leif_goodwin8

My D600 sensor has three splotches visible at F32. They are quite large, maybe 3-5mm wide, and round. Now my understanding is that

small apertures produce highly collimated light, which creates well defined edges for dirt on the filter plate. Hence F32 highlights dirt. I

had never wet cleaned the sensor before I saw them. Two wet cleanings have not removed the splotches. Fortunately they do not appear

at F16, which is the aperture I use the most, but I do a lot of macro photography so it can be an issue.

 

So, does anyone know where the contaminant has come from? And what it is? The sensor does get a lot of dust in use, but I do use live

view a lot, especially with a microscope, so dirt ingress is to he expected. I dry cleaned the sensor, shot off 100 shots, and found no

increase in dirt, so I don't think this is the notorious D600 shutter gubbins issue. I can only think the marks were there from new.

<p>I was going to say what Rodeo Joe said. A TC does not suck up light, it simply magnifies the image, so the sensor receives less light. Increase the magnification, and you reduce DOF. Mouse Peterson's explanations are poor.</p>

<p>Rodeo Joe: Thanks. I know the layout of the viewfinder but I had not realised that the upper surface of the fresnel lens is ground glass, and as you it will be a real image. Yes this may be a trivial issue to some, but it is interesting to some people including myself.</p>

<p>Thanks for the answers.<br>

Rodeo Joe: It seems that you have confirmed that what I read is not patently wrong, except that the value could be a bit less than F2 rather than F2.8. And as you suggest the mirror may be slightly undersized, and (as also suggested by Keith B.) the focus screen may play a role.<br>

One further point though is that human eye's iris also acts as a stop, so it is possible that you saw less of a brightness change between F1.4 and F2 compared to between F2 and F2.8 because your iris was acting as a stop at the wider aperture. That is only a guess, which I think is why the only accurate way to know is to take photographs of the viewfinder image. Thanks for the useful feedback. </p>

<p>Hello Frank. That is a good idea. I did think about photographing the viewfinder image with 50mm F2.8 and 50mm F1.4 lenses mounted and looking for a difference. What you suggest is much simpler, and better. Unfortunately I have no lenses faster than F2.8 so I cannot do this test myself.</p>

<p>I recently read that Nikon DSLR viewfinders effectively limit the lens aperture to about F2.8 and my question is why and how.</p>

<p>My guess is that to ensure that the viewfinder eyepiece is compact and affordable, they introduce a field stop that limits the lens aperture to F2.8 and below. The alternative would be to use the full light cone from an F1.4 lens, which would require a complex and large eyepiece design, and an associated increase in bulk and cost of the DSLR. I guess the pentaprism could also play a role in stopping down the lens.</p>

<p>Some years back I had a polycarbonate body camera with a large lens lacking a tripod mount, and had to mount the camera on the tripod. The base of the camera was visibly warping under the weight of the lens. I suspect a D600 is more robust than that camera (which might have been an old F80 i.e. cheap consumer grade), but even if you cannot see warping, there may well be some deformation. You might try mounting the camera on a tripod with the lens, and testing for droop of the end of the lens relative to where it should be. I'm sure there are ways to measure this. I must admit this is one reason why I am considering the D800 rather than the D600, despite the excessive number of pixies on the D800 sensor.</p>

<p><a href="../photodb/user?user_id=3742851">Apurva Madia</a> said: "Will somebody please explain why ordinary Nikon lenses are not good enough for 36 MP sensor when they are good enough for film? After all, as far as I know film has the highest resolution till date!"</p>

<p>Because film does not have the highest resolution to date, though I suppose there might be some very slow fined grained black and white emulsions out there that equal or best a D3x. Basically even a D3x knocks 35mm colour slide film for six.</p>

 

<p>I did my own rather basic comparison of Velvia 100 with a Nikon D200:<br>

http://www.leifgoodwin.co.uk/DigitalVersusFilm/Velvia100-versus-D200.html<br>

As you can see I used a microscope to avoid the criticism that a slide/film scanner degrades the image from slides/film. There are of course many other comparisons online.</p>

<p>And you also have fine grain slow B&W film, and fast film e.g. ISO 1600. So you can compare high ISO performance. Then there is white balance. And cost. And convenience. Etc.</p>

<p>Tom, apologies for misrepresenting your thesis subject/area, my excuse is that there is too much in this thread to easily read through.</p>

<p>Tim, I certainly would not describe myself as a king. A Ph.D is a very narrow area of work, and as mine was in quantum theory applied to solids, I have no special knowledge of optics, beyond undergraduate courses, and general reading.</p>

<p>As an aside, I have learnt that contrast can be very important in practical terms. I once owned a Nikon fieldscope (one of the cheaper ones), and although resolution was good on a sunny day, as the light dropped, and became flatter, so the resolution dropped. This is not so surprising, as the eye finds it harder to distinguish detail in a low contrast scene. A better fieldscope, such as one of the high end Nikon ones, or the Leica I own, performs much better in low light, as it preserves more of the contrast present in the scene. The same effect can be seen when comparing budget binoculars with high end ones.</p>

<p>Kirk Tuck said, in response to Tom Mann: "I'm sure if you took the time to read Erwin's book instead of selfishly demanding an immediate data dump you would find the material you would like. Again, the material is all out there. Now it's your turn to dig for it. You come across like a disgruntled debate student and that's never fun for anyone else."</p>

<p>Kirk Tuck said: "Wow. Someone looked at my gallery of web images and extrapolated my understanding of resolution versus contrast. Then Tom lectures and corrects everyone. And you wonder why people don't stay and submit to the silliness? Read more, type less."</p>

<p>Kirk, the comments by Tom, myself and others on a claim about contrast and resolution that you made in your blog are polite, reasonable and coherent. You respond with obfuscation and childish abuse. You refer to Tom Mann as a 'student', whereas he has the Ph.D. in optics and astronomy, you don't. Although I have a Ph.D. in physics, I am no expert. Perhaps you think that if you make statements in the public domain, you are so important that they are beyond criticism/discussion. Maybe rather than behaving like a petulant child when someone asks a quite reasonable question, you should grow up and address the issue, namely what is the basis for your claim about contrast and resolution. If it is correct, then we have all learnt something. If it is incorrect, perhaps you should have the grace to accept that fact.</p>

<p>If you cannot cope with criticism of writings you put into the public domain, then don't publish them. If you do, then accept that people will pull you up for technical inaccuracies, on the grounds that misleading people is unfair. If you think the criticism is unjustified, then provide evidence for your claims. But having a temper tantrum does noone any favours.</p>

<p><a href="../photodb/user?user_id=1722891">Tim Lookingbill</a> "So the only way to test whether a lens is offering high resolution is to see how well a tiny tree renders a mile away in like say a landscape. Is that the gist of it?"<br>

In photography the usual way to test resolution is to photograph a lens chart at a well defined distance from the camera. I guess you could photograph a tree, although atmospheric issues enter the equation e.g. air turbulence etc, and you'd have to accurately measure the distance to the tree etc. A lens chart is easier! And before someone mentions it, you are really testing the resolution of the lens sensor pair, unless the sensor easily out resolves the lens.</p>

<p>Tom, thank you for the correction. You are of course correct.</p>

<p><a href="../photodb/user?user_id=1722891">Tim Lookingbill</a> said; "I'm not clear what is meant by lens resolution."</p>

<p>In astronomical circles lens resolution is the ability to separate two point sources. As you move the sources closer together, at some point the images will fuse into one, and they will no longer be resolved. The telescope lens would be used with a high power eyepiece, since the lens out-resolves the human eye. Photographic lenses tend to have a lot of off-axis aberrations, so resolution would depend on the distance from the image centre. In the example images of the chick above, the contrast at boundaries (edges) has been enhanced to make the edges stand out, and give the illusion of greater resolution/sharpness.</p>

<p><a href="../photodb/user?user_id=313836">Kirk Tuck</a> , Dec 01, 2011; 08:05 p.m. said: </p>

 

<p>Kirk Tuck is absolutely correct. Thank you. Start here:<br /> <a rel="nofollow" href="http://www.luminous-landscape.com/tutorials/understanding-series/understanding-mtf.shtml" target="_blank">(link)</a><br /> Well, this is interesting: <a rel="nofollow" href="http://www.luminous-landscape.com/tutorials/understanding-series/lens-contrast.shtml" target="_blank">(link)</a><br /> As is this: <a rel="nofollow" href="http://www.imx.nl/photo/optics/optics/page63.html" target="_blank">http://www.imx.nl/photo/optics/optics/page63.html</a><br /> This is pretty good: <a rel="nofollow" href="http://www.imx.nl/photo/optics/optics/page93.html" target="_blank">http://www.imx.nl/photo/optics/optics/page93.html</a><br /> <a rel="nofollow" href="http://imx.nl/photo/zeiss/page116/page116.html" target="_blank">http://imx.nl/photo/zeiss/page116/page116.html</a><br /> or this: https://sites.google.com/site/seevve/historical-perspective-on-minolta-lens-design-philosophy<br /> some good tidbits here: <a rel="nofollow" href="http://photo.imx.nl/optics/optics/page81.html" target="_blank">http://photo.imx.nl/optics/optics/page81.html</a><br /> <a rel="nofollow" href="http://www.dyxum.com/columns/articles/lenses/sal-85f14cz/carl-zeiss-sal-85f14cz_review.asp" target="_blank">(link)</a></p>

 

<p>_____________________________________________________________________</p>

<p>I had a look at those links and the ones on MTF do no more than confirm my own understanding of MTF, and the fact that high resolution corresponds to high contrast at small spatial frequencies. Some of the text linked to is very long, and discusses loads of side issues unconnected to your post. I'm afraid I'm not prepared to spend an hour or more reading through text, on what might be a wild goose chase, and I doubt others are. Could you please quote relevant extracts?</p>

<p><a name="00ZgMw"></a><a href="../photodb/user?user_id=313836">Kirk Tuck</a> , Dec 01, 2011; 09:59 p.m. said "Contrast, according to both Leica and Zeiss, comes at a cost of resolution."</p>

<p>_____________________________________________________________________</p>

<p>Could you please provide links or cite your sources for that statement. Especially since it contradicts several of the articles that you link to.</p>

<p>Contrast and resolution are closely related. High resolution corresponds to high contrast at high spatial frequencies i.e. small scale. In fact online MTF tests measure contrast at a given spatial frequency as a measure of resolution.<br>

A lot of the difference in the contrast at low spatial frequencies is due to the coatings, although stray light can also reduce contrast which will be more noticeable when the lens is wide open.<br>

You compared a modern lens to a rather old one, and I would not be surprised if differences in coating technology were the main explanation for what you see. Both are primes, and will have good optical designs. There will also be differences between manufacturers too.</p>

<p>I am wary of saying that Kirk Tuck is mistaken, but I believe there is no reason why you cannot design a lens with high resolution and high contrast, and a high quality optic will have both. I do recall that with microscope objectives, planar ones (having a flat field) are in general said to have lower resolution than non planar ones, and this I assume is because the designer aims for an overall improved performance at the expense of the centre of the field. Perhaps that is what Kirk Tuck means. Certainly I was surprised at the high contrast of an old x100 non planar microscope objective (nothing special, just an old achromatic Prior) I own compared to a very modern planar x100 objective. But such a small sample does not say much.</p>

<p><a href="../photodb/user?user_id=478782">Dave Lee</a> said: "Well Shun, maybe everything you've ever purchased has been perfect with no flaws, but for many of us this has not in fact been the case."<br>

The article claims that sample variation is small, but does not dismiss the fact that some lenses are defective. I see no reason to doubt the claims. Over the years I have only had one bad lens, a Nikon 12 to 14mm zoom, and it was unusable between 12 and 14mm at any aperture. Sample variation will be due to slight variation in the refractive index of glass, the curvature of lenses, the machining of lens cells and so on, whereas defects are due to gross errors such as inserting a lens element in reverse, or omitting a shim.<br>

Something he does not mention (but he does mention in another article) is that in his exensive experience the big names such as Nikon have much better quality control than companies such as Sigma.</p>

<p><a href="../photodb/user?user_id=2086552">Clive Woolls</a> said: "You might want to take a look at the Tamron SP AF 90mm f/2.8 Di Macro Lens on the used market. Easily as good as the AF-d and superb for non-macro work too "<br>

I agree, and I have owned both lenses. The Tamron is excellent value. The Nikon VR lens would be nice if you want to do hand held shots such as portraits. VR is not so effective for close ups.</p>

<p><a href="../photodb/user?user_id=22127">Mike Dixon</a> said "If sensor size didn't impact image quality, a 12MP point'n'shoot would provide images that looked as good as shots from a Canon 5Dmk1 or a D700."<br /> You are comparing extremes, and the fact that the D700 cost 10 times as much as a 12MP P&S might enter into the equation. There are too many additional variables such as optics.You cannot expect much from a consumer P&S.<br /> <a href="../photodb/user?user_id=19054">Ilkka Nissila</a> said: "First of all, that is an unusual situation where one would have the same pixel counts in every format ..."<br /> I want to eliminate other variables and consider one i.e. sensor size. I cannot see Rorslett's comparison, but the cameras you list are very different, with different lenses, and processing engines. Even lenses from different manufacturers on the same camera can have significantly different tonal rendition. If I recall correctly Michael Reichmann did a comparison including medium format and compact cameras, and the results were surprising.<br /> <a href="../photodb/user?user_id=19054">Ilkka Nissila</a> said: "At higher ISO the difference between 12 MP DX vs. FX cameras becomes more clear."<br /> Of course. :)<br /> <a href="../photodb/user?user_id=19054">Ilkka Nissila</a> said: "There is some very nice lenses available for MFT but again the MTF figures at e.g. photozone.de even with their expensive primes are not really comparable with Nikon DX or FX results"<br /> I am sure you would agree that MTF plots need to be interpreted with care, and not taken at face value. However, there are some nice lenses for MFT. And for many the whole point of MFT is small size, and some wide angle MFT pancake lenses have excellent performance, with nothing comparable from Nikon. Most Nikon small wide angle primes are iffy. My opinion is that MFT beats the Nikon 1 simply because several manufacturers are making lenses and bodies, which gives the user more choice. I am sure others will disagree.</p>

<p> </p>

<p><a href="../photodb/user?user_id=19054">Ilkka Nissila</a> said "But this is exactly what is seen with different digital sensor sizes."<br>

Not so, assuming the same pixel count. Can you really tell apart two identically composed images taken with FX and DX cameras, each with a 12MP sensor, assuming base ISO, a good lens, well stopped down, and ignoring depth of field and perspective issues?</p>

<p><a href="../photodb/user?user_id=127625">Sanford Edelstein</a> said: "No matter how they spin it, size counts. That is why the $100 Yashicamat I bought at a garage sale took far superior photographs to my Leica M6."<br>

Because whilst they both use film with the same grain size, the Yashicamat takes larger format film, so at a given print size the Yashicamat print will have smoother tones, as the grain will be less evident. Digital is not comparable.</p>

<p>"While Nikon witnessed an overwhelming disappointment over the announcement of its new Nikon 1 series."<br>

It is true that the geekerati were unimpressed, but that is irrelevant. In a years time we will know if the product is selling to its intended market. I think the disappointment in online forums arises because Nikon oriented photo nuts are hoping for an answer to micro 4/3, and the Nikon 1 is not that. The intended user probably cares more about making a short video of their kiddies, than whether or not they can select rear curtain sync flash with -2 stops flash compensation, and half a stop under exposure, using the right hand cross type auto focus sensors, and auto-focus tracking.<br>

You have no reason to be disappointed. If you want a small camera with decent IQ, get a micro 4/3 one. They are selling at very good prices, in the UK anyway, no idea about your country.</p>

<p>There are sample images on Imaging Resource, and some even in daylight show obvious halos around some objects including bright lights but also a red helmet:<br>

http://www.imaging-resource.com/PRODS/NIKONJ1/YDSC_0173.HTM<br>

This cannot be the lens, so it must be the sensor and/or processing. The J1 only has an electronic shutter, so this might be an artifact of the shutter. Not good IMO and a deal breaker. Or a reason to buy the V1, but blimey that one is expensive.<br>

Otherwise the IQ is rather impressive, much better than I have seen from example photos taken with a budget micro 4/3 zoom. If the V1 cures the halos, then it will be impressive. But that price tag ...</p>

<p><a href="../photodb/user?user_id=2071900">Dan South</a> <a href="../member-status-icons"><img title="Frequent poster" src="../v3graphics/member-status-icons/3rolls.gif" alt="" /></a>, Sep 15, 2011; 06:27 p.m.</p>

 

<p>Dan South said: "I salute Nikon for telling the camera customer to stick misleading rumors where the sun doesn't shine."<br>

That would be England then ...</p>

<p>People get too wound up over rumours.</p>

 

<p>Thom Hogan is often very critical of Nikon, and seems to think he knows far better how to manage the company, due to his past experience in business. He is always saying that they are doing things wrong. And yet Nikon are doing very well. He is an intelligent man, writes good reviews, but I give his Nikon analysis articles a miss as I find him too opinionated. They are his opinion, no more.</p>