Jump to content

5d mark II strange black dots?


ivan_gunduli_

Recommended Posts

<blockquote>

<p>So, even though the gain may be different (Bernie, it has to be lower to get the same RAW data from a +1EV overexposure, yes?), you'd have more saturated pixels... so I don't particularly see how this should decrease the black dot effect... yet it does.</p>

 

</blockquote>

<p>It was the same raw data with the same Tv and Av. This was to show that iso 50 is really iso 100. I set exposure manually to make sure it was the same in each image. If i had the camera on one of the auto modes, then it would have doubled either Tv or Av when switching to iso 50 from 100. </p>

<p>So, the analogue gain should be the same between 50 and 100. The -1EV correction is performed in the raw converter after the fact.</p>

Link to comment
Share on other sites

  • Replies 187
  • Created
  • Last Reply

Top Posters In This Topic

<p>So then what the hell is the point of ISO 50? Why even put it in there? What a f'in gimmick if that's all it really is. It's like making a 60Hz television capable of accepting 24p HD video... just to take it back to 60Hz via 3:2 pulldown process.</p>

<p>Some of the decisions these companies make just astound me. They just treat the public as if they're unassuming idiots...</p>

<p>Wait a minute...</p>

Link to comment
Share on other sites

<p>I guess the only advantage is that you get less noise in an ISO 50 image vs an ISO 100. The trade-off is 1 stop of dynamic range. It's annoying, like you say, because this is something anyone could do in software themselves, but Canon (to the best of my knowledge) doesn't document this, and many unassuming users might think they are getting something special using ISO 50.</p>
Link to comment
Share on other sites

<p><a href="http://www.canon.com.au/support/customer/default.asp?DXI=KnowledgeBase/Customer/KBArticleForm&File=KB01657&productID=eos5dmkII">Canon announces firmware update <strong><em>in the works</em></strong> for:</a></p>

<blockquote>

<p>“Black dot” phenomenon (the right side of point light sources becomes black) When shooting night scenes, the right side of point light sources (such as lights from building windows) may become black. The phenomenon may become visible if the images are enlarged to 100% or above on a monitor or if large prints of the images are made. <br /> </p>

</blockquote>

<p> Also a banding issue discribed in the above link</p>

Link to comment
Share on other sites

<p>The above post was the Canon announcement from the Australian web site. It is now duplicated on the Canon USA web site. Here's the complete text:</p>

<blockquote>

<p>We have learned that some users of the Canon EOS 5D Mark II digital SLR camera have identified two types of image quality phenomena that appear under certain shooting conditions.</p>

<ol>

<li>“Black dot” phenomenon (the right side of point light sources becomes black) </li>

<li>Vertical banding noise </li>

</ol>

<p> We are currently investigating and analysing the causes, and examining measures to reduce or eliminate these phenomena by providing correction firmware. An announcement will be made on the Canon Web site when such measures have been determined.<br>

<strong>Details of the phenomena and shooting conditions under which they are likely to occur are as follows.</strong></p>

<ol>

<li>“Black dot” phenomenon (the right side of point light sources becomes black)<br />When shooting night scenes, the right side of point light sources (such as lights from building windows) may become black. The phenomenon may become visible if the images are enlarged to 100% or above on a monitor or, if large prints of the images are made. </li>

<li>Vertical banding noise<br />If the recording format is set to sRAW1, vertical banding noise may become visible depending on the camera settings, subject, and background. </li>

</ol>

<ul>

<li>Vertical banding noise is not noticeable if the recording format is set to <strong>sRAW2</strong>. </li>

<li>Vertical banding noise does not occur if the recording format is set to <strong>RAW</strong> or <strong>JPEG</strong>. </li>

<li>Noise can be reduced if C.Fn II-3: Highlight tone priority is set to <strong>0: Disable</strong>. </li>

</ul>

<p> Canon always strives to provide the highest quality products to our customers. We apologize for any inconvenience these phenomena may have caused. We appreciate your kind patronage and support.</p>

</blockquote>

<p>Here is the link for this Canon USA "<strong>Service Notice</strong>" <a href="http://www.usa.canon.com/consumer/controller?act=PgComSmModDisplayAct&fcategoryid=139&modelid=17662&keycode=2112&id=55060">http://www.usa.canon.com/consumer/controller?act=PgComSmModDisplayAct&fcategoryid=139&modelid=17662&keycode=2112&id=55060</a></p>

 

Link to comment
Share on other sites

<p>The above post was the Canon announcement from the Australian web site. It is now duplicated on the Canon USA web site. Here's the complete text:</p>

<blockquote>

<p>We have learned that some users of the Canon EOS 5D Mark II digital SLR camera have identified two types of image quality phenomena that appear under certain shooting conditions.</p>

<ol>

<li>“Black dot” phenomenon (the right side of point light sources becomes black) </li>

<li>Vertical banding noise </li>

</ol>

<p> We are currently investigating and analysing the causes, and examining measures to reduce or eliminate these phenomena by providing correction firmware. An announcement will be made on the Canon Web site when such measures have been determined.<br>

<strong>Details of the phenomena and shooting conditions under which they are likely to occur are as follows.</strong></p>

<ol>

<li>“Black dot” phenomenon (the right side of point light sources becomes black)<br />When shooting night scenes, the right side of point light sources (such as lights from building windows) may become black. The phenomenon may become visible if the images are enlarged to 100% or above on a monitor or, if large prints of the images are made. </li>

<li>Vertical banding noise<br />If the recording format is set to sRAW1, vertical banding noise may become visible depending on the camera settings, subject, and background. </li>

</ol>

<ul>

<li>Vertical banding noise is not noticeable if the recording format is set to <strong>sRAW2</strong>. </li>

<li>Vertical banding noise does not occur if the recording format is set to <strong>RAW</strong> or <strong>JPEG</strong>. </li>

<li>Noise can be reduced if C.Fn II-3: Highlight tone priority is set to <strong>0: Disable</strong>. </li>

</ul>

<p> Canon always strives to provide the highest quality products to our customers. We apologize for any inconvenience these phenomena may have caused. We appreciate your kind patronage and support.</p>

</blockquote>

<p>Here is the link for this Canon USA "<strong>Service Notice</strong>" <a href="http://www.usa.canon.com/consumer/controller?act=PgComSmModDisplayAct&fcategoryid=139&modelid=17662&keycode=2112&id=55060">http://www.usa.canon.com/consumer/controller?act=PgComSmModDisplayAct&fcategoryid=139&modelid=17662&keycode=2112&id=55060</a></p>

 

Link to comment
Share on other sites

<blockquote>

<p>ISO 50 is useful if you are shooting with a fast lens and/or slow shutterspeed in daylight.</p>

</blockquote>

<p>No, it's not, if all the camera is doing at ISO 50 is telling the meter to overexpose by 1EV at an actual ISO of 100, only to pull it back in software during the RAW conversion.</p>

<p>You could do this yourself by prolonging the exposure at ISO 100 by 1EV, then doing a -1EV adjustment in the RAW converter.</p>

<p>Unless the camera's doing something else, which, it seems, it is not, according to Bernie's results.</p>

Link to comment
Share on other sites

<p>Yes, happens in video, as has been shown in Vincent LaForet's (sp?) video in the scene with the couple underneath the cityscape/bridge; and also, on Canon's own marketing video there's some pretty bad pixelation resulting from the, I believe, the black dot problem, right around a candle flame.</p>

<p>Links to both of these examples are posted above, somewhere.</p>

Link to comment
Share on other sites

  • 2 weeks later...

<p>Canon has responded to this, the response has been published on dpreview.com<br>

<a href="http://www.dpreview.com/news/0812/08121902canon5ddots.asp">http://www.dpreview.com/news/0812/08121902canon5ddots.asp</a><br>

<strong></strong><br>

<strong>"Canon responds to black dot and banding concerns</strong><br>

<br /><strong>Thank you for using Canon products. </strong><br>

<strong>We have learned that some users of the Canon EOS 5D Mark II digital SLR camera have identified two types of image quality phenomena that appear under certain shooting conditions. </strong><br>

<strong>“Black dot” phenomenon (the right side of point light sources becomes black) <br />Vertical banding noise <br />We are currently investigating and analysing the causes, and examining measures to reduce or eliminate these phenomena by providing correction firmware. An announcement will be made on </strong><a href="http://www.canon-europe.com"><strong>www.canon-europe.com</strong></a><strong> as soon as measures have been determined.</strong><br>

<strong>Details of the phenomena and shooting conditions under which they are likely to occur are as follows. </strong><br>

<strong>1. “Black dot” phenomenon (the right side of point light sources becomes black)<br />When shooting night scenes, the right side of point light sources (such as lights from building windows) may become black. The phenomenon may become visible if the images are enlarged to 100% or above on a monitor or if extremely large prints of the images are made. </strong><br>

<strong>2. Vertical banding noise<br />If the recording format is set to sRAW1, vertical banding noise may become visible depending on the camera settings, subject, and background.<br />▪ Vertical banding noise is not noticeable if the recording format is set to sRAW2.<br />▪ Vertical banding noise does not occur if the recording format is set to RAW or JPEG. <br />▪ Noise can be reduced if C.Fn II-3: Highlight tone priority is set to 0: Disable.</strong><br>

<strong>Canon apologizes for any inconvenience caused and thanks photographers for their patience. "</strong><br>

<br />now after officially canon admit the problem I'm confused now whether to get the 5D mark II or just buy the old 5D ? any advice pls..</p>

Link to comment
Share on other sites

<p>Just buy and enjoy the pictures.<br />If Canon responded like that, it is the firmware problem, not the sensor.<br />Buy the camera and update the firmware when it becomes available.<br />Black dots don't show up unless it is blown up to 100% or really large print.<br /><a href="http://www.kenrockwell.com/canon/slrs/5d-mark-ii/black-pixels.htm">http://www.kenrockwell.com/canon/slrs/5d-mark-ii/black-pixels.htm</a><br />Check his opinion about black dots. I agree with him and I really like the image quality of this product.</p>
Link to comment
Share on other sites

<ul>

<li><a href="../photodb/user?user_id=2381463"><strong>Rishi Sanyal</strong></a><strong> </strong><a href="../member-status-icons"><strong><img title="Frequent poster" src="http://static.photo.net/v3graphics/member-status-icons/3rolls.gif" alt="" /></strong></a><strong>, Dec 19, 2008; 03:52 p.m.</strong> </li>

<li><strong></strong>

<ul>

<li><strong>ISO 50 is useful if you are shooting with a fast lens and/or slow shutterspeed in daylight.</strong></li>

</ul>

</li>

<li><strong>No, it's not, if all the camera is doing at ISO 50 is telling the meter to overexpose by 1EV at an actual ISO of 100, only to pull it back in software during the RAW conversion.</strong></li>

<li><strong>You could do this yourself by prolonging the exposure at ISO 100 by 1EV, then doing a -1EV adjustment in the RAW converter.</strong></li>

<li><strong></strong></li>

<li><strong>Unless the camera's doing something else, which, it seems, it is not, according to Bernie's results.</strong></li>

</ul>

<p><strong>Are you kidding me ? Have you ever tried to use F1.2 or F1.4 in broad daylight extremely bright ?</strong><br /><strong>you are mensioning "- 1.0 EV" to make it happened.</strong><br /><strong>But what if the shutter speed already hit the maximum shutter speed with the aperture you desired @ ISO 100 ? </strong><strong>And it is still over exposed ?</strong><br /><strong>All you can do is make the aperture smaller than you desired. </strong><strong>(meaning that you have to use F2.0 instead of F1.4 to have "-1 EV" but the effect you you want to have is @ F1.4 ... it is going to make a huge difference.)</strong><br>

<strong>But all you need is just 1/3 ~ 1 stop below to have the apreture you desired and you do not have your ND Filter with you ?</strong><br /><strong>ISO 50 becomes really handy with this kind of situation.</strong></p>

Link to comment
Share on other sites

<p>Brandon-<br /> <br /> a) That's a pretty fast shutter speed. I mean, even at 1.4, 1/8000 should be enough... or at least if it isn't, maybe f2.0 isn't such a terrible aperture? But I digress.<br /> <br /> b) I believe that the point was that "ISO 50" is _actually_ just shooting ISO 100, then taking the raw file and pulling it down one stop. It isn't actually a different ISO. So you can use it, but it isn't really any different from shooting it overexposed at ISO 100 and pulling it back in RAW. No increase in quality, but actually the opposite. <br /> <br /> Or, that's what I interpret the previous message to mean. <br /> <br /> All that being said, I really enjoy my 5d2. I haven't run into the dots, and since it's a loss of quality instead of an increase, I simply don't use ISO 50.</p><div>00RzY5-103115584.jpg.ee258658cd4599d67e0e7728b36fb771.jpg</div>
Link to comment
Share on other sites

<p>Whoa, some people are going formatting-trigger happy.</p>

<p>Thanks Brad for explaining to Brandon my point so I don't have to spend my time doing so :)</p>

<p>Nice shot -- I agree, high ISO will allow for amazing shooting scenarios. Shooting at f/5.0 indoors at night! Ha! Never woulda thought of doing that with, say, film...</p>

<p>That being said, my eye-brain/whatever is trained to pick out defects/flaws in photographs/video imagery, so I just don't think I'd be able to deal with the banding & the black dots. So I'm waiting for a firmware fix.</p>

<p>Interestingly enough, I saw some slight, although higher frequency (so perhaps less noticeable to some) horizontal banding (across the long axis of the CCD) on some sample photos of that orange Ferrari (I think?) shot taken by Nikon's new D3x.</p>

<p>So it'd seem there are still some technological limitations. If you read the white papers for some of these products, it really is amazing how much complexity goes into these systems... no wonder they break apart within a matter of years whereas some 1980s SLRs are still functional today...</p>

Link to comment
Share on other sites

<p>I am not saying ISO 50 is good.<br />I said it comes in handy.<br />I tested them and ISO 100's picture quality is better than ISO 50, but it looks pretty smooth.<br />Well I know that you can adjust the bightness of the picture with the picture taken with RAW and adjust it further.<br />But there is a difference between taking pictures as way they are only with the camera setting and adjusting the pictures later on ...<br />This is a digital world, and it may be right to adjust the pictures with photoshops and other graphic utilities...<br />But I hope some people know what I am saying.<br />If not, well... it was just my opinion.<br />Thanks.</p>

<p>Is there any news about when Canon will release the new firmware yet ?</p>

Link to comment
Share on other sites

<blockquote>

<p>But there is a difference between taking pictures as way they are only with the camera setting and adjusting the pictures later on ...</p>

 

</blockquote>

<p>Says who? Do you have any proof/evidence for this? Do you know how the ISO 50 is implemented by Canon? i.e. the specific algorithm? If not, then you're not qualifed to comment on this, & are just spreading misinformation.</p>

<p>The same scene, at the same EV when taking the shot, has blown out highlights at ISO 50 but no blown out highlights at ISO 100 (the test has already been done on the 5D Mark II). Therefore, this indicates to me, along with other evidence (such as that presented by Bernie above) that ISO 50 is just a 'hack'... and you'd get the same results just taking the shot at 1/gazillionth of a second, having some blown out highlights, then applying -2/3 EV in post-processing. B/c ISO 50 is, apparently, also not saving your highlights from blowing out.</p>

<p>So either the camera does the -2/3 EV, or you do.</p>

<p>I'd love to be proven wrong though, that ISO 50 ACTUALLY does something better (for example, apply less gain than ISO 100... but that's likely not the case, since highlights are blown out MORE at ISO 50 than ISO 100)... but I need more evidence than 'it comes in handy'.</p>

<p>Y'know?</p>

<p>Cheers,<br>

Rishi</p>

Link to comment
Share on other sites

<p>Rishi<br>

I think what your saying is the extended ISOs are similar to PUSH and PULL processing of film. <br>

If I have time today, I''ll run some "Ansel Adams" curves of the 5D II sensor. I'm thininking of shooting a plain white paper at a ten stop EV range (Ansel's Zones I-X) at 4 different ISOs (50, 100, 800, 25,600) and maybe 2 or 3 different light intensities (because of the wide ISO ranges) - with two of the ISOs in Canon's "extended range" (50 and 25,600). With that ISO range, I'm not sure I can do this. Probably need a flash set up.<br>

Photoshop's histogram data gives the mean intensity value as well as the data for each color channel RGB and CMYK. I'll take both RAW and JPGs but I think I want RAW here.<br>

Then a plot of the data (X-axis: EV and Y-axis:Photoshop mean intensity) should reveal if anything is different in the extended ISOs (I'm sure it is - otherwise it wouldn't be an option on the camera).<br>

The heel and toe of the plots will reveal if there is any loss of highlights or shadows at the various ISOs</p>

<p> </p>

Link to comment
Share on other sites

<p>Dennis -- yes exactly, but even worse than 'push/pull'.</p>

<p>Digital ISOs themselves, if I understand correctly, are basically the film equivalents of 'push & pull'. There's a 'native ISO' for the sensor... outside of that, increasing the ISO just increases the gain applied by the amplifiers to the photocell voltages. In other words, say the 'native ISO' is ISO 100. When you expose at ISO 400, you decreased the actual exposure of the sensor by 2 stops, so there was 4 times as less light falling on the sensor. So, very simplistically, the amplifiers would apply 4 times as much gain.</p>

<p>ISO 50 is even worse. Because if the native ISO of the sensor is, again, say 100, then you overexpose the sensor by 2/3 of a stop. So maybe now you've blown out more actual photosites than you would've had you exposed at ISO 100. On top of that, you're applying whatever gain you would've applied at ISO 100 (I'm basing this conclusion on Bernie's data that if you set the shutter speed/aperture the same for both an ISO 50 and ISO 100 shot, the RAW data are identical)... so now the voltages going to the ADC are all higher because you overexposed yet applied the same gain. IF any of these voltages exceeds the maximal input that the ADC maps to the highest bit, then you've lost more highlight data.</p>

<p>But that last one is a big 'IF'. In the best design, the ADC wouldn't behave like that and the maximal output of the amplifiers would be lower than the maximal input of the ADC to leave some 'headroom'. That's my guess anyway. An electronics engineer should step in here... I'm actually underqualified (I'm in biology/chem) to comment on this as this what I've gleaned from what I've read and other discussions I've had.</p>

<p>My point being: this all gets complicated when we're sitting here contemplating without knowing the actual electronic design.</p>

<p>Anyway, Dennis, if you do that test, def let us know the results!</p>

<p>Cheers,<br>

Rishi</p>

Link to comment
Share on other sites

<p>I equate film emulsion thickness, rather than development push/pull, to analog gain in the sensor path. The thicker emulsion allows film to form a viable latent image with less light, at the cost of a grainier image, and the image becomes unuseable at lower light levels (blown highlights) than with a thinner emulsion. <br />I equate the 'expanded' digital ISOs ('digital' gain) with pushing or pulling film. They all result in a reduction in potential dynamic range given a constant analog gain or emulsion thickness, and both involve exposing at an ISO for which the sensor+gain or emulsion was not designed for. Optimal dynamic range was always a battle with film, just as it is with digital. With film we exposed for the shadows and developed for the highlights, the opposite of digital.</p>
Link to comment
Share on other sites

<p>Regarding ISO 50: on the regular 5D, ISO 50 has one stop less dynamic range which is why most landscape shooters keep it at 100, even with a tripod. Canon stated that they made ISO 50 something you had to turn on because of that fact, so people couldn't just easily select it. Knowing that fact of the original, there's good reason to believe that this is the same story with the 5D2.<br>

The noise improvement at ISO 50 (if any) doesn't seem to be worth losing dynamic range. In my landscape shots, I always use 100 and forget that 50 exists. The 5D (1 and 2) are so noiseless at 100, it's crazy. I suggest a good B+W ND filter if you need the longer shutter speed. That filter comes in handy even more now with video on the 5D2, if you want a narrower depth of field during daylight video shooting.</p>

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



×
×
  • Create New...