Alley in Pisa, Italy

by Lars Kotthoff

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43

There are many characteristics which make better lenses better. The basic goal of a lens is to render an ideal replica of the framed scene, but because of the limitations of the real world, that's physically difficult. Lenses inevitably introduce optical artifacts not present in the scene itself. So, an important aspect is minimization of artifacts. Good ...


42

Moiré is a form of aliasing whereby false patterns can be observed in an image. Imagine a lighthouse which sends a pulse of light every 5 seconds, and a camera (or other observer) which sees the lighthouse for three seconds and is then blocked from seeing it for three seconds: lighthouse: *....*....*....*....*....*....*....*... observer: ...


36

Increase your ISO as far as you can go without losing too much quality (to get a shutter speed as close as possible to the 1/focal length rule). Practice and use a stable shooting position like one of these to help steady the camera: http://blog.muddyboots.org/2009/04/avoiding-blur-due-to-camera-shake.html Slowly and smoothly press the shutter button, don't ...


29

From a purely theoretical point of view: more megapixels good. People often talk about how high megapixel sensors were now outresolving most lenses, thus there was no point going higher unless using the very best glass. This is not always true. System resolution is the product of lens resolution and sensor resolution. Thus if you improve one, your system ...


27

In digital photography, the moiré effect stems from interference between fine detail in the scene, and the grid of sensels in the sensor. You can also get a moiré pattern when scaling a picture down for display -- in this case, the interference happens between the fine detail in the picture, and the grid of pixels in the display. Either way, you can get ...


24

Downscaling a larger image on computer is almost certainly going to produce a better result. This is because resizing an image is very processor intensive, and there is a difference in quality between the various resampling algorithms (e.g. Lanczos vs Bicubic). Getting a 5 MP camera to produce a 2 MP image is going to cause the camera to perform the resizing ...


21

No. If you shoot in RAW, there is nothing lost. In fact, in RAW, the white balance you set in-camera is nothing but advisory information to the post-processing software. A different multiplier is applied differently to the red, green, and blue channels during RAW conversion depending on the setting, and if you're doing that conversion from a RAW file, you ...


21

I think you're going about this the wrong way. If you have 2GB of images at 4-5MB each, that's somewhere between 400 and 500 images. That's way too many. Even your close friends probably don't want to wade through all of that. Instead, go through and pick out the very best 10%. Or 5% or even 1%. Take some care and write a meaningful caption for each one. An ...


20

Clarification: Firstly, you are correct in stating that sharpness is subjective, but the ability of a camera system to resolve small details can be measured, and this measurement is strongly related to the perceived sharpness. As you image black and white lines that get closer together they will eventually merge into a grey blob. By measuring how close ...


20

To an extent, yes. There are several ways in which the camera body can affect sharpness and image quality in general: Autofocus If your camera's autofocus is inaccurate, your subject might just be slightly out of focus, causing a loss of focus. The 550d has a cross-type center AF point which can focus more accurately with lenses faster than f/2.8; as far ...


20

More than testing you should learn about your new lens. Although it is good to get some sanity checking first: Set up a flat target with sharp details that can cover the field-of-view of your lens. Set up your camera on a tripod pointing strait at the target. Repeatedly autofocus on your target and see if you can improve accuracy by manual focusing. If it ...


20

Regarding composition, it's important to judge all the things that are in the frame. Everything in the frame either hurts or adds to the picture. In this sample picture, the flower pot and glass pane give a clear hint that the photo is made on a window sill. While people do like to eat in a table near window, only few would consider window sill as a ...


20

There are so many variables here, it would be impossible to give you a precise answer. It depends entirely what you are wanting to do... The kit lens can, in many cases, give a satisfactory photograph, however there are two main areas in which the kit lens suffers in competition against a pro lens: Aperture. Kit lenses are slow. They are usually about ...


19

Don't forget to exhale just before triggering the shutter. It works for snipers!


19

Composition: the window pane, blue bowl, and cut-off edges of the plate are distracting. I also find the silver plate itself to be a composition problem: all of the highlights and shadows make it a distracting element. It's dark behind the food -- is this a reflection of you? On the right, behind the lemon reflection is something that looks sort of like a ...


19

The type of lighting, the way the subject reflects light, presence of haze, the lens design and coatings and the dyes used in the sensor all have an influence on the vividness of colours in an image. But the major factor, which outweighs all of these by a significant margin, is how the image is processed. Either in camera or on a PC the saturation settings ...


17

The answer you found on Yahoo is mostly wrong. The basic statement (same as dpollitt's answer here) is correct — theoretically, image quality shouldn't degrade but a number of factors might make it worse. And the list of things that might go wrong is sound enough. But the mapping of symptoms to problems is very inaccurate. Point by point: One would be ...


16

I don't know how it works with this lens, but I've seen charts for Pentax's in-body stabilization system where the data shows that contrary to conventional wisdom I.S. gives a (decreasing but still there) benefit up until rather high shutter speeds, at which point it doesn't matter (and doesn't make things worse). If you have the camera on a very steady ...


16

Anytime you add something in the optical path you will lose quality. The quality you will lose depends on the filter quality, filter type and lighting conditions. Most filters are extremely susceptible to flare because they add a flat reflective surface and can take a great image and make it completely unusable. That does not mean you should never use a ...


15

Philip has it spot on there, resampling on a computer will give you more control and access to better resampling algorithms. There's another reason not to select a smaller size on camera and that is if you download your photos and find one that is really good you can keep it in high resolution. If you set your camera to 2 megapixels there's no going back! ...


15

Decentering is when an element (or more than one) doesn't have its optical axis quite perfectly aligned with the others. Decentering is really a matter of degree -- every lens element is decentered to at least some degree. All that's open to question is whether it's severe enough to cause a real problem. Depending a little on what element is off center, the ...


15

I default to the three-star setting (out of four), but I always use RAW + JPEG so I can revisit the choice, because there are situations where yes, it makes a difference. Particularly, when there is strong contrast across color channels, like a tree with red leaves or flowers against a blue sky, JPEG compression artifacts can be surprisingly visible with the ...


15

Bear with me for a second here for some background.... When you downsample a 4000×3000 image to 400×300, you are "discarding" 11.9 million of the 12 million pixels. This clearly reduces "image quality", depending on what exactly you mean by that term. If you go from 1000×750 to 400×300, you're reducing the area by about 6 times. Again, data is discarded, ...


15

These are known as Chromatic Aberrations or Colour Fringing. These predominantly occur around areas with high contrast such as sharp edges in photographs or around the white water bottle and dark background in your case. A wider apeture can affect the lenses sensitivity to aberrations although certain lenses can see this "effect" vary depending on focal ...


14

It's all about the reaction. Nothing else matters.


14

JPEG actually uses two types of compression, a lossly and a lossless one. Lossless compression doesn't cause artifacts, so we can ignore that part. The particular type of lossy compression in JPEG, called a discrete cosine transform for the math knurds, allows a tradeoff between compression ratio and fidelity. Most software sufaces this as a "quality" ...


14

Note the reasons you received are general statements and are probably sent generically for a great number of images with very little in common. That being said a good number of them apply to your image: Why would you frame something like that. Look at the edge of the plate. I assume it was not moving ;) so there is no reason for it to be cut off. That is ...


14

Ironically, I just did the math for this in another thread. Image quality is a convolution of all imaging system factors. The resolution of the lens or the resolution of the sensor are not independent factors...they are factors that convolve to produce the final "system resolution". If we use your two cameras as examples, we can calculate the resolutions of ...



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