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How Determine if a New PowerShot has a Non Adjustable Aperture?

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Offline genosmm

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How Determine if a New PowerShot has a Non Adjustable Aperture?
« on: 29 / July / 2014, 16:22:20 »
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Only recently was told that the IXUS 132 has a non adjustable aperture. If I had known this would have not recommended the camera.

If anyone knows a reason for recommending a non adjustable aperture camera please mention.

Before recommending this camera, I read the reviews but do not remember reading this so checked again
http://www.photographyblog.com/reviews/canon_ixus_132_review/
http://www.ephotozine.com/article/canon-ixus-132-review-22154
http://www.digitalversus.com/digital-camera/ixus-132-p15438/test.html
and still did not find any mention.

Did now notice that http://www.which.co.uk/technology/photography/reviews/digital-cameras/canon-ixus-132/specifications/ mentions in the Full Spec Table "No Aperture priority".

Question:  What is the important thing(s) when trying to determine if the PowerShot camera has a "Non Adjustable Aperture". "No Manual Option" or "No Aperture priority"?  Or something else?

Gene
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Offline waterwingz

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Re: How Determine if a New PowerShot has a Non Adjustable Aperture?
« Reply #1 on: 29 / July / 2014, 17:34:28 »
Quote from: genosmm on 29 / July / 2014, 16:22:20
Only recently was told that the IXUS 132 has a non adjustable aperture. If I had known this would have not recommended the camera.

If anyone knows a reason for recommending a non adjustable aperture camera please mention.

Question:  What is the important thing(s) when trying to determine if the PowerShot camera has a "Non Adjustable Aperture". "No Manual Option" or "No Aperture priority"?  Or something else?
Now that's an interesting couple of questions. I suppose the reasons they don't include an adjustable aperture are cost, size, and the huge depth of field you get from those little lens's and sensors anyway.

But why do the manufacturers seem to hide that fact? I suppose a big percentage of their customers don't even know what an aperture is. But when you get to the detailed spec, you would think there would be one line that says :

Aperture : fixed

But there never is.

When checking camera specs, I usually looked for an Av priority mode and if there isn't one I look to see if the aperture range seems to correspond to the reported zoom range.  After that,  knowing if it comes with an aperture is mostly a guess based in part on which model series the camera is part of.

Although I did get into a flame war on dpreview with one of the local "experts" who wrote a review stating that the A1200 had an adjustable aperture and no ND filter.  I never was able convince him that he was wrong about that.
« Last Edit: 29 / July / 2014, 17:37:18 by waterwingz »
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Offline Hardware_Hacker

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Re: How Determine if a New PowerShot has a Non Adjustable Aperture?
« Reply #2 on: 29 / July / 2014, 21:37:36 »
Quote from: genosmm on 29 / July / 2014, 16:22:20
Question:  What is the important thing(s) when trying to determine if the PowerShot camera has a "Non Adjustable Aperture". "No Manual Option" or "No Aperture priority"? 

Or something else? (???)


Question: - Is this evidence of a "Adjustable Aperture" for a Ixus265-100a

[In] Strings Ixus265-100a.txt

~~~~Iris~~~~

[Iris; Evidence]
00024AF4   StartContiAENoMoveIris
00025C50   StartManualExposureNoMoveIris
00025C7C   StartManualExposureNoMoveIrisKeepBv
0005C7BC   ==== Iris FullOpen ====
0006BF7C   IrisController.c
001DF31C   IrisSpecification.c
003A858C   aIrisCoefficientSubjectDistance[%d] = %d,CheckSum = %d.
003A8901   - IRIS_CONDITION : %d
0080B7B5   IRISSHADJDATA
0080BB6A   NDFILTERPARAMETER
0080BB9F   IRISPARAMETER
00812ED1   ShowFocusLensIrisCoefficientCheckSum
00813119   GetFocusLensIrisCoefficient
008131E3   ChangeIrisSpeed
008131F3   MoveIrisWithAvWithoutBacklash
00813211   MoveIrisToTerminatePosition
0081322D   ResetIris
00813237   MoveIrisWithAv
00813246   GetIrisAv
00814BE1   MoveIrisFullClose
008152EC   MoveIrisFullOpen
00815CD7   ReloadIrisAdjustment

~~~~USM~~~~
[Ultra Sonic Motor]

.... see, attached, for more stuff (???)

H-H
« Last Edit: 30 / July / 2014, 02:23:49 by Hardware_Hacker »
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Offline reyalp

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Re: How Determine if a New PowerShot has a Non Adjustable Aperture?
« Reply #3 on: 29 / July / 2014, 21:42:02 »
Quote from: waterwingz on 29 / July / 2014, 17:34:28
When checking camera specs, I usually looked for an Av priority mode and if there isn't one I look to see if the aperture range seems to correspond to the reported zoom range.
I would consider the lack of an Av mode in the Canon specs pretty much definitive.

The presence of an M mode usually means there is an adjustable aperture, but there has been a few exceptions like the sd990 which let you control the ND and Tv in M mode. It didn't have an "Av" mode.

The current pattern seems to be that all the A, IXUS/ELPH D and N are ND only, while the S, SX and G have adjustable apertures.
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Offline reyalp

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Re: How Determine if a New PowerShot has a Non Adjustable Aperture?
« Reply #4 on: 29 / July / 2014, 21:43:15 »
Quote from: Hardware_Hacker on 29 / July / 2014, 21:37:36
Question: - Is this evidence of a "Adjustable Aperture" for a Ixus265-100a
No, iris related strings appear in the firmware even if the camera doesn't have one.
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Offline waterwingz

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Re: How Determine if a New PowerShot has a Non Adjustable Aperture?
« Reply #5 on: 29 / July / 2014, 22:47:26 »
Quote from: reyalp on 29 / July / 2014, 21:42:02
The current pattern seems to be that all the A, IXUS/ELPH D and N are ND only, while the S, SX and G have adjustable apertures.
That little image H-H posted seems to suggest that his IXUS265 has an adjustable aperture.



But the specs on the Canon UK page don't mention anything about that :

http://www.canon.co.uk/For_Home/Product_Finder/Cameras/Digital_Camera/IXUS/ixus_265_hs/

Maximum f/number   f/3.6 – f/7.0

So where did H-H's little image come from ?


« Last Edit: 29 / July / 2014, 22:58:06 by waterwingz »
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Offline Hardware_Hacker

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Re: How Determine if a New PowerShot has a Non Adjustable Aperture?
« Reply #6 on: 30 / July / 2014, 00:17:03 »
Quote from: waterwingz on 29 / July / 2014, 22:47:26
Quote from: reyalp on 29 / July / 2014, 21:42:02
The current pattern seems to be that all the A, IXUS/ELPH D and N are ND only, while the S, SX and G have adjustable apertures.
That little image H-H posted seems to suggest that his IXUS265 has an adjustable aperture.

But the specs on the Canon UK page don't mention anything about that :

Maximum f/number f/3.6 – f/7.0

So where did H-H's little image come from ?

See the attached Canon.pdf file

Edit #1

@  reyalp  (Reply #4) "...No, iris related strings appear in the firmware even if the camera doesn't have one..."

@  H-H I have just discovered that the Ixus 265 is a very close match to the Sx600.
   So I have almost completed a blind port for the Sx600, but by still using the line-by-line porting method

   Perhaps it's the Sx600 that has the all the, "Real", Iris stuff. (???)

H-H
« Last Edit: 30 / July / 2014, 02:25:04 by Hardware_Hacker »
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Offline waterwingz

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Re: How Determine if a New PowerShot has a Non Adjustable Aperture?
« Reply #7 on: 30 / July / 2014, 00:20:28 »
Quote from: Hardware_Hacker on 30 / July / 2014, 00:17:03
See the attached Canon.pdf file
H-H
Thanks.  The Canon specs on their Australian web site use that nomenclature for several of their cameras.   It's my guess the larger numbers  (F10 & F20) are the effective f-stop with the ND filter in place.

That camera almost certainly does not have an adjustable aperture (other than by changing the zoom position).

« Last Edit: 30 / July / 2014, 00:45:30 by waterwingz »
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Offline fabri22

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Re: How Determine if a New PowerShot has a Non Adjustable Aperture?
« Reply #8 on: 30 / July / 2014, 03:13:38 »
[IMHO]
As far i know a variable diaphragm on such small sensor and lenses would cause only diffraction and a greater production cost.
These small lenses are designed to better perform at max aperture.
Few compact cameras have a fixed diaphragm, nothing more than a hole, instead of a ND filter.
Surely that's what they claim to be an "Adjustable Aperture".
I own a p&s with an "Adjustable Aperture", a panasonic lumix, and could say that its resolution at max aperture outperforms others Av settings.
[/IMHO]
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Offline blackhole

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Re: How Determine if a New PowerShot has a Non Adjustable Aperture?
« Reply #9 on: 30 / July / 2014, 11:45:24 »
Quote
As far i know a variable diaphragm on such small sensor and lenses would cause only diffraction and a greater production cost.
These small lenses are designed to better perform at max aperture.
Hmm, that's not true. The best performance will be in the middle range of aperture or perhaps for one stop more. The biggest aperture (smallest f-number) will always give a more diffuse picture than smaller aperture (larger f-number). If you use the 'Diffraction Limited Aperture Estimator' from this link, you will see that the diffraction can occur only at a middle value of aperture or smaller aperture(larger f-number), which the manufacturer offers to use. If you use a larger f-number, diffraction spikes will begin to appear only on point sources of light, the usual scenes will be sharper than at the larger aperture and other forms of diffraction will not be visible. Anyway camera with adjustable iris diaphragm is always better than one that has a fixed aperture and uses only the ND filter.
http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm
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