Tag Archives: focus

Sony a99 II: No C-AF in manual video?

15 Feb

Here’s the relevant section of Kai Man Wong’s review of the a99 II, discussing its video capabilities, the f/3.5 caveat, and the missing option to have continuous autofocus when video exposure is set manually:

 

I take my hat off to Kai for delivering a more thorough review of this camera, and in a shorter space of time, than other frequented outlets.

Pentax, why’d you let Nikon steal the user interface?

4 Nov

Just to clarify up front, when I say “steal”, I don’t mean “take a protected design”, I mean “grab the category” or “become best at”.

I’m talking about the incredible extent of manual operation and tactile feedback that was previously offered by the K-5 and is now showcased in even more spectacular fashion by the Nikon Df. Pentax, meanwhile, removed those features from the K-3.

Years ago, when I started to get interested in cameras above the point and shoot ranges, one that caught my eye was the Panasonic Lumix DMC-L10 (why they re-use this repetitive naming with each new camera, I’ve no idea). The reason it caught my eye was that it had double-loaded its mode dial in a rather compelling way. The main knob was a classic mode dial with “red Auto”, PASM, direct access to scene modes for landscape, macro, sports, portrait and night portrait modes as well as SCN and Custom positions for further options. Below that was a lever with positions for single and continuous drive, time delay and some other setting I don’t recall (video?).

Pentax similarly appealed to me years later because the K-5 allowed metering mode (full, centre-weighted and spot) and focus mode (full, point select or central point) to be separately and directly controlled. You can run your thumb over the focus lever and immediately know what setting it’s on without taking your eye away from the viewfinder. You don’t miss a second of action that way.

By contrast, the K-3 has no information on the focus points even in the viewfinder. Exposure mode is visible, but I’ve always had trouble reading that info as often the light outside is much brighter than the illumination of those symbols.

In comes the Df and has many of those things easily visible, although not all of them discernible through tactile feedback. I appreciate Pentax’ ingenuity in offering a stills/video switch – much needed, great thinking – but I question their reluctance to ensure that the existing pivot switches could be accommodated, and that a simple one for the AA filter would also be included. The supersized mic jack truly is a gimmick by comparison – much less worthy of inclusion in my view.

Well, that’s my opinion on the user interface. The K-3 may well prove to be vastly technologically superior to the Df at a lower price point and with the limitations of a smaller sensor, but it would be nice to be left with a feeling that Pentax didn’t fire or retire the one guy that understood user interfaces.

By the way, if they can do a silver and black version, or a K-5 II with and without AA filter, why can’t they omit that stupid mode dial lock release lever and instead release one model with the mode dial lock button and one without? (Read the manual or a good review to know what I’m talking about – not the one by CNET because the reviewer for all I can discern didn’t understand how the lever is functions.) That would have left them space for one more functional lever. Just a thought.

The more megapixels, …

6 Oct

…the sharper your lens has to be.

…the more accurate your focus has to be.

…the faster your shutter has to be OR

…the better your image stabilisation has to be (IBIS, OIS or tripod).

…the bigger your hard disk has to be.

…the faster your computer has to be.

Sharpness

21 Feb

Photography at its core revolves around the challenge of obtaining a sharp and colour-accurate image of a scene. Once we’ve achieved sharpness, we can modify the image in any way we like, even removing the sharpness in creative ways. However, we cannot yet easily move in the opposite direction. Therefore we’re obliged to obtain a sharp image as a first step.

What, then, are the factors that determine the sharpness of the image we obtain?

  1. Lens: Lenses differ in “optical quality”, that is to say, how much heterogeneity in surface structure and material composition there is in the glass. Heterogeneous glass will render blurry images, whereas glass that adheres exactly to the intended design will give sharper images. For this reason, many photographers advocate starting with good glass and a cheap camera body, but this again depends on the intended application – for sports and wildlife photography, you will want to have a camera with a high frame rate in order to avoid missing crucial moments in your scene. This may limit your options to mid- to upper-range camera bodies, and take away from your lens budget.
  2. Sensor: The other piece of hardware that matters is the sensor. As part of the sensor assembly, there will usually be an “anti-aliasing filter”, which adds a small amount of blur to the recorded image to avoid the appearance of aliasing and moiré. Recently, camera manufacturers have tended towards giving a weaker AA filter and render a sharper image. It is partly a matter of personal preference whether to use a stronger AA filter, but keep in mind that this, as well as any other filter you use in front or behind your lens, will influence image sharpness.
  3. Focus accuracy: It is obvious that the autofocus accuracy of a camera will determine sharpness (or focus placement, if you will) when using autofocus. When using manual focus on an SLR, much will depend on your skill, but also on having a large and bright viewfinder that allows you to see your scene accurately as it will be rendered on your sensor. On better cameras, the viewfinder will be adjustable to your preferred way of holding the camera up to your eye, or to your level of near- or far-sightedness. The more customisation your camera offers in this regard, and the more accurately you adjust it, the better your focusing ability will be. When using LiveView, you only need to be able to see whether the image on the screen is sharp. Many now recommend using a camera with “focus peaking” to help with this, which highlights any sharply focused edges in your image.
  4. Stabilisation: If you are using longer exposures (weak light or small aperture), and particularly if shooting at greater zoom lengths (telephotography), you’ll have to consider the merits of stabilising your image to avoid blur, either by using a stabilising aid such as a tripod, monopod, gorillapod, beanbag, window mount, etc., and/or by having a camera or lens that support sensor or optical stabilisation, respectively. So-called digital stabilisation is generally less preferred than the other methods, as it typically “slices” the image into sub-images and re-combines them into your final image following alignment. This process is slower both in the taking and processing of the image, and may increase noise in your image. A widely touted rule of thumb says that optical stabilisation should be preferred for larger focal lengths (zoom distances).
  5. Exposure (shutter) time: As mentioned in the previous section, short exposures require less stabilisation. This is because you’re less likely to shake your camera a sufficient amount during short exposures. On some, especially older, camera models the shutter itself will cause the camera to shake, and in some cases the image stabilisation mechanism is in turn shaken in such a way as to add blur rather than subtract it. It’s good to be aware of such settings and either avoid those exposure timings, or disable the image stabilisation. This will vary from camera model to camera model, so you must do some research on how this relates to your particular camera. Notwithstanding these observations, selecting a short exposure is generally advantageous to the quality of your image, with the following caveat.
  6. ISO level: On digital cameras, you can manually select a virtual “film speed”, which corresponds to what in the old days determined how grainy your film was (grainier film catches light more easily on each grain, but with a loss of detail because the “colour dot” (grain) is larger). Higher ISO levels will cause you to lose detail, and will increase noise in your image. You may then want to remove this noise, which, in addition to the loss of detail already inherent in the high ISO level, will cause your image to become even blurrier. Selecting higher ISO levels will allow you to shoot fast action better, but due to the loss of image detail, you should not always shoot at a high ISO setting, or your sensor will perform far below the capability of the sharp lens I hope you bought.
  7. Aperture: This is a slightly advanced topic, but all lenses are sharper at some aperture settings than others. As a general rule of thumb, f/8 will be quite sharp, but the exact sweet spot will vary from lens to lens. The fall-off in sharpness also varies – some lenses can still be very sharp at f/2.8, and most also generate very acceptable images up to f/11. Changing the aperture is, of course, how we control our depth of field, that is, how “deep” into our image we will reach with the sharpness. A small aperture will give greater depth of field, but in order to obtain a nice “bokeh”, i.e. background smoothness, we need to select smaller apertures. Depending on our personal preferences, a truly great lens might be one that allows us to have a part of the image pin-sharp while rendering great bokeh in the background. The shape of highlights on your bokeh, by the way, is determined by the shape of your aperture. Six aperture blades will give you hexagonal highlights. You can make your own.
  8. Adding light sources (flash): Flash may be a very old and time-tested way to improve sharpness in a moving scene, but I mention it last because flash will definitely change the way your scene appears. When using flash, you will always capture an approximation of what you were looking at in real life. Flash can be a creative medium, and especially in a studio setting, where you have more flexibility over the placement of your light sources, these become an irreplaceable part of your toolkit. However, a camera-mounted flash (with the exception of ring flashes in macro photography) will, in most scenes, cause unsightly shadows to appear behind your subject, so camera-mounted flash should be used cautiously and in small doses when possible. You can offset this effect somewhat by “bouncing” your flash off a nearby matte surface with sufficient reflectivity, which will serve to scatter the light from your flash and make shadows less harsh. However, to cut to the short of it, the added light from a flash allows you to lower your exposure times, giving less shake in your image.