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OlyFlyer
19th January 2008, 08:54 PM
Olympus macro bellows and OM 35 mm lens reversed. Magnification is about 16:1

http://i197.photobucket.com/albums/aa60/olyflyer/Macro/Ballpoint%20pen/P1165980_800.jpg

Unfortunately, the original image looks like this, full of dirt specs on the CCD. Not really disturbing in small format, but larger it is terrible.

http://i197.photobucket.com/albums/aa60/olyflyer/Dirty%20CCD/P1165980_marked_1024.jpg

A 100% crop shows just how bad it is.

http://i197.photobucket.com/albums/aa60/olyflyer/Dirty%20CCD/P1165980_marked_crop.jpg.

It is not the lens, definitely the CCD. Regardless of which lens I use, it is the same and the spots are on the same place. The image below is taken with the ED50/f2 macro lens mounted on my bellows. It also clearly shows the specs.

http://i197.photobucket.com/albums/aa60/olyflyer/Dirty%20CCD/P1176063_marked_1024.jpg

A question to all of you with bellows. Could you check your camera the same way? Macro bellows at maximum extension, white (or light) background, aperture at f22. Of course, all the E-3 should be too new to show theses nasty dust/pollen or whatever.

Cheers.

PeterD
19th January 2008, 09:07 PM
Thanks for your posting OlyFlyer

Thats an interesting series of images. How effective is the dust removal system? I would hate to have a camera without it.

I have often wondered what happens to the dust/pollen that is removed from the CCD. It must remain in the body and need for cleaning must therefore become greater over time.

Can you provide any info on this please?

Cheers

PeterD

OlyFlyer
19th January 2008, 09:59 PM
Actually, as I see it, it is only a problem at very high magnification. Up to 1:1 I can not see any specks, so I assume my kind of problem is limited to a very few people, but certainly people with macro bellows should watch out for it.
I really trust the SSWF, and can imagine how it would be if I did not had one.

PeterD
19th January 2008, 10:11 PM
Actually, as I see it, it is only a problem at very high magnification. Up to 1:1 I can not see any specks, so I assume my kind of problem is limited to a very few people, but certainly people with macro bellows should watch out for it.
I really trust the SSWF, and can imagine how it would be if I did not had one.

Thanks for the reply OlyFlyer. I shall breath a sigh of relief. Of course it is more critical at the higher magnifications and perhaps a useful reminder to all who are into Macro.

Kind regards

PeterD

Jim Ford
19th January 2008, 10:34 PM
Unfortunately, the original image looks like this, full of dirt specs on the CCD. Not really disturbing in small format, but larger it is terrible.


It's interesting - and I think significant - that the spots take the form of a dark doughnut shape surrounded by a lighter ring.

I need to think about it more, but I wonder if the shape of the spots is characteristic of pollen grains? IIRC the pollen grains I've seen under a microscope are semi-transparent, in which case they may act like little lenses to produce the effect. Light entering the grain would tend to be refracted to the middle under the grain to produce the light spot, whilst light striking the sides of the grain at a low angle of incidence would be reflected to produce the halo surrounding the grain.

Jim Ford

theMusicMan
19th January 2008, 11:42 PM
Please excuse my ignorance here, but wouldn't these alleges dust specs turn up on any and every image if the images are 100% framed...? If you use a bellows, isn't all that happens is that one gets to see a close-up highly magnified image of the subject matter - that then fits on the same sized sensor as if one had taken an image of a landscape view at 3 miles away?

There are the same number of pixels on the image i.e. approx 3.5k x 2.5k, and as such wouldn't the alleged dirt/pollen specs still show up. The fact that a bellows is used shouldn't make a bit of difference as far as I can tell.

I will of course bow to the better knowledge of experienced photographers, but please do convince me because as of now, I can't see a bellows making any difference. If there's dirt on the sensor, it would show on any image.

PeterD
20th January 2008, 09:35 AM
Please excuse my ignorance here, but wouldn't these alleges dust specs turn up on any and every image if the images are 100% framed...? If you use a bellows, isn't all that happens is that one gets to see a close-up highly magnified image of the subject matter - that then fits on the same sized sensor as if one had taken an image of a landscape view at 3 miles away?

There are the same number of pixels on the image i.e. approx 3.5k x 2.5k, and as such wouldn't the alleged dirt/pollen specs still show up. The fact that a bellows is used shouldn't make a bit of difference as far as I can tell.

I will of course bow to the better knowledge of experienced photographers, but please do convince me because as of now, I can't see a bellows making any difference. If there's dirt on the sensor, it would show on any image.

Thanks John. I was just getting comfortable with the thought that I should not worry. That was until you came up with the above reply:(
I suppose I shall have to go back to my original query of the efficiency of the dust protection system and where does the removed dust go to?

PeterD

R MacE
20th January 2008, 09:45 AM
I will of course bow to the better knowledge of experienced photographers, but please do convince me because as of now, I can't see a bellows making any difference. If there's dirt on the sensor, it would show on any image.

That certainly makes sense.

Richard

theMusicMan
20th January 2008, 09:46 AM
Very sorry Peter...!! :( Maybe Ian or another expert on here might like to comment and add their experience to the pot?

jdal
20th January 2008, 10:25 AM
....
I suppose I shall have to go back to my original query of the efficiency of the dust protection system and where does the removed dust go to?

PeterD
"The SSWF ..blah..... The removed dust is then captured on an adhesive absorber at the bottom of the filter. ...blah... "
From Oly site here (http://www.olympus.co.uk/consumer/dslr_7051.htm#17741)

PeterD
20th January 2008, 10:36 AM
"The SSWF ..blah..... The removed dust is then captured on an adhesive absorber at the bottom of the filter. ...blah... "
From Oly site here (http://www.olympus.co.uk/consumer/dslr_7051.htm#17741)

Thanks for your post John and also for pointing me back to the olympus site. Looking at the origin of this post (From OlyFlyer), It still leaves me the question how efficient is the SSWF. I am assuming that that the balloint images were made using a SSWF fitted camera.

Best regards

PeterD

Invicta
20th January 2008, 10:44 AM
Thanks for your post John and also for pointing me back to the olympus site. Looking at the origin of this post (From OlyFlyer), It still leaves me the question how efficient is the SSWF. I am assuming that that the balloint images were made using a SSWF fitted camera.

Best regards

PeterD

I asked about this at the V&A event and Oly person informed me that the dust absorber at the bottom of the filter is designed for the life of the camera, i.e. it is not like the crumb tray in a toaster :-). The Oly guy also mentioned that if you have your camera serviced then the dust absorber is replaced with a new one.

jdal
20th January 2008, 11:56 AM
... I am assuming that that the balloint images were made using a SSWF fitted camera.
...
Looking at Olyflyers profile it's an E-500. The oly website blurb is a bit vague, but it does admit that liquids can be a problem and "In such instances, wiping the optical element, such as the Low Pass and Infrared filters, in front of the image sensor with cleaning fluid is effective. ...". I think in this example, sticky pollen may be the culprit.

FWIW, I've just take a couple of shots of the ever present gray skies with my E1 at f22 with two different lenses and there are two very indistinct spots. I would never have noticed unless I was looking for them. This is after 18 months. I can only think that these are dust, but nothing like the spots on the OP images.

SSWF obviously isnt 100%, but it's near enough for me.

OlyFlyer
20th January 2008, 01:25 PM
It's interesting - and I think significant - that the spots take the form of a dark doughnut shape surrounded by a lighter ring.

I need to think about it more, but I wonder if the shape of the spots is characteristic of pollen grains? IIRC the pollen grains I've seen under a microscope are semi-transparent, in which case they may act like little lenses to produce the effect. Light entering the grain would tend to be refracted to the middle under the grain to produce the light spot, whilst light striking the sides of the grain at a low angle of incidence would be reflected to produce the halo surrounding the grain.

Jim Ford Jim, it is an interesting observation, but I don't think we will get a definte answer. I think I let experts do the work, and send my camera to Oly. If they are going to analyse the residue or not, I let them to decide.

OlyFlyer
20th January 2008, 01:46 PM
Looking at another image I took yesterday to see how it effects in normal shooting it is very clear that the answer should be none at all or very little. This is a sky image taken yesterday using the ED50/f2 at f/22 to get the maximum effect.

http://i197.photobucket.com/albums/aa60/olyflyer/Dirty%20CCD/P1196183_unmarked.jpg

I dare say that it can hardly be detected, even at 100% crop of the area where it actually exists.

http://i197.photobucket.com/albums/aa60/olyflyer/Dirty%20CCD/P1196183_unmarked_crop.jpg

Can you see anything? Anyway, even if you can, it can hardly be called disturbing. However, by careful pixel peeping, I could identify these spots below.

http://i197.photobucket.com/albums/aa60/olyflyer/Dirty%20CCD/P1196183_marked_800.jpg

I can not imagine that a normal user would bother about this, that's why I asked those who have bellows to take a similar, high magnification image at f/22 to check their cameras.

R MacE
20th January 2008, 01:53 PM
Thanks for your post John and also for pointing me back to the olympus site. Looking at the origin of this post (From OlyFlyer), It still leaves me the question how efficient is the SSWF. I am assuming that that the balloint images were made using a SSWF fitted camera.

Best regards

PeterD

I can only relate my own experience. Prior to getting an E-1 I used a Nikon D70, dust spots were visible in images even when displayed at 800x600 uncropped when the camera was less than 6 months old. I have yet to see dust spots on a shot taken using the E-1.

The actual vibration of SSWF is only one part of the Olympus anti dust system, the distance that the membrane sits from the sensor also plays a part.

Richard

OlyFlyer
20th January 2008, 02:13 PM
Please excuse my ignorance here, but wouldn't these alleges dust specs turn up on any and every image if the images are 100% framed...? If you use a bellows, isn't all that happens is that one gets to see a close-up highly magnified image of the subject matter - that then fits on the same sized sensor as if one had taken an image of a landscape view at 3 miles away?

There are the same number of pixels on the image i.e. approx 3.5k x 2.5k, and as such wouldn't the alleged dirt/pollen specs still show up. The fact that a bellows is used shouldn't make a bit of difference as far as I can tell.

I will of course bow to the better knowledge of experienced photographers, but please do convince me because as of now, I can't see a bellows making any difference. If there's dirt on the sensor, it would show on any image. You are absolutely right that using bellows to get a super macro image, or using a wide angle to get a super wide angle landscape image uses the same number of pixels. The problem is the aperture. You can never set the same aperture with any lens as the effective aperure using the bellows. When using bellows or any other extension, like tele converters or macro converters or simple extension tubes the actual effective aperture is increased, that is one reason why converters cause light loss and demand increase of shutter speed. Using the bellows in my case, the extension was 245mm to get the 16:1 magnification. I had the lens set to f/22 and used a 35 mm lens at infinity. Now, the effective aperture can quite easily be calculated using the formula below.

Ef = Effective f-value (that is what you get after adding extension tubes or bellows)
If = Indicated f-value (that is shown on your lens or display, the one that is set on the lens)
F = Focal length of the lens
Ex = Extension (total length of the extension tube or bellows)


The formula is: Ef = If x (F + Ex)/F

In my example, with a 35 mm lens and a 245mm extension tube you get ~16:1 magnification and if the lens is set to f/22.0 than:

Ef = 22 x (35 + 245) / 35
The result of the above is 176 (!)

As the aperture opening becomes smaller and smaller, more and more details can be seen nearer and nearer the CCD. Using any lens normally, the effective aperture is the same as the selected aprture. I assume if you would be able to select f/176 on any other lens, that you'd see the problem with that lens as well, but as it is, f/22 being the minimum, we can not see it as clearly as with bellows. Also, as the magnification and the extension is more and more reduced, less and less can be seen. The dirt is there on the same CCD, but can not bee seen as clearly, since it is too much out of focus, as you can see in my sky image example, taken just one day apart.

theMusicMan
20th January 2008, 02:20 PM
Woah OlyFlyer - that's some superb explanation, thanks for this. I can say with 100% certainty, that I have absolutely learned something new today - thanks... :)

OlyFlyer
20th January 2008, 02:21 PM
The actual vibration of SSWF is only one part of the Olympus anti dust system, the distance that the membrane sits from the sensor also plays a part.

Richard

Hi Richard,

I was going to say that. That is exactly what the second reason why it is not clearly visible in normal images. The E-system has a very thin transparant membrane in front of the sensor. It is that membrane which gets shake, not the CCD. As there is room between the membrane and the CCD, if the specs get stuck on the membrane, those are a bit out from the CCD creating an OOF effect, which is very good for normal photography. Without the membrane, we'd probably had to clean our CCD much more often.

Now, it can be the case that my SSWF just stopped functioning, I don't know it yet. But, it definitely is a good and efficient thing in my opinion.

OlyFlyer
20th January 2008, 02:22 PM
Woah OlyFlyer - that's some superb explanation, thanks for this. I can say with 100% certainty, that I have absolutely learned something new today - thanks... :)I appreciate you saying that. It really warms my heart. Thanks.

R MacE
20th January 2008, 03:34 PM
Hi Olyflyer, like Musicman I'd also like to say thanks for your explanation of the effect using bellows has on effective aperture. :)

OlyFlyer
20th January 2008, 04:14 PM
Hi Olyflyer, like Musicman I'd also like to say thanks for your explanation of the effect using bellows has on effective aperture. :)Of course, I appreciate you saying that as well, but actually I stole the text. The original source is this one:

http://olyflyer.blogspot.com/2007/06/calculation-of-effective-aperture-in.html ;)

Anyway, I hope if I am wrong, somebody will correct me.

Jim Ford
20th January 2008, 07:47 PM
How about this for an explanation of the visible dust spots?

I've spent an hour with 'Inkscape' to produce what I think may produce the obvious dust spots. I'm not really up to speed with Inkscape, so forgive the rough diagrams.

The top diagram shows the light path through a large aperture, producing a large but diffuse and faint image on the sensor. In most cases I guess the image it produces is too faint to notice, but perhaps if the region is located, the dropper tool in PS may show a slight difference from the surrounding region.

The bottom diagram shows the light path through a small aperture. As can be seen the rays are getting near parallel, such as to produce a smaller but darker and sharper image than above.

http://homepage.ntlworld.com/james.ford60/dust.jpg

Shoot me down if you think different!
;^)

Jim Ford

OlyFlyer
20th January 2008, 09:34 PM
I won't shoot you because what you say is true. This is what is happening, and at that effective aperture of 176, it is not strange at all that it is more disturbing than in normal images. Now that I know where the spots are, I can locate them also in my sky images, but without the super macro, I would not even see them.

Thank you for the drawing.