18

Given that you have explicitly disqualified fungus and dust inside the lens, then the answer is no. A lens will not "naturally" lose sharpness with age. Glass is glass. It is a fixed medium, and assuming a 100 year old lens is in good condition without any extraneous wear and tear like fungus, dust, or a strong enough jolt to misalign one of the internal ...


16

You ask whether a lens can lose sharpness over time, but then go on to say: Please note, I am not talking about general wear and tear, or dust inside the lenses, nor am I talking about fungus in the lens. Which are exactly the reasons lenses lose sharpness over time. So the answer is no - once you exclude all the factors which causes lenses to lose ...


7

I think that you are underestimating how bad a bad lens truly is. It is going to be very obvious if you pickup a real dud and it is acting like a $500 vs $1,600 lens. You can and should run though the related question and its recommendations for testing any new lens: How can I test a new lens to make sure it is operating correctly?. You state that you ...


5

One reason "professional grade" is hard to define is because it's going to get manufacturer's in trouble by setting unreasonable expectations. It's easy, for example, to say that a metal bodied lens is more durable than a plastic composite... but that's not strictly true. The metal body will show dings; the plastic composite won't. The metal body will ...


5

There is one factor not yet mentioned by any of the other answers: separation of elements glued together. As a lens ages the glue that holds some elements to each other can degrade, allowing air to infiltrate between the two lens elements. The areas with air will refract light differently and affect the overall sharpness of the lens. In the context of the ...


5

The lenses in mobile phones are typically made from molded plastic elements rather than ground glass elements, and these are in optically inferior to glass in general (higher dispersion, lower refractive indices). However molded elements have a big advantage in that they can be made into absolutely any shape, whereas glass is very difficult to grind into ...


5

Lens makers strive to make lenses that deliver a faithful image. This has never been achieved, because all lenses suffer from aberrations (optical jargon for error). There are 7 major aberrations. To mitigate, lens makers construct a complex array consisting of several individual lens elements crammed into the lens barrel. Some are air-spaced from one-...


4

Mainly because every point on the front surface of the lens has light from every point in the Field Of View striking it, and other than that which is blocked by the aperture diaphragm the lens refracts all of that light to every point on the image sensor. It is the same reason reflecting telescopes (Newtonian, Maksutov, Cassegrain, Schmidt, etc.) don't have ...


4

This is not a practical answer (it is not a practical question), but it is a precise answer. Let's define "not visible". If in an image, I will offer a description of "not visible" that the object is not more than one pixel size in the image, which certainly will not be considered visible (probably 5 or 10 pixels works as well ...), but "it depends", on ...


4

The same 85/1.8 lens is sold under different names, including Neewer, Opteka, Bower, Vivitar, Lightdow, and others. You don't state what camera, mount, or purpose you want these lenses for, so they may or may not meet your needs. I have used the Neewer 85/1.8 variant. It is reasonably sharp, but doesn't feel sharp (acutance) when used wide open. Like most ...


4

The major manufacturers do not mark lenses as "pro" or "non pro" and they probably have a good reason for that. There are very good professionals that use cheaper "amateur grade" equipment because their back can't handle heavy expensive lenses anymore. There are professional photographers for whom top of the line lenses with latest features are not ...


4

The difference is described by the so called crop factor. The Coolpix P7700 has a much smaller sensor compared to the EOS, thus it will photograph only a smaller section at the same lens focal length. In this case the sensor is so much smaller that it actually looks like it has a focal length longer than the longer actual focal length of the EOS. You ...


3

The main difference between a DSLR and a mobile phone camera is not the lens, but the sensor. The sensor in a typical consumer DSLR is around about 24 x 16 mm, but that in a typical smartphone (the iPhone 6) is around 4.8 x 3.6 mm - or in other words, the DSLR sensor is around 22 times larger than that in a smartphone. As Matt has answered, the lenses in a ...


3

Pictures on the Nikon ad show it's a Jintu, or at least a Jintu box. Jintu say that's an 8-blade aperture. Picture shows 6. You could get one actually purporting to be a Jintu for the same price… or you could save your money. A very very similar Neewer on eBay is £80 & may even be the same thing in a different box. These things often are. I'd say you ...


3

Martin uses Mamiya RZ67 medium format camera for his close up portraits. He lights with 2 Kino flo 4Bank lights and a strobe for background. Negatives are drum scanned for digital editing.


3

Spherical Aberration: Rays coming from near the axis of the lens arrive at the focal plane a form a vertex a specific distance downstream. Rays from the margins of the lens form a vertex at a different distance. Coma: Related to Spherical Aberration but differs in that the patch produced at the focus is not a disk, instead its shape resembles a comet. ...


3

The reason a lens would loose sharpness would most likely be because of wear and tear, dust, or fungus. I would think the glass itself is unlikely to warp unless faced with extremes in temperature. I imaging if you kept a brand-new lens in a dust sealed, climate controlled environment, it would stay sharp for quite some time. But most lenses will need ...


3

The word homogeneity itself refers to the uniformity of a substance. A substance that is of uneven thickness, uneven colour or uneven polarising properties will cause a slight measurable difference in the uniformity of the resulting image in different parts of the frame. In particular, the homogeneity test you linked will be sensitive to differences in ...


3

I will just give you a glimpse of what are you asking, so you can do your own math. We need to take in account: The object 1) What is the color. Diferent colours have diferent wavelengths, so this affects on the sensor reception, difraction, atmospheric absortion, etc. 2) The contrast with the background. This is pretty obvious, a white board on a white ...


2

Under bright sunlight conditions, a young person with 20/20 vision can resolve an object that is approximately 3000 diameters distant. A 2 meter square object has a diagonal measure of 2.8 meters. This object if viewed from 2.8 X 3000 = 8,400 meters, will appear to be a point without discernable dimension. The 3000 times its diameter rule of thumb is too ...


2

Short of using professional lab tools you can't really determine if a single lens is performing up to spec or not. If you have real stinker you can usually tell that, but without a calibrated optical bench it is nigh impossible to tell if a lens is slightly better or slightly worse than the manufacturers stated performance. In the real world what usually ...


2

"Am I simply not seeing it with my unexperienced eyes, or is it that the effect of streaks in a filter are not visible at computer screen resolution? I don't see it even when pixel peeping." It's not visible like that in the image. As the filter is completely out of focus, any flaws will affect most of the image, not single pixels. It would mostly be ...


2

More worried by the specs: Mount: for CANON DSLR Mount Compatible Brand: For Nikon Otherwise you find a "Neewer 85mm f/1,8" on Amazon at about the same price that looks a lot like it and could come from the same plant. You can check the comments of Amazon purchasers, they likely apply to the eBay cousin Buying on Amazon could be safer (return policy, ...


2

Most lenses are at least a little softer wide open, and you should expect some variation across the zoom range as well. Try looking through your archive and comparing different shots taken at specific apertures to see how consistent the issue is. Are all the shots at f/4.5 similar in sharpness, or do they vary a lot? How about f/8? If you can keep the focal ...


2

Be aware that there is current controversy about identically-looking inexpensive lenses sold under different brands, rumoured to be from the same OEM. For example, there are some brands offering lenses that look like Laowa products; however Laowa claims that they are NOT Laowa OEM products but blatant counterfeits (Laowa announcement https://twitter.com/...


1

I do not think the Nikon Df can really be compared against Contax G2. One is a digital camera, the other a film one. Apples and oranges... It is true that having to accommodate the moving mirror limits lens design at the wide end, but while this was true when Biogon was first introduced it was largely overcome by current designs. I would be more concerned ...


1

Your quote basically covers it... With a DLSR, you have to be able to fit the viewing mirror (that bounces the image onto the viewfinder screen) between the lens and the sensor (or film, in old film SLRs). That means that the rear lens element is some way away from the sensor/film, which means that the optical design gets complicated for short focal lengths (...


1

What exactly “professional-grade” means in Nikon line of lenses? It means nothing. It means nothing because Nikon doesn't designate certain lenses as "professional grade" and other lenses as "non-professional grade". Anyone outside of Nikon who uses such terms is doing so based on their own arbitrary definition, not on a definition of "professional grade" ...


1

If both the subject and the camera are located on Earth (or any planet), the distance to the horizon is an upper bound. As explained in the link, with the camera at 1.7 meters above the ground and assuming a spherical planet, the curvature of the Earth limits sight to about 2.9 miles not counting any refraction caused by temperature changes in the air column....


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