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Author Topic: Mirror Bounce 500cm  (Read 4793 times)
Terence h
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« on: December 14, 2006, 08:38:18 AM »
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Hello all i have a Hasselblad 500 cm and using a Leaf Aptus 22 last weekend i noticed that when i did not use mirror lock up at slow speeds and sometimes not so slow speeds the mirror bounce was very apparent.
Is the 503CW better in this respect, because it is going to be nearly impossible  to photograph people at slow speeds having to lock the mirror up for every shot on location.
My Aptus 65 arrives soon and i would like to use it as much as possible, rather than switching to my
35mm dslr for low light.
Or maybe i will have to wait until i upgrade in a year or so to switch bodies to a camera less clunky in handling.

Regards
Terence Hogben
Durban
S.A
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Terence Hogben. Durban. South Africa. http://www.terencehogben.co.za
mahleu
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« Reply #1 on: December 14, 2006, 12:50:14 PM »
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HAve you tried using a bean bag on top of the lense to deaden the vibration?

Matthew
White River, SA
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SeanFS
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« Reply #2 on: December 14, 2006, 01:18:56 PM »
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I find the same thing with my ELX but I'm on a tripod most of the time and am able to lock the mirror up easily,  I also see it in my 1ds2 files at anything under 1/30th unless I lock the mirrors up on both cameras. There were a few complaining of the same issue with the H1 a while back but I have seen nothing recently.

Much of that mirror bounce has always been there but hidden by film grain - its much more visible with digital.


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Hello all i have a Hasselblad 500 cm and using a Leaf Aptus 22 last weekend i noticed that when i did not use mirror lock up at slow speeds and sometimes not so slow speeds the mirror bounce was very apparent.
Is the 503CW better in this respect, because it is going to be nearly impossible  to photograph people at slow speeds having to lock the mirror up for every shot on location.
My Aptus 65 arrives soon and i would like to use it as much as possible, rather than switching to my
35mm dslr for low light.
Or maybe i will have to wait until i upgrade in a year or so to switch bodies to a camera less clunky in handling.

Regards
Terence Hogben
Durban
S.A
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marc gerritsen
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« Reply #3 on: December 14, 2006, 01:49:39 PM »
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Hi Terence

Also I am mostly shooting on tripod  and in the event of hand held I really have to use
high speed or mirror lock up. Compose, mirror up and shoot.

Even in my Pentax 67 film days one could detect mirror slap through slight blur.
With digital it is more defined.

Alternatively if you are using a fix lens for shooting people is to attach a "rangefinder
viewer"  to frame your shot and permanently leave your mirror up.
I was considering this as an attachment that could be slotted in my camera flash mount.  

cheers
Marc
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Jack Varney
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« Reply #4 on: December 14, 2006, 01:56:56 PM »
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Mirror induced camera shake can be easily visualized by taping, or rubber banding, a laser pointer to the camera and shining the light on a distant wall (12 feet or so away). Even with the camera on a weighted tripod you will see the laser beam's jitter on the wall when the shutter is fired.
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Jack Varney
nik
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« Reply #5 on: December 14, 2006, 02:50:18 PM »
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Terence, the 503 is no better than what you have for your intended purpose, you will still see bounce on film and more so on digital. I shot the Mavericks contest last year with film and a sinar eMotion22 back, the bounce was apparent, nothing escapes that back. Mirror lockup helps, but I'd suggest you go with your intended plan and switch your gear to something else.

Good to see someone from my hometown on this forum

-Nik









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Terence h
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« Reply #6 on: December 15, 2006, 02:35:02 PM »
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Terence, the 503 is no better than what you have for your intended purpose, you will still see bounce on film and more so on digital. I shot the Mavericks contest last year with film and a sinar eMotion22 back, the bounce was apparent, nothing escapes that back. Mirror lockup helps, but I'd suggest you go with your intended plan and switch your gear to something else.

Good to see someone from my hometown on this forum

-Nik
------------------------------
http://www.stoqq.com
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Thanks  to all for all the shared experiences guys.
Most of my work is still life, so the bounce is not always an issue, but i am even more aware, just how careful we must be with the higher res backs.

Howzit from Durbs Nik.

Regards
Terence
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Terence Hogben. Durban. South Africa. http://www.terencehogben.co.za
Gary Ferguson
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« Reply #7 on: December 15, 2006, 04:38:27 PM »
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Mirror induced camera shake can be easily visualized by taping, or rubber banding, a laser pointer to the camera and shining the light on a distant wall (12 feet or so away). Even with the camera on a weighted tripod you will see the laser beam's jitter on the wall when the shutter is fired.

I completely agree that mirror slap can significantly degrade image quality, and also that this is more apparent with digital than film. However, the laser test doesn't in itself conclusively demonstrate the effect, as the vibration could be caused by the mirror returning; or the laser's wobble may not actually coincide with the actual period of exposure. Furthermore, the vibration may well derive from the shutter rather than the mirror (and focal plane shutters are generally worse than leaf shuuters in this respect), even the friction within a mechanical cable release can impart some degree of vibration into the exposure.

Zeiss's Photographic Lens Marketing Manager once posted an interesting claim that most home grown lens tests designed to explore image quality have limited validity, because unless an impractically heavy tripod is used there'll be some degradation of quality due to vibration even with the mirror locked up.
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howiesmith
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« Reply #8 on: December 15, 2006, 05:22:16 PM »
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I completely agree that mirror slap can significantly degrade image quality, and also that this is more apparent with digital than film. However, the laser test doesn't in itself conclusively demonstrate the effect, as the vibration could be caused by the mirror returning; or the laser's wobble may not actually coincide with the actual period of exposure. Furthermore, the vibration may well derive from the shutter rather than the mirror (and focal plane shutters are generally worse than leaf shuuters in this respect), even the friction within a mechanical cable release can impart some degree of vibration into the exposure.

Zeiss's Photographic Lens Marketing Manager once posted an interesting claim that most home grown lens tests designed to explore image quality have limited validity, because unless an impractically heavy tripod is used there'll be some degradation of quality due to vibration even with the mirror locked up.
[a href=\"index.php?act=findpost&pid=90757\"][{POST_SNAPBACK}][/a]

I think what this means is the effect depends on the frequency and amplitude of the shake comaperd to the shutter speed and where in the shaking cycle the shutter is open.  A good guess is the shaking velocity is greatest when the displacement is zero.  And the velocity is minimum (even zero for a moment as the direction reverses) when the deflection is greatest.  So test results would depend on some factors that are not easily controlled.

It seems to me (and I haven't tried the laser test) that whatever the amplitude of the wiggling laser spot is at 12 feet, it it 10 times that at 120 feet.  Same with the velocity of the spot's wiggle.  How is it ever possible to get a decent image at infinity if mirror slap is such a huge problem?  Could the wiggle at infinity ( or even a mile) be as big as the frame size.  And, using a smaller digital sensor, the wiggle would be an even larger fraction of the frame.
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Robin Casady
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« Reply #9 on: December 16, 2006, 01:06:41 AM »
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I completely agree that mirror slap can significantly degrade image quality, and also that this is more apparent with digital than film. However, the laser test doesn't in itself conclusively demonstrate the effect, as the vibration could be caused by the mirror returning; or the laser's wobble may not actually coincide with the actual period of exposure. Furthermore, the vibration may well derive from the shutter rather than the mirror (and focal plane shutters are generally worse than leaf shuuters in this respect), even the friction within a mechanical cable release can impart some degree of vibration into the exposure.
[a href=\"index.php?act=findpost&pid=90757\"][{POST_SNAPBACK}][/a]
I've used the laser pointer technique to compare a few cameras for use on telescopes. By using Bulb one can look at just the motion caused by mirror up and shutter opening. Then check the effect of the shutter with MLU and Bulb. I've seen some 35mm SLRs with more vibration from the shutter than from the mirror.

I had an early 500cm with a significant amount of mirror slap, visible with film.
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marc gerritsen
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« Reply #10 on: December 16, 2006, 01:27:13 AM »
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the laser test is a neat idea

just tested my H2, had it on a tripod 10m away from the wall and mirror slap

caused the laser point to move about 5mm up and down.

no vibration of the shutter was detected.

I did the test on the tripod not extended and fully extended, which made no difference at all.

cheers
Marc
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Jonathan Wienke
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« Reply #11 on: December 16, 2006, 04:07:50 AM »
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It seems to me (and I haven't tried the laser test) that whatever the amplitude of the wiggling laser spot is at 12 feet, it it 10 times that at 120 feet.  Same with the velocity of the spot's wiggle.  How is it ever possible to get a decent image at infinity if mirror slap is such a huge problem?  Could the wiggle at infinity ( or even a mile) be as big as the frame size.  And, using a smaller digital sensor, the wiggle would be an even larger fraction of the frame.

Howard, you're overlooking some extremely basic geometry here. The angular range of camera motion caused by mirror movement is constant regardless of subject distance. If you have a 2-pixel mirror slap blur on a subject 5 feet away, moving the subject to 500 0r 500 feet away will still give you a 2-pixel blur as long as the camera/tripod/lens setup is not changed. The amount of blur is not related to the absolute distance traveled by the laser spot on the surface of the subject in inches, meters or whatever, but by the angle that linear distance represents to the camera. This will remain constant no matter where the subject is in relation to the camera.

Doubling subject distance doubles the distance the laser spot will move across the subject, but the angle of movement, and the degree of blur that angle represents, is exactly the same.
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howiesmith
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« Reply #12 on: December 16, 2006, 08:33:25 AM »
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Howard, you're overlooking some extremely basic geometry here. The angular range of camera motion caused by mirror movement is constant regardless of subject distance. If you have a 2-pixel mirror slap blur on a subject 5 feet away, moving the subject to 500 0r 500 feet away will still give you a 2-pixel blur as long as the camera/tripod/lens setup is not changed. The amount of blur is not related to the absolute distance traveled by the laser spot on the surface of the subject in inches, meters or whatever, but by the angle that linear distance represents to the camera. This will remain constant no matter where the subject is in relation to the camera.

Doubling subject distance doubles the distance the laser spot will move across the subject, but the angle of movement, and the degree of blur that angle represents, is exactly the same.
[a href=\"index.php?act=findpost&pid=90810\"][{POST_SNAPBACK}][/a]

You are right.  I have forgotten the translational part (up and down, back and forth) which are not a funcrion of distance.  Angular vibrations will be amplified by distance if the camera is at one corner of the triangle.  (Make a triangle taller, the base gets bigger.)  Maybe the fact that distant subjects are not affected more than closer ones says mirror slap is largly translational, not angular.  Thanks.
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Jack Varney
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« Reply #13 on: December 16, 2006, 09:37:04 PM »
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Quote from: Gary Ferguson,Dec 15 2006, 10:38 PM
However, the laser test doesn't in itself conclusively demonstrate the effect, as the vibration could be caused by the mirror returning; or the laser's wobble may not actually coincide with the actual period of exposure. Furthermore, the vibration may well derive from the shutter rather than the mirror (and focal plane shutters are generally worse than leaf shuuters in this respect), even the friction within a mechanical cable release can impart some degree of vibration into the exposure.

Quite right Gary. The test is for illustration only. I found it surprising. With mirror up there is still some shake from the shutter, though much less. I used an electronic cable release to minimize mechanical cable release effects.
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Jack Varney
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