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Re: DOF preview in OVFs of DSLRs is crippled

 
 
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      06-18-2008
In article <(E-Mail Removed)>, Alfred Molon
<(E-Mail Removed)> wrote:

> In article <180620081337392681%(E-Mail Removed)>, nospam says...
>
> > no, they don't. two that came up in a quick google search:
> >
> > 97% coverage:
> > <http://www.steves-digicams.com/nikon880.html>
> >
> > 80% coverage:
> > <http://www.dpreview.com/news/0702/07022006_nikonp5000.asp>

>
> All cameras I've so used so far have 100% coverage. Besides, why would a
> manufacturer cut away the borders.


i have no idea why. ask nikon. however, just because a camera has
live view with an lcd and/or evf does not mean it has 100% coverage.

> > it depends on the viewfinder screen. if dof accuracy is important,
> > select a different screen.

>
> Tell me how to change the viewfinder screen on a DSLR.


it depends on the camera. on some, it's designed to be removed, and on
others it takes a little bit of effort.

here's one guide:
<http://www.earthboundlight.com/photo...ocus-screens.h
tml>

and a video:
<http://www.youtube.com/watch?v=3IjSPL584zg>

it was a whole lot easier back in the film days, and with quite a
variety of screens too:
<http://www.mir.com.my/rb/photography...ikonf3ver2/scr
eens/index.htm>

custom screens for dslrs are available at:
<http://www.katzeyeoptics.com/>
 
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Paul Furman
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      06-19-2008
Alfred Molon wrote:
> Ray Fischer says...
>
>>> 2. Mirror slap vibrations: you are forced to use MLU which not all DSLRs
>>> offer. Problem does not exist in compacts...

>> It doesn't exist in SLRs, either.

>
> Then why do some DSLRs have MLU? Besides I saw some sample images,
> with/without MLU where you could clearly see that the image taken
> without MLU was soft.


MLU is only an issue for rather picky shots of a particular type where
you would want the better image of a DSLR anyways. The new live view
DSLRs are of course in MLU mode.

>>> 6. DOF preview being inaccurate anyway for checking DOF

>> That one is completely false.

>
> Completely true. See the link I posted:
> http://www.dphotoexpert.com/2007/09/...lr-viewfinder/


Compacts don't really show much DOF effect except with closeups. Anyways
the advantage of having a crisp real image of the scene to evaluate is
worth such a minor difference. With the P&S I used to come home with
lots of images with bits of garbage and stupid things featured
prominently that I didn't notice because they were just 3 beige pixels
in the LCD.

There are things about live view I like but I wouldn't trade my DSLR for
a camera with the same sensor, mount and only live view. If it was a
good idea someone would have made such a thing... I know there are a few
that come close, the Sigma, Leica, etc but none have been successfully.
It does seem it would be a simple thing to knock the mirror off a DSLR &
keep the interchangeable lens mount but it hasn't been done. It would be
a neat second body option.

--
Paul Furman
www.edgehill.net
www.baynatives.com

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Ray Fischer
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      06-19-2008
Alfred Molon <(E-Mail Removed)> wrote:
>In article <48593a81$0$17227$(E-Mail Removed)>, Ray Fischer
>says...
>
>> >2. Mirror slap vibrations: you are forced to use MLU which not all DSLRs
>> >offer. Problem does not exist in compacts...

>>
>> It doesn't exist in SLRs, either.

>
>Then why do some DSLRs have MLU?


For those rare occasions where it matters.

>> >3. DLSR Viewfinder which could be misaligned with the main sensor
>> >resulting in tilted images. Problem does not exist in compacts.

>>
>> Vastly higher resolution in the SLR's viewfinder.
>>
>> >4. Optical viewfinder not showing 100% of the scene (this is really
>> >pathetic - any camera with live preview shows 100%)

>>
>> NO camera with live preview shows 100% of the scene. They all show
>> very low resolution versions of the scene.

>
>They do. 100% means that they show the whole scene being captured,
>without cutting away the borders.


But with such low resolution that you canot use it for determining
sharpness.

>> >5. Optical viewfinder being too dark if you use DOF preview

>>
>> LCD screen completely unviewable in bright light.

>
>Then use the EVF.


"Optical viewfinder not showing 100% of the scene"

>> >6. DOF preview being inaccurate anyway for checking DOF

>>
>> That one is completely false.

>
>Completely true. See the link I posted:
>http://www.dphotoexpert.com/2007/09/...lr-viewfinder/


Completely false. DOF preview shows you exactly what is coming
through the lens. And no, I am not so gullible as to believe
everything I see on the web.

>> >The only solution to all these problems is to have live preview on a
>> >high res LCD screen or EVF.

>>
>> When you find a camera that has a 6MP LCD screeen you let us know.

>
>1024x768 RGB pixel would be sufficient.


Yeah, people really flock to those 0.8MP cameras.

>Actually, forgot to mention in my previous post that it's a shame that
>DLSRs have no movie mode.


Buy a camcorder.

--
Ray Fischer
http://www.velocityreviews.com/forums/(E-Mail Removed)

 
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Paul Furman
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      06-19-2008
Alfred Molon wrote:
> In article <4859ebe7$0$17189$(E-Mail Removed)>, Ray Fischer
> says...
>
>>> Completely true. See the link I posted:
>>> http://www.dphotoexpert.com/2007/09/...lr-viewfinder/

>> Completely false. DOF preview shows you exactly what is coming
>> through the lens. And no, I am not so gullible as to believe
>> everything I see on the web.

>
> Sure. And those sample images of the chessboard are fakes, right?


It's real, 85mm f/1.2 at close focus is extreme though. At f/2.8 it's a
minor difference if even perceptible.

>>>>> The only solution to all these problems is to have live preview on a
>>>>> high res LCD screen or EVF.
>>>> When you find a camera that has a 6MP LCD screeen you let us know.
>>> 1024x768 RGB pixel would be sufficient.

>> Yeah, people really flock to those 0.8MP cameras.

>
> You can easily zoom into the image on the LCD, even down to pixel level.
> You don't need to see the entire image at pixel level to focus, a small
> part of the image is sufficient.


If you want to work faster or more freely it helps a lot to have the big
picture clear. Even with an f/1.2 lens, it gives a good idea where the
plane of sharpest focus is and with a super fast lens like that, yes,
you just have to imagine a shallower DOF till you see the shot a moment
later. For slow studio work that delay isn't a big deal, for on the fly
shooting you have 'enough' control for most situations.

One case where live view would be nice is when working with a super-fast
lens like that going for the hollywood bokeh circles, then you can
really compose those circles. Or just for setting up in a particular
situation: it is cool to be able to be able to see the real size of
those OOF circles & see exactly how much is in focus and then once
you've got the right settings, you can go ahead & shoot away.

Anyways if you are working at 85mm f/1.2 you *are* using a Canon DSLR,
(or a film camera: that's equivalent to 135mm f/2) or a Nikon 58mm f/1.2
or some other high end solution which is not a P&S fixed lens EVF camera.

--
Paul Furman
www.edgehill.net
www.baynatives.com

all google groups messages filtered due to spam
 
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Chris Malcolm
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      06-19-2008
Alfred Molon <(E-Mail Removed)> wrote:
> In article <(E-Mail Removed)>, Chris Malcolm says...


>> A Sony Alpha 350 has more MP, has some features you claim DSLRs don't
>> have, and doesn't have some of the disadvantages you claim DSLRs
>> suffer from. In other words, like the R1, it's a hybrid monster which
>> depending on your point of view either falls miserably between two
>> stools or navigates interestingly between the Scylla and Charybdis of
>> two ossified camera technologies. It's the sort of camera I can
>> imagine the R1 design team coming up after someone suggested they try
>> again but this time make it a DSLR.
>>
>> What don't you like about the 350?


> I actually ordered the 350 yesterday, only to have my order cancelled 15
> minutes later because they could not deliver.


I was lucky enough to have ordered the last one of a package deal of
the 350 with the Sony version of the 18-250 "surprisingly good" Tamron
zoom. I notice that more of that particular package deal are springing up.

> The 350 is tempting, but it not so suitable for high ISO (800 and
> above). Another thing, the live view is not a direct video feed from the
> main sensor, so there could be misalignments and you can't zoom in down
> to pixel level. It also does not show 100% of the image you capture.
> Nethertheless it's an excellent live view implementation, as phase
> detection AF is enabled all the time.


> The other candidate is the Pentax K20D or its twin the Samsung GX-20.
> Much better body and OVF, and the live view shows 100% and can zoom down
> to pixel level. But the live view is a bit crippled because there is no
> histogram and you can't change the exposure parameters in live view.


> In any case it will be one of these to cameras (the 350 or the
> K20/GX20).


Keep on eye on this Flickr set, where I'll be putting up some
evaluative photographs taken by this combination. Gusty winds and
rain-threatening clouds don't promise much for this afternoon

http://www.flickr.com/photos/chris_m...7605701184485/

--
Chris Malcolm (E-Mail Removed) DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

 
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Tzortzakakis Dimitrios
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      06-19-2008

? "TRoss" <(E-Mail Removed)> ?????? ??? ??????
news:(E-Mail Removed)...
> On Wed, 18 Jun 2008 22:23:05 +0200, Alfred Molon
> <(E-Mail Removed)> wrote:
>
>>In article <(E-Mail Removed)>, TRoss says...
>>> Repeat after me ... DSLRs do not have an EVF.
>>>
>>> If the camera has an EVF, it isn't a DSLR. A camera that has an EVF
>>> has no need for a reflex mirror, which is one defining characteristic
>>> of an SLR camera. The other defining characteristic is a single lens.
>>>
>>> Besides, an EVF would pretty much be worthless for checking DOF. The
>>> size is too small and the resolution is too low.

>>
>>How about a high resolution EVF. Besides, OVFs are the same size as
>>EVFs. If an EVF is too small for checking DOF, an OVF is also
>>
>>
>>> If the DOF preview isn't 100% accurate, and I'm not saying it isn't,
>>> it is close enough to be a useful tool. The DOF markers on some lenses
>>> are useful tools, too.

>>
>>Well, if you look at the images of the chessboard on that page you'll
>>see that the difference in DOF between what appears in the OVF and the
>>final image is huge.

>
> Fine. You're convinced it isn't accurate and that inaccuracy is a big
> problem and a deficiency. I think it is accurate, or at least accurate
> enough to be useful.
>
>>> >1024x768 RGB pixel would be sufficient.
>>>
>>> For composing, sure. It wouldn't be sufficient for manual focusing.

>>
>>It would, because you can zoom into it, even down to pixel level if
>>necessary. Actually I'm quite sure a zoomable 640x480 LCD would suffice
>>to precisely set manual focus and DOF.
>>
>>> And it would be pretty much worthless in bright light.

>>
>>I've been using camera LCDs in any lighting condition on a variety of
>>cameras and can tell you that LCDs are very usable even in bright light.
>>
>>> DSLRs do not have a "movie mode" because, Survey Says....
>>>
>>> 1. DSLRs have a mechanical shutter
>>> 2. DLSRs have a reflex mirror
>>> 3. DLSRs can't capture images at 24 fps
>>> 4. DLSR sensors don't have video out
>>> 5. There is no place to put a microphone
>>> 6. That's what a camcorder is for
>>> 7. Camera makers are holding back the technology to protect camcorder
>>> sales

>>
>>It seems that you missed all the advances in camera technology of the
>>last few years.

>
> And you seem to be obsessing about a couple of characteristics of
> DSLRs you find objectionable.
>
>>There are now several DLSRs with sensors capable of life
>>view - just lift that mirror up. There are even things called
>>"electronic shutters".

>
> I don't see electronic shutters replacing curtain shutters in DSLRs
> any time soon. If at all. The biggest reason is shutter lag. Smear and
> bloom are two other problems that would have to be addressed.
>
>
>>Your objection Nr. 5 "There is no place to put a microphone" is
>>incredible. No space for a microphone on a huge DLSR, but enough space
>>on a tiny compact?
>>
>>> Also, consider the lifespan of a mechanical shutter is around 100,000
>>> actuations. At 24fps, you would get about 1 hour of movie footage
>>> before shutters start to fail.
>>>
>>> And before you go off on another tangent, consider that replacing the
>>> mechanical shutter with an electronic shutter would compromise image
>>> quality. I don't think anyone would find that desirable.

>>
>>Apparently the Pentax K20D has a mechanical shutter and an electronic
>>shutter. With the electronic shutter the K20D is capable of capturing 20
>>images at 1.5MP per second.

>
> In a 6-second burst. And if I'm not mistaken, the K20D is a 14.6MP
> camera. I think reducing it to a 1.5MP camera qualifies as
> compromising image quality.
>
>
> Maybe one day a DSLR will be able to capture live action video. And
> maybe one day a camcorder will be able to produce still images that
> rival the quality of a DSLR.
>

That would seriously compromise either. My camcorder has an 800 kpixel
sensor, which is fine for video, but it's only crappy 640 X 480 stills. My
still camera leaves a lot to be desired on its video capability. And that's
what it should be.


--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
hordad AT otenet DOT gr


 
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Chris Malcolm
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      06-19-2008
Alfred Molon <(E-Mail Removed)> wrote:
> In article <(E-Mail Removed)>, Chris Malcolm says...


>> Keep on eye on this Flickr set, where I'll be putting up some
>> evaluative photographs taken by this combination. Gusty winds and
>> rain-threatening clouds don't promise much for this afternoon
>>
>> http://www.flickr.com/photos/chris_m...7605701184485/


> The rose image looks good. I wonder how it would look with some
> additional sharpening.


The rose was shot from a tripod.

> The experimental upsample is soft. I downloaded it and resized it to 50%
> (back to the original size), applued some unsharp mask and it still
> didn't look crisp and sharp. Did you shoot RAW?


That one was hand held in a rather blustery wind. I'll start shooting RAW
once I've discovered how far the in-camera jpegs can go.

--
Chris Malcolm (E-Mail Removed) DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

 
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Ray Fischer
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      06-20-2008
Alfred Molon <(E-Mail Removed)> wrote:
> Ray Fischer


>> >Completely true. See the link I posted:
>> >http://www.dphotoexpert.com/2007/09/...lr-viewfinder/

>>
>> Completely false. DOF preview shows you exactly what is coming
>> through the lens. And no, I am not so gullible as to believe
>> everything I see on the web.

>
>Sure. And those sample images of the chessboard are fakes, right?


Explain to us how the image seen through the viewfinder of a dSLR can
be different from the image recorded by the sensor given that the
image is produced by exactly the same lens under exactly the same
conditions.

Perhaps your source doesn't realize that there is a DOF button that
lets one stop down the lens. Perhaps he's incompetant. Perhaps it's
just a mistake.

But I don't blindly believe things that make no sense without even a
hint of an explanation. You shouldn't either.

--
Ray Fischer
(E-Mail Removed)

 
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David J Taylor
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      06-20-2008
Ray Fischer wrote:
[]
> Explain to us how the image seen through the viewfinder of a dSLR can
> be different from the image recorded by the sensor given that the
> image is produced by exactly the same lens under exactly the same
> conditions.
>
> Perhaps your source doesn't realize that there is a DOF button that
> lets one stop down the lens. Perhaps he's incompetant. Perhaps it's
> just a mistake.
>
> But I don't blindly believe things that make no sense without even a
> hint of an explanation. You shouldn't either.


The explanation was, that the sensor accepts a ray bundle with a larger
angle than the viewfinder (if I understood the earlier commentary
correctly). In other words, once the lens opening gets wider than f/2.8
(or whatever), the viewfinder will show no smaller depth-of-field. On
that particular camera. If you changed the viewfinder things could be
different.

I can't comment if that's right in practice (as I no longer have such
large aperture lenses).

David


 
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Paul Furman
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      06-21-2008
David J Taylor wrote:
> Ray Fischer wrote:
> []
>> Explain to us how the image seen through the viewfinder of a dSLR can
>> be different from the image recorded by the sensor given that the
>> image is produced by exactly the same lens under exactly the same
>> conditions.
>>
>> Perhaps your source doesn't realize that there is a DOF button that
>> lets one stop down the lens. Perhaps he's incompetant. Perhaps it's
>> just a mistake.
>>
>> But I don't blindly believe things that make no sense without even a
>> hint of an explanation. You shouldn't either.

>
> The explanation was, that the sensor accepts a ray bundle with a larger
> angle than the viewfinder (if I understood the earlier commentary
> correctly). In other words, once the lens opening gets wider than f/2.8
> (or whatever), the viewfinder will show no smaller depth-of-field. On
> that particular camera. If you changed the viewfinder things could be
> different.


That might be part of it, the part I understand is that the screen is
only partially translucent so some of the image comes through. It's
awkward to explain... if instead of a ground 'glass' focusing screen, if
you had an opaque white projection surface and looked at that from the
other side, that should look correct but you see that image combined
with a clear view from your eye and your eye has a much smaller sensor
than a DSLR (well the part used for viewing in this case anyways). Maybe
I'm missing some terminology, the opening in your eye is much smaller
than the 42mm opening in a DSLR so it's not capable of using the wider
angle rays. It's like holding a video camera up to a DSLR lens, you
won't get the shallow DOF so people invented a device that projects the
lens image onto ground glass and the video camera focuses on the ground
glass rather than focusing on infinity. Sorry, I know I haven't
explained very clearly.

> I can't comment if that's right in practice (as I no longer have such
> large aperture lenses).



--
Paul Furman
www.edgehill.net
www.baynatives.com

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