The wrong focal length IBIS

blackest · 08-23-2017, 07:15 AM

With older lenses Focal length isn't communicated to the camera body. Is it possible to make images worse with the wrong IBIS
with say a 35 - 105mm lens if IBIS is set to say 35mm and you zoom to 105mm how negative an effect is that? Is there an improvement or would it be worse than no stabilization at all?

timw4mail · 08-23-2017, 07:20 AM

Originally posted by blackest

With older lenses Focal length isn't communicated to the camera body. Is it possible to make images worse with the wrong IBIS
with say a 35 - 105mm lens if IBIS is set to say 35mm and you zoom to 105mm how negative an effect is that? Is there an improvement or would it be worse than no stabilization at all?

It's fine. Generally the rule of thumb with zooms is to set image stabilization to the low end of the zoom.

Na Horuk · 08-23-2017, 07:41 AM

When you mount a lens that does not communicate focal length, you have to input it by hand. You should input the exact number.
Problem is the numbers you can't input and zoom lenses.
Yes, SR can make pictures more blurry. I think its only when the focal length that you input is higher than the actual one. Then the SR might overcompensate and introduce blur. If the input number is lower, the SR will simply be less effective, but it won't add blur.

With primes, you should input the exact number or the nearest wider number. For zooms people usually input the lowest number they will be using. Some people use 70-200mm zoom only at 200mm, so you can input 200. If you will only use it between 100 and 200, input 100. If you will use it in the whole range, from 70 to 200, then input 70.
OR you can input 200mm and disable SR when you zoom to a lower number, since you might not need SR if you are at 100mm with good light conditions.

On my manual lenses I input nearest wider number. In strong light, I might not even use SR (if shutter speed is really fast).

blackest · 08-23-2017, 07:56 AM

Originally posted by Na Horuk

When you mount a lens that does not communicate focal length, you have to input it by hand. You should input the exact number.
Problem is the numbers you can't input and zoom lenses.
Yes, SR can make pictures more blurry. I think its only when the focal length that you input is higher than the actual one. Then the SR might overcompensate and introduce blur. If the input number is lower, the SR will simply be less effective, but it won't add blur.

With primes, you should input the exact number or the nearest wider number. For zooms people usually input the lowest number they will be using. Some people use 70-200mm zoom only at 200mm, so you can input 200. If you will only use it between 100 and 200, input 100. If you will use it in the whole range, from 70 to 200, then input 70.
OR you can input 200mm and disable SR when you zoom to a lower number, since you might not need SR if you are at 100mm with good light conditions.

On my manual lenses I input nearest wider number. In strong light, I might not even use SR (if shutter speed is really fast).

Thank you both for your rapid replies, so better short rather than long. It's a shame it lives in the menu's, would love it if you could just hit a button and use a command dial. to set focal length I'm starting to add user modes to my camera I mainly use aperture priority with catch in focus on and off I don't know if focal lengths could go in as a user mode. times like this i wish we had a 'magic lantern' for Pentax.

Na Horuk · 08-23-2017, 08:26 AM

Yea, Pentax firmware was really good, but it could use an update with some more user options

Originally posted by blackest

so better short rather than long.

I think so. Only exception is when you are in macro range. Some user did tests that in macro, with high magnification, you can actually use slightly longer for maximum effect. But in macro range you usually use a tripod anyway (and SR should be disabled when using tripod)

pschlute · 08-23-2017, 08:46 AM

Originally posted by blackest

It's a shame it lives in the menu's, would love it if you could just hit a button and use a command dial. to set focal length

On the K1 you can. It is in/can be added to the info menu....accessible by pressing INFO

blackest · 08-23-2017, 10:21 AM

Originally posted by pschlute

On the K1 you can. It is in/can be added to the info menu....accessible by pressing INFO

One more reason to get a K1 unfortunately it's not likely in the near future...

I was experimenting with the user modes on the k5 and found i couldnt use green button metering on a manual mode or at least i couldn't make it work.

user modes do seem to remember focal lengths though which might be handy for ka lenses.

pschlute · 08-23-2017, 10:56 AM

Originally posted by blackest

I was experimenting with the user modes on the k5 and found i couldnt use green button metering on a manual mode or at least i couldn't make it work

No reason why that should be the case..... unless ..... Did you create the USER mode before you changed the menu setting to "enable aperture ring"? The USER mode may still have that setting off

blackest · 08-23-2017, 11:10 AM

Originally posted by pschlute

No reason why that should be the case..... unless ..... Did you create the USER mode before you changed the menu setting to "enable aperture ring"? The USER mode may still have that setting off

Ok that was weird i now have it working

jup · 08-23-2017, 11:59 AM

Originally posted by blackest

One more reason to get a K1 unfortunately it's not likely in the near future...

KP has the same functionality. You can add focal length setting to INFO menu for quick access. I am pretty sure any K-3ii replacement will have that too.

**twilhelm** · 08-23-2017, 01:13 PM

On your original post, if you have the IBIS set too long, say shooting with a 28-105, and have it set at 105 but shoot at 28, you will introduce some blur, especially in any low light situation.
Don't ask me how I know...

dConvert · 08-23-2017, 01:52 PM

The longer the focal length the more the sensor has to move to correct any movement. If the entered value is less than the actual focal length the movements will be in right direction but not big enough to cancel all shake. So a net improvement is seen.
If the focal length entered is slightly too high the sensor will move too much, but may still be an improvement on unstabilsed if the error is not too great.
I suspect if the focal length entered is more than twice the real focal length the corrective movement may become greater than the original shake making matters worse.

I believe the actual relationship will be down to FOV rather than focal length, but why complicate matters!

08-23-2017, 07:15 AM	#1
blackest Senior Member Join Date: Jun 2013 Photos: Albums Posts: 171	The wrong focal length IBIS With older lenses Focal length isn't communicated to the camera body. Is it possible to make images worse with the wrong IBIS with say a 35 - 105mm lens if IBIS is set to say 35mm and you zoom to 105mm how negative an effect is that? Is there an improvement or would it be worse than no stabilization at all?

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08-23-2017, 07:20 AM	#2
timw4mail Pentaxian Join Date: Apr 2017 Location: Driving a Mirage Photos: Gallery \| Albums Posts: 1,670	Originally posted by blackest With older lenses Focal length isn't communicated to the camera body. Is it possible to make images worse with the wrong IBIS with say a 35 - 105mm lens if IBIS is set to say 35mm and you zoom to 105mm how negative an effect is that? Is there an improvement or would it be worse than no stabilization at all? It's fine. Generally the rule of thumb with zooms is to set image stabilization to the low end of the zoom.

08-23-2017, 07:41 AM	#3
Na Horuk Veteran Member Join Date: Feb 2012 Location: Slovenia, probably Photos: Gallery \| Albums Posts: 11,186	When you mount a lens that does not communicate focal length, you have to input it by hand. You should input the exact number. Problem is the numbers you can't input and zoom lenses. Yes, SR can make pictures more blurry. I think its only when the focal length that you input is higher than the actual one. Then the SR might overcompensate and introduce blur. If the input number is lower, the SR will simply be less effective, but it won't add blur. With primes, you should input the exact number or the nearest wider number. For zooms people usually input the lowest number they will be using. Some people use 70-200mm zoom only at 200mm, so you can input 200. If you will only use it between 100 and 200, input 100. If you will use it in the whole range, from 70 to 200, then input 70. OR you can input 200mm and disable SR when you zoom to a lower number, since you might not need SR if you are at 100mm with good light conditions. On my manual lenses I input nearest wider number. In strong light, I might not even use SR (if shutter speed is really fast).

08-23-2017, 07:56 AM	#4
blackest Senior Member Join Date: Jun 2013 Photos: Albums Posts: 171 Original Poster	Originally posted by Na Horuk When you mount a lens that does not communicate focal length, you have to input it by hand. You should input the exact number. Problem is the numbers you can't input and zoom lenses. Yes, SR can make pictures more blurry. I think its only when the focal length that you input is higher than the actual one. Then the SR might overcompensate and introduce blur. If the input number is lower, the SR will simply be less effective, but it won't add blur. With primes, you should input the exact number or the nearest wider number. For zooms people usually input the lowest number they will be using. Some people use 70-200mm zoom only at 200mm, so you can input 200. If you will only use it between 100 and 200, input 100. If you will use it in the whole range, from 70 to 200, then input 70. OR you can input 200mm and disable SR when you zoom to a lower number, since you might not need SR if you are at 100mm with good light conditions. On my manual lenses I input nearest wider number. In strong light, I might not even use SR (if shutter speed is really fast). Thank you both for your rapid replies, so better short rather than long. It's a shame it lives in the menu's, would love it if you could just hit a button and use a command dial. to set focal length I'm starting to add user modes to my camera I mainly use aperture priority with catch in focus on and off I don't know if focal lengths could go in as a user mode. times like this i wish we had a 'magic lantern' for Pentax.

08-23-2017, 08:26 AM	#5
Na Horuk Veteran Member Join Date: Feb 2012 Location: Slovenia, probably Photos: Gallery \| Albums Posts: 11,186	Yea, Pentax firmware was really good, but it could use an update with some more user options Originally posted by blackest so better short rather than long. I think so. Only exception is when you are in macro range. Some user did tests that in macro, with high magnification, you can actually use slightly longer for maximum effect. But in macro range you usually use a tripod anyway (and SR should be disabled when using tripod)

08-23-2017, 08:46 AM	#6
pschlute Moderator Loyal Site Supporter Join Date: Mar 2007 Location: Surrey, UK Photos: Gallery Posts: 8,198	Originally posted by blackest It's a shame it lives in the menu's, would love it if you could just hit a button and use a command dial. to set focal length On the K1 you can. It is in/can be added to the info menu....accessible by pressing INFO

08-23-2017, 10:21 AM	#7
blackest Senior Member Join Date: Jun 2013 Photos: Albums Posts: 171 Original Poster	Originally posted by pschlute On the K1 you can. It is in/can be added to the info menu....accessible by pressing INFO One more reason to get a K1 unfortunately it's not likely in the near future... I was experimenting with the user modes on the k5 and found i couldnt use green button metering on a manual mode or at least i couldn't make it work. user modes do seem to remember focal lengths though which might be handy for ka lenses.

08-23-2017, 10:56 AM	#8
pschlute Moderator Loyal Site Supporter Join Date: Mar 2007 Location: Surrey, UK Photos: Gallery Posts: 8,198	Originally posted by blackest I was experimenting with the user modes on the k5 and found i couldnt use green button metering on a manual mode or at least i couldn't make it work No reason why that should be the case..... unless ..... Did you create the USER mode before you changed the menu setting to "enable aperture ring"? The USER mode may still have that setting off

08-23-2017, 11:10 AM	#9
blackest Senior Member Join Date: Jun 2013 Photos: Albums Posts: 171 Original Poster	Originally posted by pschlute No reason why that should be the case..... unless ..... Did you create the USER mode before you changed the menu setting to "enable aperture ring"? The USER mode may still have that setting off Ok that was weird i now have it working

08-23-2017, 11:59 AM	#10
jup Senior Member Join Date: Nov 2009 Location: San Jose, CA Posts: 103	Originally posted by blackest One more reason to get a K1 unfortunately it's not likely in the near future... KP has the same functionality. You can add focal length setting to INFO menu for quick access. I am pretty sure any K-3ii replacement will have that too.

08-23-2017, 01:13 PM	#11
twilhelm Loyal Site Supporter Join Date: Feb 2009 Location: Florida Photos: Gallery \| Albums Posts: 2,369	On your original post, if you have the IBIS set too long, say shooting with a 28-105, and have it set at 105 but shoot at 28, you will introduce some blur, especially in any low light situation. Don't ask me how I know...

08-23-2017, 01:52 PM	#12
dConvert Junior Member Join Date: Mar 2010 Location: Essex Photos: Gallery Posts: 41	The longer the focal length the more the sensor has to move to correct any movement. If the entered value is less than the actual focal length the movements will be in right direction but not big enough to cancel all shake. So a net improvement is seen. If the focal length entered is slightly too high the sensor will move too much, but may still be an improvement on unstabilsed if the error is not too great. I suspect if the focal length entered is more than twice the real focal length the corrective movement may become greater than the original shake making matters worse. I believe the actual relationship will be down to FOV rather than focal length, but why complicate matters!