily, it just shows it. As mentioned in my original post, it probably is adjusting all the various exposure params to account for the change in light, as the final image it's showing has the same brightness. In other words, they give you this "user friendly" setting to adjust background blur. So the whole system is obviously completely capable of permanently displaying the DOF.

DjangoChained Forum Member • Posts: 54
Re: DOF- why do I only get a key-press preview?

Well.... Yes. The technical reasons I mentioned mostly pertain to DSLRs, not mirrorless cameras. I guess on the M50 they do it for historical reasons, or some other reason I'm unaware of.

quiquae Senior Member • Posts: 2,013
Re: DOF- why do I only get a key-press preview?
2

BigBrother70 wrote:

But this is what makes no sense- most of these explanations are technical reasons for why it's not possible or desirable. BUT, in Scn mode on the camera, it literally does it. You go to a setting called "Background Blur" and adjust it, and you hear the lens changing aperture and the display shows the resulting DOF- not temporarily, it just shows it. As mentioned in my original post, it probably is adjusting all the various exposure params to account for the change in light, as the final image it's showing has the same brightness. In other words, they give you this "user friendly" setting to adjust background blur. So the whole system is obviously completely capable of permanently displaying the DOF.

I do not have the M50, but I do have an M5 and its SCN mode seems to no such thing. It sets the aperture automatically, but that aperture only kicks in when you press the shutter; the focusing and composing are done wide open, for reasons everyone has described. You should look very carefully—I highly doubt the M50 is actually focusing stopped down; it’s may be just showing you DOF previews while you’re selecting SCN modes.

Incidentally, older Sony bodies do focus stopped down, which was causing all sorts of grief for Sony users with AF speed going down, AF-C not even working past f/8, etc., etc. You can search for “Sony a7 focus stopped down” to see the litany of complaints, including on DPR forums.

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