fujifilm – Is there a problem with the fact that this camera does not have a lens cap?

A lens hood or cover is hardly needed. Minor scratches will not really affect the quality of your image (PetaPixel source).

Which lens cap Is Protect the lens during transport so you can take a picture instantly – no accidental fingerprints or dirt on the way. That being said, the lens appears to be recessed, making the accidental fingerprint infrequent. When it comes to dust, water marks, etc., it's a camera designed for travel – you do not buy it for exceptional image quality and features; you buy it for take away where you would not want to bring a digital SLR.

He will get wet, be in salt water, become dusty and probably fall several times. Clean the lens before taking the picture will become second nature for this kind of camera anyway. So, not having a lens cap is not a real loss.

How can I tell if a lens has focused breathing?

So recently I had a 90mm macro lens, installed a focus bracketing application on my camera and letting it work. Unfortunately, it turned out that this lens was breathing properly, which means that the actual zoom level of each frame is slightly lowered.

How can I know before buying if a goal has focused breathing? (This was a Sony FE 90mm, in case you were curious.)

Is the Canon EF 24-105mm f / 4L IS USM lens perfocal or not?

I have read a review of Canon EF 24-105mm f / 4L IS USM lens. It said:

The focus changes by zooming.

Zoom in before you concentrate.

Surprised by this (I do not remember ever having seen the scale shift in focus as we zoomed in), I took my goal at 24-105 mm and I did not see it. I made a manual focus so that the focus scale is at a distance of 3 meters at the end 24 mm. I then zoomed in up to 105 mm and the focus remained at 3 meters. The zoom does not affect the focus scale at all (however, auto focus may be affected).

So, is the lens perfect or not? If Ken Rockwell is right, it means that the focus scale is accurate only at a certain focal length.

Does the image quality of the lens affect the "focus and recomposition" technique?

Depends at least on the depth of field.

For example, if you have 85 mm f / 1.2 on a full-frame camera and make a portrait of the head and shoulders (distance: 1.65 meters), the depth of field is 12.3 mm in front of the camera. focal plane and 12.5 mm behind the focal plane. .

What are the chances that the camera will move so that the subject is not close enough to the focal plane? I would say rather high, even if I do not have a full frame camera or 85mm f / 1.2 lens.

Use the right tool for the job. Your camera may have several autofocus points, although in some cases the center point is the most accurate.

On the other hand, the head / shoulders portrait of 135 mm f / 2.8 on a Canon 1.6x crop sensor body (distance: 4.26 meters) has a depth of field of 48 mm in front of the plane focal and 49.2 mm in front of his plane. I would say that in this case, the risk that the subject is no longer perfectly clear is less important.

lens – What exactly are tilt-shift lenses and why are they so important?

See wikipedia.

The part "shift" makes that the verticals remain parallel (on the photo of canonical architecture). Of course, you can correct the perspective in Photoshop, but it loses in pixels or definition. If your building is half as narrow at the top, when you correct the perspective, you reduce the bottom (pixels lost) or widen the top (but if you resize it, it will not look so sharp ).

The tilt allows you to have a focus plan that is not parallel to the sensor plane. I do not think that Photoshop has a magic function to create an object really clear and vague on the initial photo.

Optical – What should be the width of the front of the lens, given the focal length and aperture?

Objectives with very narrow viewing angles require frontal elements roughly equivalent to the size of the entrance pupil. A main telephoto lens will have a front element less than 10% larger than the entrance pupil at the maximum aperture of the lens. Indeed, the light rays captured by the lens are almost perpendicular to the imaging plane and the entrance pupil will not be much larger than the diameter of the front element.

But with wider viewing angles and closer subject distances, the entrance pupil may be much larger than the element before:

A single objective single element:

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A goal composed of several elements:

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If the element before a wider-angle lens was large enough for the entrance pupil to be fully visible subjects focused on the optical axis of the lens, the Purpose would have the effect of seriously vignetting the light from off-axis parts of the mount. Thus, wide-angle lenses tend to have much larger front-end elements than the size of the entrance pupil, so that a larger portion of the entrance pupil is visible from the most peripheral parts of the field of vision.

When parts of the field of view of the lens are obstructed by a full view of the entrance pupil, dark corners and unusually fuzzy shape reflections may result. Consider opening goals with even a Ordinary field of view:

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Such an objective would have a bokeh "cat's eye":

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Even when there is no mechanical vignetting caused by the lens barrel, at a wider angle, the entrance pupil appears to be an oblong shape, rather than an eyebrow. a circle.

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Compare these examples, all for full frame cameras:

  • Canon EF 300mm f / 4 has 77mm filter wires. 300mm / 4 is 75mm
  • Canon EF 100 mm f / 2 with 58 mm filter thread. 100mm / 2 is 50mm
  • Canon EF 85mm f / 1.8 has 58mm filter wires. 85 / 1.8 is 47mm
  • Canon EF 50mm f / 1.4 has 58mm filter wires. 50mm / 1.4 is 36mm
  • Canon EF 35mm f / 2 with 67mm filter thread. 35/2 is 17 mm
  • Canon EF 24mm f / 1.4 has 77mm filter wires. 24mm / 1.4 is 17mm

Your 24-240mm f / 3.5-6.3 lens with a front end of nearly 72mm is probably more focused on reducing vignetting to 24mm and f / 3.5 than on the entrance pupil needed for 240mm and f / 6.3.

On a photo taken with a main lens, what is the cause of the "zoomed" appearance of the bokeh?

This is just an enlightened guess that I have never tested or seen specifically tested with lenses that have been heavily corrected to account for the curvature of the field and the astigmatism, which are intimately related.

Most of the highly corrected field-curvature objectives are used for macro work or for two-dimensional flat document / artwork reproduction (or for very good results on flat test diagrams at close distances so that the seller can declare that they possess the clearest possible goal his class. ") In such cases, the aesthetic properties of the background blur are not a primary consideration when the design of the lens.

Lenses with uncorrected or under-corrected field curvature often also show sagittal astigmatism. The two elements combined, especially when they are used on a medium wide lens with a very large aperture resulting in mechanical vignetting, can produce a type of "swirly" bokeh often called "Petzval effect".

Most lenses that give such a "swirly bokeh" involve a form of mechanical vignetting.

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The large opening to the left presents a mechanical vignetting, when all the entrance pupil is not visible due to the fact that the body of the lens blocks a part of it from an area to always finding in the field of vision of the lens. Even without any appreciable amount of field curvature or astigmatism, such a lens will demonstrate a "cat-eye" bokeh.

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Add to the equation an uncorrected field curvature, as well as a scene with many blurry reflections, such as the shining sky behind the foliage, and the "swokely bokeh" effect.

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What is this swirly bokeh technique and how can I achieve it?
What is the cause of this non-uniform bokeh effect?

If, on the contrary, the lens is strongly corrected for the curvature of the field in order to give it a more or less flat focus field┬╣ and that it also has tangential astigmatism, it seems to me that the shape of the bokeh would be stretched in a radial direction from the center of the lens, as shown in the example picture included in the question. By strongly correcting the curvature of the field, the astigmatism can go from sagittal (as when FC is not corrected) to tangential. If the sagittal MTF value is greater than the tangential FTM value, the tangential lines will be more blurred than the sagittal lines and will therefore be spread over a larger area in the direction perpendicular to these tangential lines.

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What most of us regard as a "good" bokeh, in terms of the quality of the fuzzy reflections, results from a lens design that leaves the curvature of the field and / or spherical aberration under-corrected or not. This means that such an objective will not be suitable for other types of photography, such as landscapes or architecture, when we wish a good sharpness up to the edge of the frame.

The classic example is the Canon EF 85 mm f / 1.2 L II. What gives him such a big bokeh, is the uncorrected field curvature that he shows. This makes it a totally inappropriate target for flat reproduction jobs or for flat test cards, as the focus field at the edges and in the corner will be considerable in front of the flat subject when the center of the goal is perfectly developed. above. If you want to take a perfect shot from a flat test pattern, the $ 350 EF 350/350 EF filter will absolutely clean the floor with the EF 85mm f / 1.2L filter at $ 2,000. But when you want this bewitching bokeh on the edges of a portrait, nothing like the 85 / 1.2!

┬╣ Keep in mind that most lenses have some field curvature. The focus field is not a perfectly flat plane, even with a lens theoretically perfectly manufactured. Highly corrected targets depending on the curvature of the field, such as many macro lenses, retain a focus that is more like a lens lasagna noodles than a flat plane. They are not perfectly flat, they are simply flatter than uncorrected or less corrected lenses. To learn more about the intricacies of the field of concentration, I recommend you read Roger Cicala's excellent series on this subject:
Have fun with the concentration field, part 1
Fun with Field of Focus II: Variation from copy to copy and objective test

lens – What is the physics behind optical apodization?

Apodization filters have long existed around photography. They are often called "soft focus" filters. Objectives with such a filter are sometimes referred to as "soft focus" lenses.

Low-quality, non-apodizing soft focus filters are essentially diffusion filters that also reduce contrast and soften the entire image. The high-end soft focus filters, such as the Zeiss Softar line, let light in the center without diffuse and diffuse only light penetrating the edges of the lens.

This is the basic concept of apodization: let all the most collimated light pass through the center of the lens while letting some of the less collimated light from the edge of the lens pass through. Stopping a normal lens would only let the light through the center, but would not let some of the more diffuse light come off the edges of the lens.

Rather than using a light-diffusing material, as some soft-focus filters do, apodizing lenses use either a ring of neutral density material that is denser near the edges than closer to the center where any Light is allowed to pass or they use plates with holes of different sizes and patterns near the edges.

The Rodenstock Imagon was the most classic objective of the first goals of soft focus. It was designed to fit into the lens tray of a large format camera. Introduced in 1930/31, it was in production until the 1990s. It featured a set of different aperture diaphragms, a / k / a apodization filters, including a main aperture in the middle that produced the aperture. relatively clear image. Each "sink filter" also had smaller holes of varying sizes and patterns on the edges of the different diaphragms, able to "adjust" the amount of blur blur merged with the sharp image projected across the central hole of the diaphragm.

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Associated with an uncorrected spherical aberration and a field curvature that made the focus distance on the edges closer to the camera than the focus distance at the center of the optical axis of the camera. objective, this allowed the proportions of "net" compared to being controlled.

Fuji also made such a lens for 135mm (35mm) format cameras a long time ago, although the pattern was set within the lens, rather than the lens. Before a large / medium format lens such as the Rodenstock.

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Other soft focus lenses, such as the discontinued lens Canon EF 135mm f / 2.8 (with Softfocus mechanism), used different mechanisms to do the same thing: combine the light put at the point coming from the center of an objective which exhibited an uncorrected / under-corrected spherical aberration / curvature of the field with a softer light entering through the edges of the lens so as to be controlled more variably than by a traditional lens design with a single aperture in the diaphragm diaphragm.

In addition, it is possible to digitally simulate the appearance by placing layers with different levels of simulated spherical aberration applied to them with varying degrees of transparency / opacity above the developed base image.

lens – What makes a light bokeh calisson? How to develop this aspect of bokeh?

What creates a calisson-like light bokeh like this (made with the signature Arri T / 1.9)? The more the angles are away from the center, the more the angles are present, why?

Arri Signature

Another objective (Zeiss Supreme T / 1.8) gives another form:

Zeiss Supreme

How (where in the lens) to shape this form? Yet, why (how) in the case Zeiss, the bokeh seems more difficult, even if the opening is the same (1.8 ~ 1.9)?

Does an APS-C lens self-label with actual or actual focal length?

I know that the effective focal length of the 50mm FX lens is actually 50 x 1.5 = 75mm because I shoot with an APS-C sensor.

Not exactly. Not "incorrect", but you have to understand what it means. The 75mm will not be a useful number on DX. The 50mm lens is NOT 75mm, and there is no real reality called effective focal length. It is a purely hypothetical concept. No matter what lens (at any zoom) has only one focal length, where it actually focuses the light to infinity.

The 50mm lens is still only 50mm, whether it's a DX or FX sensor. It's 50mm, end point. That's why it is marked 50mm. 50mm is the only focal length it has.

Now, you may want to compare his field of view to another lens on another sensor. And it's true that the small size of the DX sensor reduces its field of view, so that (if with a 50mm lens) its reduced field of view compares to that of a 75mm lens on a film frame 35 mm see (or an FX frame has the same size as a 35 mm film). But if your lens is marked 50mm, there is still a 50mm lens on any sensor.

The effective focal length only concerns this other lens on this other sensor (35mm film), only because this other 75mm lens seems to have the same field of view on a 35mm film (or the same FX format) as the 50mm lens of the DX sensor. The focal length on the DX sensor is 50 mm. Only this other lens measures 75mm and on this other larger sensor, it has the same field of view as the 50mm on DX. We are talking about two different lenses and two different sensors.

The fact is that many people have used 35mm film for years, even decades. They are very used to what a 50 or 75mm lens will see and do on a 35mm film. Their experience just knows.

Today's smaller digital sensors are changing things (smaller field of view of smaller sensors). This smaller sensor requires shorter lenses now, to see the "same width of view" as that of larger 35mm films. So, their experience only knows (still) about their new camera. The goal of this "effective focal length" is to compare, to tell users familiar with 35mm film what a lens will do on their new cropped sensor. If we say that this 50mm lens works on DX, just as we are used to 75mm on 35mm film (in regards to the field of view), so it makes sense to them, they know what to do with it. ;expect. However, if you are not familiar with the use of a 35mm film, the effective focal length of a 35mm film will probably not be helpful.

Effective focal length published with objectives for smaller sensors always compare to a 35mm film size (same as FX size, called Full Frame). However, we can compare the field of view of any two sensor sizes. For example, imagine 1/2 inch and 2 inch sensors (movie maybe). The largest is 4x larger than the smallest, so the framing factor is 4x, and (with the same lens), the larger one will have a field of view 4x wider than the smallest one and will need to. an effective focal 4x longer to see. the same reduced field of view as the smaller one. Different sensors can have different shapes (3: 2, 4: 3, 16: 9), so the crop factor actually compares the diagonal of the images.

For FX and DX, this ratio is 1.5.

A similar report was still true for different film sizes, but it was only up to FX and DX Digital that we were able to use the same lens on different size sensors. This is therefore becoming a topic of discussion today.