A590IS porting... - page 42 - DryOS Development - CHDK Forum
supplierdeeply
« previous next »
Pages: 1 ... 37 38 39 40 41 [42] 43 44 45 46 47 ... 97   Go Down

A590IS porting...

  • 968 Replies
  • 410270 Views
*

Offline toby

  • *
  • 46
Re: A590IS porting...
« Reply #410 on: 23 / November / 2008, 11:21:31 »
Advertisements
Now i understand, why noone was interrested in having a bigger range of aperture lol.

Can someone tell me, how i can get the lower limit in DOF in a script, and how the Autofocus works in the A590???


Logged
*

Offline NewbieToobie

  • ***
  • 102
Re: A590IS porting...
« Reply #411 on: 23 / November / 2008, 14:36:17 »
There's a very serious and misleading error in the calculator at that cambridgecolor website. The author doesn't know much about optics. The diffraction limit is also determined by the physical diameter of the optics used to create it. It can't be calculated from the f-ratio alone. For example an 8-inch diameter lens at f-5.0 creates a much smaller airy disk than a 2-inch diameter lens at f-5.0. Basic optics. Every telescope maker knows this. This is why they build larger telescopes. The larger the telescope, the smaller the airy disk, the finer the details that can be resolved.

That site should never be referred to as a reference with that glaring error in its information. This is how myths start on the net. Everyone refers others to a site and nobody bothers to check if that information being spit out is accurate. I don't know how web-site authors get away with this for as long as they do, but I guess they do.

In other words, don't base what you want to do on anything that website says. IT'S WRONG INFORMATION.

Even if the author does correctly include the lens diameter in his calculator, he'll still be in error. It is also determined by how perfectly curved the glass is. This is why mirror-grinders for telescopes try to get the parabola of their mirrors accurate to within 1/8th to 1/10th or less 1-wavelength of light. If the surface of the optics aren't ground properly that too destroys the airy-disk diameter. The larger the optics the more difficult it is to polish properly. This is why smaller lenses can out-resolve larger lenses that aren't curved as accurately.

It's much more complex than that simple calculator there will ever be able to deal with.

He'd have to presume that every lens made is created absolutely perfectly, polished to within 1/10000th the width of one wavelength of light if he wanted to add in the correct calculation from diameter too. We all know that no two lenses are created equal.

That page should be torn down and never referred to again.




« Last Edit: 23 / November / 2008, 15:03:06 by NewbieToobie »
Logged
*

Offline fudgey

  • *****
  • 1705
  • a570is
Re: A590IS porting...
« Reply #412 on: 23 / November / 2008, 15:05:12 »
Quote from: acetone on 23 / November / 2008, 10:50:16
Harware ISO Limits:
Lowest ISO: ISO50
Highest ISO: ~1600

I'm having a hard time evaluating the sequences for the maximum ISO value, because after the first photo, the histogram seems to smooth out somewhat, without actually moving to the left or right.  It'd be awesome if someone could check me on that before I post this set of limits on the wiki.

Well, it's very much possible that those are the camera's jpeg output limits, but if you wish to find the upper _hardware_ ISO limit, you'll have to compare RAW images. For comparison, on a570is and its peers everything above ISO 800 is identical in RAW output, and JPEGs at higher ISO settings are processed in firmware (brightening + heavier noise reduction).
Logged
*

Offline acetone

  • *
  • 8
Re: A590IS porting...
« Reply #413 on: 23 / November / 2008, 18:53:09 »
Quote from: toby on 23 / November / 2008, 11:21:31
Now i understand, why noone was interrested in having a bigger range of aperture lol.

Can someone tell me, how i can get the lower limit in DOF in a script, and how the Autofocus works in the A590???
The built-in DoF calculator/display is your friend -- instructions on the wiki.  No clue about getting the value within scripts (you could program in the calculation from scratch, although it might be slow due to uBasic's 10 ms/command limitation).

Quote from: fudget
if you wish to find the upper _hardware_ ISO limit, you'll have to compare RAW images.
Thanks!  I'll try this and report back -- this probably explains the apparent smoothing-out of the JPEG histogram.  Although in all honesty, the noise at ISO1600 is so extreme that higher sensitivities probably won't be worth it, but would be nice to know simply for curiosity's sake.

Quote from: NewbieToobie
There's a very serious and misleading error in the calculator at that cambridgecolor website. The author doesn't know much about optics. The diffraction limit is also determined by the physical diameter of the optics used to create it. It can't be calculated from the f-ratio alone. For example an 8-inch diameter lens at f-5.0 creates a much smaller airy disk than a 2-inch diameter lens at f-5.0. Basic optics. Every telescope maker knows this. This is why they build larger telescopes. The larger the telescope, the smaller the airy disk, the finer the details that can be resolved.
Everything I've seen is based off of the computation that
Code: [Select]
Airy Disk Diameter = 1.22 * wavelength * f-number (i.e. 2.6, 4.0, 8.0, etc)
I know that it can also be expressed in terms of subtended angles and angular resolution, but only ran the first calculation, and it agreed reasonably with Cambridge In Color.  If this is indeed in error, could you please post the correct calculation, or assist me in doing so?  I really don't think I'll get a good result if I grab my Modern Physics textbook and try to derive from first principles.  Thank you in advance!

Quote from: NewbieToobie
Even if the author does correctly include the lens diameter in his calculator, he'll still be in error. It is also determined by how perfectly curved the glass is.
That makes sense... none of the calculations are perfect, so we're making a set of simplifying assumptions (IE approximating the size of the Airy disk, etc).  Can't we use rough approximations to give an upper limit on resolving power based on diffraction?  We won't ever get results that good in real-life, but at least it'll make clear what the physical limitations are.
Logged
*

Offline El Porco

  • *
  • 3
Re: A590IS porting...
« Reply #414 on: 25 / November / 2008, 10:09:36 »
Hi,

Just a quick question: does anyone have problems with battery draining super fast when all the OSD stuff is showing (histogram and battery voltage, for example) compared to switching the LCD display off? My camera might be defective, and I want to find out before the end of a 15 day "regret" period... As it is now, a fresh set of normal AA's lasts only about 40-50 RAW pics....! With LCD on and all the CHDK goodies running.

Greetings
Logged
*

Offline whim

  • ******
  • 2046
  • A495/590/620/630 ixus70/115/220/230/300/870 S95
Re: A590IS porting...
« Reply #415 on: 25 / November / 2008, 10:22:58 »
Read this: FAQ - CHDK Wiki

Also: even good AA batteries will not do as well as NiMH recharchables for camera's.

wim
Logged
*

Offline toby

  • *
  • 46
Re: A590IS porting...
« Reply #416 on: 25 / November / 2008, 11:44:11 »
Logged
*

Offline whim

  • ******
  • 2046
  • A495/590/620/630 ixus70/115/220/230/300/870 S95
Re: A590IS porting...
« Reply #417 on: 25 / November / 2008, 12:03:21 »
i don't think 4-6 hours is that bad considering that '590 only has 2 AA's (IIRC)
(6 hours x 400 mA = 2400 mAh)
Maybe you should calibrate your battery meter:  Set  OSD -> Battery
to show the battery voltage, and set max/min voltage to, let's say 3000 and 1000.
Then load fully charged batteries, note initial voltage and continue playing with your
cam until it shuts down, giving you the minimum voltage. Plug obtained values back
into menu above.

wim
« Last Edit: 25 / November / 2008, 12:30:20 by whim »
Logged
*

Offline fudgey

  • *****
  • 1705
  • a570is
Re: A590IS porting...
« Reply #418 on: 25 / November / 2008, 12:29:54 »
Yes, 4-6 hours of just playing with it is pretty normal. Also note that your NiMH cells may be bad (stores often sell stuff that's already gone bad due to long storage, your 2700 mAh cells could very well be effectively 1800 mAh) or your charger may be bad (there are loads of crappy chargers that fail to charge properly and many chargers lie about their charging speed in their marketing material. And many if not most inexpensive chargers charge AA/AAA cells in pairs with two cells in series connection, causing bad performance with unmatched cells).

Logged
*

Offline fe50

  • ******
  • 3152
  • IXUS50 & 860, SX10 Star WARs-Star RAWs
    • fe50
Re: A590IS porting...
« Reply #419 on: 25 / November / 2008, 12:52:46 »
The average battery life CIPA (Camera & Imaging Products Association) values for the A590 are

- 200 shoots with AA Alkaline Batteries
- 450 shots with AA NiMH Rechargeable Batteries

(imaging resource review A590, Performance: Canon PowerShot A590 IS Digital Camera Performance - Review - The Imaging Resource!)

If you want to test it by your own, you'll find a link to the CIPA standard DC-002 ("Standard Procedure for Measuring Digital Still Battery Consumption") also there...

*Edit: El Porco,
you should switch to the playback mode when "playing" & exploring the cam & CHDK. The power consumption is much lower then; in record mode the sensor is always on, the power consumption is nearly the maximum level all the time...
So only switch to record mode when all your settings are done & you want to shoot !
« Last Edit: 25 / November / 2008, 13:00:39 by fe50 »
Logged
Pages: 1 ... 37 38 39 40 41 [42] 43 44 45 46 47 ... 97   Go Up
« previous next »
 

Related Topics
SimplePortal 2.3.6 © 2008-2014, SimplePortal