MGrayson
Subscriber and Workshop Member
With clean-on-startup sensors I never worry about dust. I'm just wondering how often this camera will need checking. I haven't noticed any dust yet, even with the sensor so exposed.
--Matt
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IBIS issue A7II
- Thread starter Viramati
- Start date
--Matt
jonoslack
Active member
HI Matt
I've had some dust, but it seems to have dropped (or been shaken) off again.
jonoslack
Active member
No - I've not run the cleaning cycle. To be honest I'm careless about mucky sensors. If it bugs me I clean them, if it doesn't I leave them. It seems to me that new cameras always attract more of it though.
MGrayson
Subscriber and Workshop Member
I experimented, and you CAN do the following:
1) With the power on and an OSS lens mounted, start to remove the lens, turning it part way.
2) Turn the camera off. This is probably dangerous and foolish.
3-5) Finish removing OSS lens. Attach adapted lens. Power on.
Or you can just leave the camera on, which is what I will try to force myself to do.
Best,
Matt
1) With the power on and an OSS lens mounted, start to remove the lens, turning it part way.
2) Turn the camera off. This is probably dangerous and foolish.
3-5) Finish removing OSS lens. Attach adapted lens. Power on.
Or you can just leave the camera on, which is what I will try to force myself to do.
Best,
Matt
Annna T
Active member
This may be of interest to some of the followers of this thread :
The Phoblographer has made a comparison of the five axis IBIS in both the Olympus OMD and the SONY A7II :
A Comparison of How Olympus and Sony's 5 Axis Stabilization Work
The Phoblographer has made a comparison of the five axis IBIS in both the Olympus OMD and the SONY A7II :
A Comparison of How Olympus and Sony's 5 Axis Stabilization Work
k-hawinkler
Well-known member
Many thanks. Very illuminating comment by Steve Jones (ignoring the typos).
Summing up, as I understand his post:
Roll stabilization: -
Pitch and Yaw stabilization: lens focal length required.
X and Y stabilization: lens focal length and subject/focus distance required.
However, contribution of X and Y stabilization goes to zero as ratio of focal length over distance goes to zero (or ratio of distance over focal length goes to infinity).
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hodad66
Member
This has all been very interesting reading. I just got my first Sony lens,
a used 70-300G and the LA-EA4 mount & how wonderful it is! With 2 A7's
I was looking for a shorter, faster lens to use as my 500 sits on the other.
I was looking at the 70-400 but thought that I would go cheaper first. I
only tried it in the front yard but the 5 axis is quite nice.
a used 70-300G and the LA-EA4 mount & how wonderful it is! With 2 A7's
I was looking for a shorter, faster lens to use as my 500 sits on the other.
I was looking at the 70-400 but thought that I would go cheaper first. I
only tried it in the front yard but the 5 axis is quite nice.
k-hawinkler
Well-known member
A Comparison of How Olympus and Sony's 5 Axis Stabilization Work, Quote:
"Steve Jones
4 days ago - Shared publicly
It's actually a misnomer calling this 5 axis stabilisation. In 3D spare there are only three axis, but there are two types of movement for each. Along the axis (translation) and rotation round the axis. So there are actually six degrees of freedom, and the Olympus and Sony systems compensate for 5 of them (the one that's missing is, of course, movement along the X azis).
A bit of work with some pencil and paper tells you the following :-
roll motion (rotation around the Z axis) does not depend on lens information at all. The sensor just has to move in the opposite sense to the camera body. The degree of blur induced gets larger the further from the sensor centre.
Pitch and yaw (rotation round the X & Y axis) depends only on the focal length and rotation around the axis where they got through the optical centre of the lens. The formula is (near enough)
S = F * sin(A)
where S is the compensating sensor movement, F is focal length and A is the angle of rotation. Note that this is only true for relatively small angles, and it does not compensate for the tilting of the sensor (not too important for small angles). It can be clearly seen that the movement is in direction proportion to focal length, hence IBIS has more trouble with longer focal lengths. Given that there's not much image circle to play with on an FF E mount lens, the sensor probably can't move more than a few mm or the corners will suffer from vignetting. Ultimately OSS may be the way to for for long focal lengths.
For translation movements along the X & Y axis, the sensor movement depends on both focal length and how far the subject is away. One very important thing to note is that translation movement changes perspective, and it's thus impossible to compensate for such movement other than at one distance. So a photo with a large depth of field with subjects reasonably close to the camera cannot be fully compensated for (no system can do that).
The formula for the movement required is (again, near enough for most purposes, although there a some more approximations involved) is
S = F x M / D
where S is the compensating sensor movement, F is the focal length, D is the subject distance (from the optical centre of the lens) and M is the movement along the axis. What can be seen from this is that the movement is proportional to the focal length and inversely proportional to the subject distance. The important factor here is the ratio of the subject distance to focal length. By the time the subject distance is 100 x the lens focal length, the compensation required is rather low. With subject distances much more than about 200x focal length, it's insignificant and is, in effect, equivalent to "3-axis" stabilisation.
Note that I've considered the rotational moves around 3 axis through the optical sensor of the lens (as it makes the geometry easy). In the real world, the rotations are almost certainly going to be around axis that are dictated by where the camera is held, but it's easy enough to translate any rotation round a given axis location to a combination of translation and rotation movements at the optical centre.
The upshot of all this? If the subject is close (a few times the focal length), then you really want the full 5 axis stabilisation. For hand-held macro, then it's very important. However, if you are shooting at subjects several tens of focal length distant, then 3 axis is probably going to be very effective. So do a lot of hand-held macro, best have a lens with distance encoding attached.
For longer focal length lenses, IBIS will become less effective (whatever the subject distance). A bit of geometry, and a reasonable assumption about the degree of sensor movement available, shows it should work well enough for lenses of up to abut 400mm provided that you are able to keep the centre spot of the lens within the outline of the moon for the duration of the exposure. (The moon subtends about half a degree). However, don't expect IBIS to work well with video on long lenses."
jonoslack
Active member
This is a wonderful lens and shoots well above it's price - I loved it on the A900, I was considering whether this was a better bet than the 70-210 f4 FE lens, and I'm still wondering!