DSLR viewfinder is like f/2.8

olyflyer said:

Leica must use some sort of focusing mechanism since they have not yet invented the AF. Split image rangefinder works but the drawback is parallax and the inability to use long lenses.

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You can use long lenses on a rangefinder. It just becomes increasingly difficult to obtain accurate focus as focal length increases, because the rangefinder doesn't get any more accurate (it doesn't look through the lens). And even if you can focus perfectly, the shallower depth of field that comes with longer lenses just magnifies any calibration errors in the rangefinder mechanism.

But back to the point - the VF on a rangefinder allows accurate focusing if it's perfectly calibrated, but it doesn't go through the lens, so it won't accurately represent depth of field either.

The real solution is either a focusing screen that does show the shallow depth of field that fast lenses give, or live view.

Tone Row said:

Tone Row said:

...no SLR or DSLR or any other camera can show the true DOF. The only way you can see the true DOF is in a large image, so you need a large LCD to view the live view image instead of the small OVF.

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Sony DSLTs can. Whether one considers them a true camera or not is of course entirely up to the beholder

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All cameras capable of live view can. In addition, all cameras equipped with focusing screens designed to show DOF at f/1.4 can too.

It's just that when autofocus and slow zooms came along, all the camera manufacturers started using focusing screens that gave a brighter image with f/2.8 and slower lenses (basically all zooms at that time), at the expense of not accurately showing depth of field with apertures faster than f/2.5 or so.

Just wanted to mention that thanks to this thread, I remembered to check on focusingscreen.com if they finally had a focusing screen replacement for the D600. I ordered one from them last year, when I was still a pentaxian with my k5, and I have to say that it completely changed my ability to manual focus on fast primes. Not only I used to get perfect focus with no effort, but the experience of doing so made me really love the camera. So when I moved to Nikon, I was quite set back that it didn't seem to be an option on the new cameras.

So, after I checked, I saw that they had two in stock of type S for the D600 (now just one, because I ordered one...). If you do order one, consider the type S (I think is from Canon supplies).

On the pentax, replacing the screen was actually easy, and for what I see on the D600 should just just a tad more complicated.

Thank you again for making me think of it.

Alessandro

onasj said:

onasj wrote:

You can assign one of your Fn/Preview buttons to the "Preview" function, which as its name implies will let you preview your image at the DOF that would result from the current aperture setting.

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Yes you can do this - but the problem is that, due to the optical properties of modern focusing screens, the DOF shown is not accurate with apertures wider than about f/2.8

Truman Prevatt said:

Truman Prevatt wrote:

The only way you will see "true DOF" is focusing on a Fresnel lens focusing screen. Those aren't around any longer in DSLR because we are suppose to depend on AF and ask no questions. Today all DSLR come with cheap imitations of a focusing screen because we don't "need" them.

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I don't think it is a fresnel lens type you need. These too have lenses etched into the screen and the lenses have their own optical properties and change the image. For accurate DOF preview you need a plain ground glass screen then the image is simply being focused on the surface of the ground glass by the camera lens without being manipulated by a fresnel lens or other micro lenses.

Only problem is that the image on a plain ground glass screens looks relatively dim unless you are using a fast lens. This is because some of the light gets reflected back off the surface of the plain ground glass so there is light loss.

Modern day viewfinders don't show DOF very well. Just a simple fact. Try live view, use an app, or take two shots.

Learned something new today...thanks.

Buy a mirrorless and you won't have such problems WYSIWYG!

chlamchowder said:

chlamchowder wrote:

chlamchowder said:

Leica must use some sort of focusing mechanism since they have not yet invented the AF. Split image rangefinder works but the drawback is parallax and the inability to use long lenses.

Click to expand...

You can use long lenses on a rangefinder. It just becomes increasingly difficult to obtain accurate focus as focal length increases, because the rangefinder doesn't get any more accurate (it doesn't look through the lens). And even if you can focus perfectly, the shallower depth of field that comes with longer lenses just magnifies any calibration errors in the rangefinder mechanism.

But back to the point - the VF on a rangefinder allows accurate focusing if it's perfectly calibrated, but it doesn't go through the lens, so it won't accurately represent depth of field either.

The real solution is either a focusing screen that does show the shallow depth of field that fast lenses give, or live view.

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I know. Never the less, I have never seen anyone with a long lens using a Leica. It is kind of pointless, even if tecnically possible to shoot, focusing without actually knowing where the focus area ends up in the image is pointless. Of course, there is other possibility, like using the turret view finder, but you have to find one for each focal length, so it isn't practical. This is a huge drawback of rangefinders.

smallLebowski said:

smallLebowski wrote:

Buy a mirrorless and you won't have such problems WYSIWYG!

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But then you get a whole host of other problems, like poor battery life and unreliable AF tracking.

chlamchowder said:

chlamchowder wrote:

chlamchowder said:

smallLebowski wrote:

Buy a mirrorless and you won't have such problems WYSIWYG!

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But then you get a whole host of other problems, like poor battery life and unreliable AF tracking.

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Not really. There is no connection between unreliable AF tracking and mirrorless. It can be made to work and in fact the V1 is faster than most DSLRs in tracking. Reliablility of AF is normally better in mirrorless since CDAF is more accurate than PDAF. "Poor battery life" depends on the camera and the battery and is also not directly related to mirrorless. Some DSLRs have very poor battery life also.

olyflyer said:

olyflyer wrote:

olyflyer said:

chlamchowder wrote:

olyflyer said:

smallLebowski wrote:

Buy a mirrorless and you won't have such problems WYSIWYG!

Click to expand...

But then you get a whole host of other problems, like poor battery life and unreliable AF tracking.

Click to expand...

Not really. There is no connection between unreliable AF tracking and mirrorless. It can be made to work and in fact the V1 is faster than most DSLRs in tracking. Reliablility of AF is normally better in mirrorless since CDAF is more accurate than PDAF. "Poor battery life" depends on the camera and the battery and is also not directly related to mirrorless. Some DSLRs have very poor battery life also.

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Using an electrical screen (EVF, LCD, ...) will always use more power than using an optical viewfinder, everything else being equal. Just because some DSLRs have very poor battery life doesn't mean they would have better battery with an electronic screen (it would be worse, I think ).

I can look through my camera's OVF for days without the battery dropping any more than if it would be switched off. Can't say the same for a mirrorless camera.

olyflyer said:

Not really. There is no connection between unreliable AF tracking and mirrorless. It can be made to work and in fact the V1 is faster than most DSLRs in tracking.

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There is, because mirrorless cameras cannot use a separate PDAF sensor. With regards to the V1, it can't use its on-sensor PDAF system in anything worse than a cloudy day. That's a pretty harsh limitation. DSLRs can keep tracking action with decent reliability even in dimly lit rooms. Also, no one has tested the V1 with a 111mm f/1.2 lens, which would give similar depth of field to a 300mm f/2.8 on a full frame camera. I suspect it's PDAF tracking capabilities aren't that good, and are just being covered up by that camera's huge depth of field.

With the V1 and one of its lenses that are at f/5.6 at 110mm, you have more depth of field than a 300mm f/2.8 stopped down to f/11. And at f/11, I bet I can land a good number of adequately sharp shots on a moving subject without even being in AF-C mode.

olyflyer said:

Reliablility of AF is normally better in mirrorless since CDAF is more accurate than PDAF.

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DSLRs can use CDAF too, when speed is not essential and accuracy is more important. But let's keep this on topic. We're already off topic.

olyflyer said:

"Poor battery life" depends on the camera and the battery and is also not directly related to mirrorless. Some DSLRs have very poor battery life also.

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A mirrorless camera is like a DSLR that's permanently in live view mode. Just to generate a preview, it has to have the image processing chain powered up, and backlight a LCD or EVF screen brightly enough to make it visible in daylight. That's a lot of power drain, especially compared to a DSLR, which can give you a preview without even being powered on.

But back to the original point about viewfinders - getting a mirrorless camera definitely isn't the best solution. After all, your DSLR already has a mirrorless camera inside it, accessible by hitting the live view switch. People buy mirrorless cameras when they're willing to sacrifice performance for a more compact package that still gives similar image quality.

Awesome thread you guys.
Now I seem to have a "problem" and I am curios if it's actually a PROBLEM or this is "normal" due to the reasons you wrote about here.
I have a Nikon D3 and when used with a Sigma 35mm 1.4 lens ( which I love btw ) - I seem to get an out of focus image in the VF - but the focus system is spot on and the image is sharp as it should. First of all - I made the dioptry adjustment right because the info on the internal lcd in the VF looks sharp, and since I spotted this issue, I've played with that knob like crazy. I don't use glasses, I don't have any problem with my eyes so there's 100% not a problem with the adjustment knob. Now by out of focus I do mean a focus shift issue. It's more obvious when I shoot a subject that's further away from me - let's say 8m - 10m. The camera focuses on the subject but I can see that the subject is slightly OOF and that the area in front of the subject is more in focus. Let me give you an example to be more precise. Let's say theoretically I have my main subject at 10 m away from me. And I have another 2 subjects - one at 8m away and one at 12m - so my main subject is between them. If I use the AF system - set the focus point on the subject at 10m away - in the VF I can see that the subject that's at 8m is sharp instead of the one that should be. Picture turns out fine though. If I switch to MF, and try to focus optically ( ignoring the green dot/arrow aid ) - I get the main subject sharp in the VF but when I shoot - the subject at 12m is sharp and my main subject is out of focus. Same thing kinda happens when I use the 85mm 1.4 ( Samyang ) - if I were to go by what I actually see - the photo is OOF by a small margin, but if I were to go with the green confirmation thing, the subject is in perfect focus - although in the VF things looks slightly different.

So what I actually see is not what the camera's AF system sees. Is this thing adjustable ?

Can I "calibrate" the viewfinder ? Would changing the focus-screen make any difference ?

Is this behavior "normal" ?

C0rnholio said:

C0rnholio wrote:

Awesome thread you guys.
Now I seem to have a "problem" and I am curios if it's actually a PROBLEM or this is "normal" due to the reasons you wrote about here.
I have a Nikon D3 and when used with a Sigma 35mm 1.4 lens ( which I love btw ) - I seem to get an out of focus image in the VF - but the focus system is spot on and the image is sharp as it should. First of all - I made the dioptry adjustment right because the info on the internal lcd in the VF looks sharp, and since I spotted this issue, I've played with that knob like crazy. I don't use glasses, I don't have any problem with my eyes so there's 100% not a problem with the adjustment knob. Now by out of focus I do mean a focus shift issue. It's more obvious when I shoot a subject that's further away from me - let's say 8m - 10m. The camera focuses on the subject but I can see that the subject is slightly OOF and that the area in front of the subject is more in focus. Let me give you an example to be more precise. Let's say theoretically I have my main subject at 10 m away from me. And I have another 2 subjects - one at 8m away and one at 12m - so my main subject is between them. If I use the AF system - set the focus point on the subject at 10m away - in the VF I can see that the subject that's at 8m is sharp instead of the one that should be. Picture turns out fine though. If I switch to MF, and try to focus optically ( ignoring the green dot/arrow aid ) - I get the main subject sharp in the VF but when I shoot - the subject at 12m is sharp and my main subject is out of focus. Same thing kinda happens when I use the 85mm 1.4 ( Samyang ) - if I were to go by what I actually see - the photo is OOF by a small margin, but if I were to go with the green confirmation thing, the subject is in perfect focus - although in the VF things looks slightly different.
So what I actually see is not what the camera's AF system sees. Is this thing adjustable ?

Can I "calibrate" the viewfinder ? Would changing the focus-screen make any difference ?
Is this behavior "normal" ?

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I'm wondering about the highlighted phrase. If you want accurate manual focus, point the camera without a lens on it (and without the body cap on, of course!) at a blank wall, and adjust the diopter knob until the focus brackets (on the viewfinder screen) are as sharp as you can get them. Once done that way, you should get accurate manual focus that matches an accurately focused shot taken with AF.

what happens to DOF when using live view?

The rear viewfinder acts as a second aperture.

If you lay a DX, FX and F100 body face down, no body caps on, on a light box so that light shines through the viewfinder the F100 has the largest apparent viewfinder, FX is in the middle and DX is smallest.

Full frame first, the digital bodies has more negative viewfinder magnification than the F100 and appear smaller.

DX starts by being smaller because of the format, but has negligible minus magnification so is not as small as you might expect.

I make it the F100 does not show dof or extra brightness (using the dof preview) wider than f2.3, the FX bodies wider than 2.5 and the D300/7000/7100 wider than f2.8.

Whether the viewfinder dof at f2.8 and smaller is accurate depends in part on how you crop the image, the scene contrast and the ISO used.

LiveView shows dof even at f1.4, though except with a D800/4 it is not "real time" if you change the aperture. You have to come out of LiveView, change the aperture, and go back into LiveView to compare dof at different apertures with most Nikon bodies.

Borrax said:

Borrax wrote:

what happens to DOF when using live view?

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Live view is your friend when looking for true DOF preview, with the caveat that, on the D600 at least, the aperture doesn't change in realtime in Liveview. My solution is to get a bunch of slightly older, much cheaper D lenses and third party, with aperture rings. Also, for manual focus, get yourself a cheap viewfinder loupe, and the back screen becomes a lot more useable - turn up sharpness settings in picture profile (doesn't affect raw files, just the appearance) and you can use the screen for manual focus with an f1.4 lens without magnification, as the sharp edges will "buzz".

PK24X36NOW said:

PK24X36NOW wrote:

If you want accurate manual focus, point the camera without a lens on it (and without the body cap on, of course!) at a blank wall, and adjust the diopter knob until the focus brackets (on the viewfinder screen) are as sharp as you can get them. Once done that way, you should get accurate manual focus that matches an accurately focused shot taken with AF.

Click to expand...

Thanks for tip. I didn't know that!