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Mirror Lockup and sharpness test with Canon 300D

 
 
Siddhartha Jain
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      12-14-2004
Nothing very scientific - just a small test.
http://www.geocities.com/losttoy2000/MLU-Test.html

- Siddhartha

 
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Todd H.
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      12-14-2004
"Siddhartha Jain" <(E-Mail Removed)> writes:

> Nothing very scientific - just a small test.
> http://www.geocities.com/losttoy2000/MLU-Test.html


Wow. Cool. Thanks for doing that.

--
Todd H.
http://www.toddh.net/
 
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Dave knows who
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      12-14-2004

"Siddhartha Jain" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) ups.com...
> Nothing very scientific - just a small test.
> http://www.geocities.com/losttoy2000/MLU-Test.html


On the D-Rebel were you using the timer since you don't have a remote?


 
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Michael A. Covington
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      12-14-2004

"Todd H." <(E-Mail Removed)> wrote in message news:(E-Mail Removed)...
> "Siddhartha Jain" <(E-Mail Removed)> writes:
>
>> Nothing very scientific - just a small test.
>> http://www.geocities.com/losttoy2000/MLU-Test.html

>
> Wow. Cool. Thanks for doing that.


For those of us without time to download the raw data and analyze it
ourselves -- What did you conclude?


 
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Colin D
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      12-15-2004


Siddhartha Jain wrote:

> Nothing very scientific - just a small test.
> http://www.geocities.com/losttoy2000/MLU-Test.html
>
> - Siddhartha


As the owner of a 300D, and considering the Wasia hack, I was very
interested in your test, Siddartha.

I have some downstream questions, though, that you might be kind enough
to answer for the enlightenment of interested people.

1. How rigid was the tripod? Was it lightweight, or a pro or semi-pro
tripod?
2. Was the centre column raised, and/or was it properly tightened up
with the screw?
3. Was the pan-tilt head secure, and was the rotate bearing under the
head tight, to prevent rotary motion?
4. Were the tripod legs firmly set on the ground, with no play where
they support the centre yoke?
5. Were the shots indoor or outdoor? if outdoor, was there any wind?
6. What were the actual shutter speed and aperture settings used, and
was it the same for both shots?
7. Looking at the original images, the blurring seems to me to be more
like slight out-of-focus, rather than camera shake initiated by the
mirror. Was the camera set on autofocus, or was it critically focussed
manually? I presume the lens was the 18-55mm kit lens (which is pretty
good).

Questions 1 to 5 basically ensure that tripod movement is ruled out as a
cause of loss of sharpness; q.6 could be interesting, as higher speeds,
say 1/200 upwards tend to be too quick for the shake to be apparent, and
slow speeds of 1/2 sec or slower tend to mask any movement that might
happen in a 1/10 second or thereabouts.

Question 7 is the most interesting one. If autofocus was used, slight
errors in focussing and refocussing can easily cause loss of definition,
specially with wide-aperture shots. I have found there seems to be some
hysteresis built-in to autofocus systems, to avoid having the lens
constantly hunting for focus. Repeated focussing on a subject without
moving the camera results in the lens stopping at slightly different
points each time. With normal subject matter, depth of field usually
masks any slight misfocus, but when shooting a flat surface where DOF
doesn't apply, slight misfocus can be all too apparent.

I mention all of this because, as I said in q.7, the blur looks very
much like out-of-focus blur, and not like the blur one gets with camera
movement - a sharp image smeared in one direction.

Colin

 
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David J Taylor
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      12-15-2004
Colin D wrote:
[]
> I mention all of this because, as I said in q.7, the blur looks very
> much like out-of-focus blur, and not like the blur one gets with
> camera movement - a sharp image smeared in one direction.


That was very much my impression as well.

David


 
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Ryadia
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      12-15-2004

"David J Taylor" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Colin D wrote:
> []
> > I mention all of this because, as I said in q.7, the blur looks very
> > much like out-of-focus blur, and not like the blur one gets with
> > camera movement - a sharp image smeared in one direction.

>
> That was very much my impression as well.
>
> David
>

I carried out some intensive focus tests with a 20D and initially got
variable results, thinking it was mirror slap that caused it. later, when I
begain using an extremely ridged mount and an electronic cable release, the
differences were much less.

There is an old established rule of thumb about shutter speed and sharpness
which goes along the lines of 125% of the focal length should be the minium
speed. If you use a 100 mm lens then the shutter speed should be 1/125th of
a second minimum. The longer the lens, the faster the shutter to avoid out
of focus from hand and mirror movement.

When I applied this rule to my tests, there was no focus difference between
mirror up and normal exposures. I suggest the tests this fellow did were in
low light and with slow shutter speeds. These rather than the mirror shudder
itself are probably the cause of the focus variations.

The unclear part of my rule of thumb is with the 1.6 X of DSLRs. Should we
presume a 75mm lens to be 100 for the purpose of that rule? My tests in this
area are inconclusive. None the less, since being more aware of the shutter
speeds, my photographs are much sharper... The resulting shallow depth of
field is OK with some subjects and not with others.

Doug


 
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Siddhartha Jain
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      12-15-2004
Colin D wrote:
> As the owner of a 300D, and considering the Wasia hack, I was very
> interested in your test, Siddartha.
>
> I have some downstream questions, though, that you might be kind

enough
> to answer for the enlightenment of interested people.
>
> 1. How rigid was the tripod? Was it lightweight, or a pro or

semi-pro
> tripod?

Its a light-weight. I bought it for about $25.

> 2. Was the centre column raised, and/or was it properly tightened up
> with the screw?

Yes, the centre column was raised and tightened up well.

> 3. Was the pan-tilt head secure, and was the rotate bearing under the
> head tight, to prevent rotary motion?

Yes, that was secured well as well.

> 4. Were the tripod legs firmly set on the ground, with no play where
> they support the centre yoke?

Yes, it was on a level floor with no play.

> 5. Were the shots indoor or outdoor? if outdoor, was there any wind?

Indoors with not even the fan

> 6. What were the actual shutter speed and aperture settings used, and
> was it the same for both shots?

Yes, both were at:
Focal length: 37mm
ISO: 200
Aperture: f5
Shutter: 1/5 sec

The EXIF info is there in all the photos on the webpage.


> 7. Looking at the original images, the blurring seems to me to be

more
> like slight out-of-focus, rather than camera shake initiated by the
> mirror. Was the camera set on autofocus, or was it critically

focussed
> manually? I presume the lens was the 18-55mm kit lens (which is

pretty
> good).


Good point. I used the "P" mode and AF. Will repeat the test with MF. I
plan to do the test at three different focal lengths and will post
four crops of each, MLU and non-MLU.
Thanks for the input,

Siddhartha

 
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Siddhartha Jain
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      12-15-2004
Dave knows who wrote:
> "Siddhartha Jain" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed) ups.com...
> > Nothing very scientific - just a small test.
> > http://www.geocities.com/losttoy2000/MLU-Test.html

>
> On the D-Rebel were you using the timer since you don't have a

remote?

Duh!! Stupid me ... will definitely keep that in mind alongwith using
MF.

Thanks,

Siddhartha

 
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Michael A. Covington
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      12-15-2004

"David J Taylor" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Colin D wrote:
> []
>> I mention all of this because, as I said in q.7, the blur looks very
>> much like out-of-focus blur, and not like the blur one gets with
>> camera movement - a sharp image smeared in one direction.

>
> That was very much my impression as well.


Actually, my experience in astrophotography is that vibration blur looks
*exactly* like poor focusing and has sent many of us on a wild goose chase
looking for a focusing problem. After all, the camera has several
milliseconds to vibrate in all directions - not just make a single linear
movement - and it blurs the image. So I'll reserve judgment on this. I
agree that the lens needs to be manually focused for the test.


--
Clear skies,

Michael A. Covington
Author, Astrophotography for the Amateur
www.covingtoninnovations.com/astromenu.html


 
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