Gary’s Parries 15/10/06

October 15, 2006 | Mark Goldstein | Gary's Parries | 20 Comments |

Gary's ParriesThis week’s Gary’s Parries topics are:

1. Getting Close With Add-On Lenses
2. Electronic Shutters In Full Bloom
3. Picassa Ducks Out On DVD Recording

Introducing this week’s Gary’s Parries column. Everything you always wanted to know about digital cameras, but were afraid to ask. No question too difficult, or too easy. As a Senior Principal Software Engineer, and a former Assistant Professor of Computer Information Systems, as well as a recording studio owner/operator, inventor, and now, a digital camera enthusiast, GARY has more digital camera knowledge in his entire brain than most people have in their little finger. In the unlikely event that GARY would not know the answer to your question, he will answer it anyway, true to the spirit of the word “Parries”, a fencing term which, in this context, implies “cleverly evasive answers”. So let your imagination run wild. Email all your nagging digital camera questions to: garysparries@photographyblog.com , and then, En Garde!

You may also attach to your email an ORIGINAL PHOTO of your choosing. A preview of the photo will be displayed with your question, and a full-sized version will be just a click away. No personal information will be published with your question unless you specifically include it in the text or attached photo of your email, which may be further edited for grammar, content, or other reasons.

***
*** QUESTION 1—- GETTING CLOSE WITH ADD-ON LENSES
***

Hi Gary,

Try this question out for size!

I have used add-on wide-angle and 2x telephoto lens converters on my Canon PowerShot A95, without being impressed with the results. Will I ever get good results with these add-on lenses?

Currently I have a Panasonic Lumix DMC-FZ30, which is giving me great results, but lacks wide-angle so I am thinking of getting one for it.

Regards,
Ian Copple

“When you read this and smell the coffee that’s Synaesthesia!”


***
*** ANSWER 1
***

Great tasting question, Ian. :)

As you may or may not be aware, all converter (a.k.a. add-on) lenses will cause some loss of image sharpness and contrast, but depending on the quality of the lens, this is usually minimal. However, without knowing more about the types of converters you are using, as well as about the specific problems you are having using them with your Canon A95, I will have to answer your question in the general case.

There are four types of problems that typically occur with converter lenses:
(1) Images appear soft
(2) Images exhibit barrel distortion
(3) Images exhibit vignetting
(4) Images exhibit unexpected shadow areas

Problem (1) - Image softness can be caused by improper spacing between the camera lens and the converter lens. If you are using only A95 factory accessories, namely, the Canon LA-DC52D converter lens adapter, Canon WC-DC52C 0.7x wide converter lens, and Canon TC-DC52A 1.75x tele-converter lens, improper spacing is unlikely. However, since you are using a 2x tele-converter, which is NOT an A95 factory accessory, image softness is a very likely possibility.

Fortunately, there are custom spacers you can purchase to adapt alternative converter lenses to your A95. To see an example of the effectiveness of such spacers, check out these LensMate A95 webpages for the Raynox 6600 .66x Wide Converter and Canon TC-DC52 2.4x Tele-Converter (made for A70).

Problem (2) - Barrel distortion, where the normally straight lines of an image appear curved, is a result of the curved surfaces of the lens elements causing different parts of the image to be reproduced with slightly different magnifications. Generally, lenses use paired elements with inversely matched curvatures to cancel out the barrel distortion of each, so the use of a single element converter lens can add considerable distortion to an image.

Fortunately, there are numerous computer software applications to correct for this barrel distortion in post-processing. To see an example of the effectiveness of such software, check out this LensMate A95 webpage for the Raynox 720 .72x Wide Converter w/ and w/o Factorsys Debarrelizer.

Problem (3) - Vignetting, where the periphery of an image appears darker than its center, is caused by the barrel of the converter lens partially blocking the incoming light rays emanating from the edges of an image.

Fortunately, there are two ways to minimize such ‘mechanical’ vignetting: (a) zoom the A95 lens to its full telephoto position and leave it there; and (b) stop the A95 lens down as far as possible. Admittedly, neither of these is an ideal solution.

Problem (4) - Shadows appearing at the bottom of an image when using an internal flash are caused by light from the flash being partially blocked by the large size of the converter lens. The larger the converter lens, the worse the problem.

Fortunately, there is one way to remedy this problem (short of using no flash at all), use an external flash. Unfortunately, if the converter lens is also partially blocking the A95’s flash sensor, even an external flash may not work properly. Similarly, a large converter lens could block the camera’s AF assist lamp, in which case its auto-focus may not work properly, as well.

If you are having problems specifically with your 2x tele-converter, my Canon A95 guru, Myron, suggests as a workaround that you closely compare your results with similar shots made without the use of a tele-converter, but with the additional 2x zoom and corresponding crop accomplished in post-processing using, for example, Photoshop. If the post-processed images look better than the images made with the tele-converter, then why bother?

Unfortunately, Myron does not have an equivalent workaround for a wide converter. However, if you are still considering the purchase of a wide converter for your Panasonic Lumix DMC-FZ30, you may want to check out last week’s Gary’s Parries (see comments 9 thru 13), where Nick in Japan explains that he leaves a Canon 0.7x wide converter attached to his FZ30 - ALL THE TIME - with very good results, albeit not without some post-processing.

[Note: Thank you, Nick, for sharing this vacation photo taken with an FZ30 and attached Canon 0.7x wide converter, although I presume this was not a wide-angle shot :). – Ed.]

***
*** QUESTION 2—- ELECTRONIC SHUTTERS IN FULL BLOOM
***

Gary,

I wonder why you need a mechanical shutter for a digital camera?

I can understand why you need different apertures: to get different depths of field, and to adjust the amount of light striking the image sensor. But why can’t the processor just save the present image that is projected on the LCD? Isn’t that what it does in movie mode?

Regards,
Anders Tiberg


***
*** ANSWER 2
***

Excellent question, Anders, and a bit of a paradox. The ‘Parries’ answer would be that you certainly do not ‘need’ a mechanical shutter for a digital camera, as is evidenced by the overwhelming majority of digital cameras that do not have one. But more to the point of your question, why would anyone ‘want’ a mechanical shutter on a digital camera, especially when you consider its disadvantages?

There are numerous disadvantages to mechanical shutters, including: (1) they are slower than electronic shutters, which can limit a camera’s top shutter speed; (2) they are less accurate than electronic shutters; (3) they require more battery power than electronic shutters; (4) they are, unlike electronic shutters, susceptible to wear and mechanical failure; and (5) for digital cameras that use the combination of a mechanical shutter to cover the low shutter speeds, and an electronic shutter to cover the high shutter speeds, they are an added expense, particularly when you consider that an electronic shutter is capable of covering the camera’s entire range of shutter speeds.

Yet, many high-end cameras do have mechanical shutters, so you would think there has to be SOME advantage to them … and you would be right. The main advantage of mechanical shutters is improved image quality. With mechanical shutters, light strikes the CCD only during the time of exposure; however, with electronic shutters, light strikes the CCD continuously (i.e., even before the exposure starts, and then even after the exposure ends). Due to this ‘extended’ exposure time, there are two problematic phenomena that arise with electronic shutters.

One such problematic phenomenon is called ‘bloom’. This is when the pixels of an image’s high-contrast areas become saturated with charge due to their longer exposure to light, which in turn causes them to overflow to adjacent pixels, thereby making the image’s high-contrast areas appear larger than actual size (i.e., bloom). A mechanical shutter completely eliminates this problem by enabling the exposure to start with totally dark pixels, so as not to become so easily saturated.

Another problematic phenomenon of electronic shutters is called ‘smear’. This is caused by light continuing to strike the CCD after an exposure is complete, even while its image data is being transferred from the CCD, which in turn alters (i.e., smears) the image during the transfer process. The longer the transfer, the larger the smear effect. Once again, a mechanical shutter completely eliminates the problem by enabling the transfer to be carried out in total darkness, so as not to alter the image.

The bottom line is this. With today’s circuit technology, it is certainly feasible to produce a standalone, electronically-shuttered CCD that can (1) instantaneously drain all charge from the pixels immediately prior to an exposure (equivalent to the totally dark exposure start of a mechanical shutter), and (2) instantaneously latch all image data immediately after an exposure (equivalent to the totally dark data transfer of a mechanical shutter); however, the additional circuitry required to enable such capabilities would significantly decrease the percentage of photosensitive material at each photosite, and thus lead to smaller and noisier pixels.

Even so, with the current state of CMOS Image Sensor technology, mechanical shutters for digital cameras are just a ‘click’ away from extinction. :)

[Note: Thank you, Anders, for submitting this photo taken with a Canon PowerShot S1 IS, which appropriately has a combination mechanical + electronic shutter. – Ed.]

***
*** QUESTION 3—- PICASSA DUCKS OUT ON DVD RECORDING
***

Without spending $100, how can I record my digital camera videos from Picassa to DVD?

Thank you,
Gordon

[Note: Picassa DVDs are currently incompatible with home DVD players. – Ed.]


***
*** ANSWER 3
***

Gordon, how’s $39.99 sound? You can download the ACDSee 9 Photo Manager to burn your Picassa videos to DVD, and then watch them on your home DVD system.

DISCLAIMER: As you may know, I am a Mac user. So, to play it safe, I would suggest taking advantage of ACDSee’s ‘free trial offer’ before buying this Windows-only software solely on my recommendation. :)

[Note: Another photo from Nick, this one shot with a Canon 20D while playing “Sea Of Heartbreak” from his van to get the duck’s attention (Nick’s Photography Tip #9). – Ed.]

***
[Column photo “The Photographer” by Brenda LaFleur of Brenda LaFleur Photography.]



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#1 nick in japan

Gary.. The wonder of the screw-in converters is that unlike doublers, they do stuff for you with no measurable loss of "F" stop. Originally designed for video cameras, we quickly found out that by adding one to some 35mm camera lenses we could reach out and not have the speed drop noticably... That may be a great question for "Parries"... But why? Seems like glass, in front of a lens, or, as in a 1.4x, 2x or even 3x multiplier, ALL should reduce the light proportionally to their product rating....
Also, your explanation of distorsions is great, I didn't see a reference to "pincushion", so I assume that that distortion is not present in any kind of adapter?
One more comment, I leave the .7 Canon wide adapter on the FZ-30 for one reason, I feel lost without a wide, 28mm, view, unless I am doing telephoto work specifically. Because the flip down screen of the FZ-30 makes that camera so very easy to use for low angle shots, I decided to just leave it on. A quick "unscrew" and I'm back to the 400+mm super tele ability. The wide adapter gives me wide to about 294mm, with IS too, good enough for me on this camera.
I noticed that the camera loses flash ablility (Pop-up) when the wide adapter setting is selected in the menu, gonna have to see if the wide adapter will work WITHOUT that menu selection, and if it does, then flash is back!

11:06 pm - Sunday, October 15, 2006

#2 Gary's Parries

Nick, I saw this excellent comment when you posted it, but had to go
out. In the interim, I was hoping someone might have answered it for
me, but no such luck. I can answer the first part about pincushioning
right now, but the second part, about why one type of converter lens
changes the camera's f-stop while another does not, will require a bit
more of an explanation. First, the pincushioning.

With the 'A95' converter lenses, pincushioning was not a problem, but
it can be with other converter lenses, particularly with tele-converters
whose magnification is greater than 2x.

Check out this example of the Raynox DCR 2020PRO 2.2x converter.

http://www.lensmateonline.com/newsite/A620A610tele.html

I'll get back to you shortly about the f-stop part of your question. :)

9:28 am - Monday, October 16, 2006

#3 nick in japan

Awesome images at that site, thank you for your consideration, get some sleep!!

9:42 am - Monday, October 16, 2006

#4 Gary's Parries

Just a few more minutes ... it's a tough one. :)

10:32 am - Monday, October 16, 2006

#5 Gary's Parries

Nick, it is true that, for the type of wide and tele-converter lenses that
mount between the camera body and lens, the f-stop of the camera's
lens is multiplied by the magnification factor of the converter lens. For
example, when using a 2x tele-converter, your Sigma Big Ma's rating
of F4 - 6.3 at 50 - 500mm, becomes F8 - 12.6 at 100 - 1000mm.

The reason for this f-stop increase has absolutely nothing to do with
a restriction of light entering the camera. In fact, for our calculations,
we have assumed any restriction of light by the converter lens to be
negligible. The reason for the f-stop increase has ONLY to do with the
definition of f-stop, which is focal length divided by aperture diameter.

Since all 2x converters double the focal length, and since they do not
in any way change the diameter of the lens aperture, it is easy to see
that the f-stop, which is focal length divided by aperture diameter, will
also be doubled.

But what about 2x converters that mount at the 'other' end of a lens?
Don't they also double the focal length? So wouldn't they also double
the f-stop? The answer is 'yes' and 'no'.

Yes, a 2x converter that mounts at the non-camera end of a lens will
double its focal length, but no, it will not double its f-stop. The reason
for this gets back to the definition of f-stop, which will now have to be
slightly modified in order to accommodate this phenomenon.

Not too many people know this, but the real definition of f-stop is the
focal length BEHIND THE APERTURE divided by the aperture diameter.
When a 2x converter mounts in front of the aperture, it's not included
in the f-stop calculation. When a 2x converter is mounted behind the
aperture, and is included in the f-stop calculation. Go figure. :)

11:30 am - Monday, October 16, 2006

#6 nick in japan

Thank you for this, you actually explained it so I got it!
The Bigma, and it's older brother, the 170-500, appear to be the epitome of this foward-mounted magnifying lens, because foward of the main lens stack is a lens that appears to be nothing but a tele converter, but its built into the lens, giving the lenses a great X factor!
There are many, many adapters available now, and I suspect that because of your explanation, lottsa folks will be trying them! I have a friend that uses a 3x , front mount tele adapter on his F828!
On a lens that has a very large front element, there is probabable cost/ manufacturing restrictions that would still make a 1.4X, 2x , behind the lens converter, a smart buy, even with the loss of speed and aperture advantages.
Lens development is a big investment in companies, gonna get better and better, I'm sure.
Thanks again Gary, I'll sleep alot better now !

12:49 pm - Monday, October 16, 2006

#7 Gary's Parries

I'm just glad you didn't ask about the effect on DOF. :)

10:41 am - Wednesday, October 18, 2006

#8 nick in japan

I don't want to know, not a factor for my limited brain-power! I usually just crank 'em wide open and hope for the best bokeh!
Used the 170-500 today instead of the Bigma, for the added speed and shorter DOF.

12:31 pm - Wednesday, October 18, 2006

#9 Gary's Parries

Nick, could you resend me photo P1010132? I thought that was such a
great shot of your family kneeling in the field of flowers, and I wanted
to use it in next week's column, but when I took a closer look, the row
of red flowers behind them was so over-saturated that it looked more
like a painted red stripe. I do not know what happened, but if you can
send it to me unprocessed, that would be the best. Maybe I can use it
in the following week's column.

10:59 am - Thursday, October 19, 2006

#10 nick in japan

OK, you may have to sharpen it a tad, you know how the JPEG degrades after opening/closing/e-mailing!
Busy today, gonna include some shots that you may like.

11:20 am - Thursday, October 19, 2006

#11 nick in japan

OOPS! forgot to add that there is sometimes a focus problem associated with the color red, focus point on the red spectrum is way off unless you are using a super lens, achromatic, or possibly some form of crystal. As you know , similar to focus with the IR spectrum, used to have shift marks on lenses, dont see them anymore.....
The red focus problem, and possible DOF affecting the sharpness of the red flowers, is probably why it looks kinda like a red line in the compressed JPEG e-mail shot.

11:26 am - Thursday, October 19, 2006

#12 Gary's Parries

That could be it.

As a general rule of thumb, the less processing the better. That way
I am not doing processing on top of processing.

11:30 am - Thursday, October 19, 2006

#13 nick in japan

They are just pixels!
I haven't interpolated them, so you have latitude to play, I'm sure.
I need to crank up a bit on my duck pictures, I did some off-hand shooting today and the speed should have about twice that it was, ASA 400 may have done it, I'll try again tomorrow, you should be getting them about now, thats if Mark isn't out testing something new!

11:43 am - Thursday, October 19, 2006

#14 Gary's Parries

Nick, I looked at the new P1010132 you sent, and except for a bit of
softness (which you already mentioned) the over-saturation appears
exactly the same. I am assuming this one is totally unprocessed, not
even a brightness/contrast adjustment?

If that is the case, I'll just use it the way it is. I am beginning to grow
fond of that red stripe anyway. :)

1:06 pm - Friday, October 20, 2006

#15 nick in japan

Gary, as rule of thumb, I generally tweak ALL my images, UNLESS it is something REAL special. This image wasn't one of those REAL special images, so that means that I did something too it, maybe just sharpening, or straightening.
I CAN tell you that because of the overall happiness with what the FZ-30 does, I spend alot less time in Photoshop with it's images.
You have to remember that I take alot of images that I quickly convert to e-mail size, if I fall behind I'm in "deep Kimchi", also rendering the original to a state of being ready for printing on Sundays. When I get a picture that "knocks me out", I save the original, sometimes in TIFF, and add a suffix "b" to the tweaked original to remind me that the untouched original is available for use. Each e-mail image gets an "a", or more, to show it's a compressed-email size.
I'm sorry I didn't make this clear before.
Thank you for even looking at my images, I am honored!

11:10 pm - Friday, October 20, 2006

#16 Gary's Parries

Nick, it's me that should be thanking you for sending me your photos,
knowing what a tough critic I am. :)

Any chance that you have not yet deleted the original from the card?
If you have, don't worry about it. As I said, I like it the way it is.

12:45 pm - Saturday, October 21, 2006

#17 nick in japan

P1010132 has no "b" suffix, that means the original is gone. I routinely place all my images in a folder and clear the card for the next day's shooting, while the battery is getting topped off.
If any of the images I sent you today, from last years's trip to Kuju Flower Park, are of interest, those did have a "b" suffix, I can get into the Iomega and find those originals, for sure, I think I even did a DVD back-up too.
It's getting late now, off to bed, leaving about 0730 tomorrow for the flea market in Hikari, you never replied about the John/Yoko album that is probably still there, .. I'll check my mail before I leave in the morning, to see if you have any thoughts about it.
Oyasuminasai!

1:27 pm - Saturday, October 21, 2006

#18 nick in japan

OOPS!.. Yes you are a tough critic, that is OK! It took a while to get a good reading on exactly where you were coming from at times!

1:34 pm - Saturday, October 21, 2006

#19 Gary's Parries

Nick, thanks for offering. Out of principle, I never bought the Milk and
Honey album because it came out after John Lennon's death, and was
compiled from demos he had made.

3:08 pm - Saturday, October 21, 2006

#20 nick in japan

Thank YOU! No problem, good info tho.
There are many things at a flea market here in Japan that may be interesting , or even valuable, to others. Music is a big part of your life and I'm sure you have things that bring back lottsa memories.
Today and next weekend are ,maybe , the biggest times for flea markets, as the Kintai river- side one ( remember the panoramic from the spring), and a very country-side one in Miwa are next weekend.
I am delighted to search for something of interest to you. Gotta run, thanks for the reply!

10:46 pm - Saturday, October 21, 2006