Tag Archives: lens

Pentax’ PLM and DC lenses explained

2 Mar

DC (“direct current”) is a kind of focus motor that has been used in Pentax lenses for some time. While it is quiet, it’s not entirely silent. Pentax’ most recent 55-300mm lens features a new type of motor branded as PLM. Here is what Pentax representatives had to say about it in an interview:

The PLM design can quickly activate and allow for faster focusing, but the lens element must be low weight due to limited power (torque).

The DC motor can generate high power (torque) with deceleration mechanisms, which is better for lenses with larger focusing elements. A DC motor can be driven at high speed, but there is an issue that a little sound is generated.

Generally, we use the what we feel is the best focusing mechanism for each specific lens design.

It would be reasonable to suspect that the 55-300mm’s new optical formula and narrower aperture were needed to allow the faster, silent motor to be used, although it should be noted that, like the recent 18-50mm kit and non-kit zoom lenses, the new 55-300mm lens is collapsible to a somewhat smaller size, with the difference between collapsed and uncollapsed size being more pronounced in the 18-50mm.

In the interview, the representatives went on to explain that they do not expect to see PLM in a large aperture lens any time soon, instead putting their money on researching other kinds of motors as well as algorithms to improve autofocus.

Yongnuo 85/1.8 with better bokeh, less CA and noisier AF than Canon

12 Feb

For full details, see the video by Christopher Frost, below:

 

The breakfastographer’s opinion based on the samples shown is that the bokeh is nicer and the CA much lower in the Yongnuo. Corner sharpness is worse, though, and the autofocus has various issues described in the video. No statement was made about focus throw, but it seems to be okay, so manually focusing is an option. At a price of half the Canon, it’s cheaper than a Samyang/Rokinon/Bower/etc., which would also provide only manual focus.

In spite of the corner softness, it’s sold as a full frame lens, and its value proposition as a portrait lens is hard to beat on that format. If you do want to go cheaper, there are 50/1.8 options for APS-C cameras for just over a 100 eurodollars, but bokeh will be better with the 85/full frame combination – or really 85 on any format!

Sigma brings back the moiré

3 Feb

I believe I’ve written on this subject before. DPReview just exclusively announced the results of DxOMark testing of the Sigma 85mm f/1.4 “Art” lens, announcing it to have achieved a perfect 36 “perceptual megapixels” on the Nikon D810’s 36 megapixel sensor. It therefore sort-of-ties with the Sony FE 90mm f/2.8 macro lens, which achieved 42 perceptual megapixels on a 42 megapixel sensor.

Discussion immediately broke out on whether the Zeiss Otus 85/1.4 or Nikon 105/1.4 provided nicer bokeh and whether this was, in fact, more important than sharpness. The Zeiss, in particular, is almost tied with the Sigma for sharpness, and like it excels in many other technically measurable characteristics. The Nikon may be half a step behind, and in fact has a focal length of 94.8mm vs. the Sigma’s 79.9mm, so is more comparable than it sounds at first.

But back to my original point, which is the following:

screen-shot-2017-02-02-at-23-44-40

Excerpt from DPReview sample image no. 30, of the Sigma 85mm samples.

That’s right, moiré. It is a physical certainty that if the sensor has no anti-aliasing filter on it, and the lens outresolves the sensor, you will see moiré on certain subjects (you can find technical details of moiré and aliasing on the Wikipedia pages, moiré pattern and Nyquist frequency). Many manufacturers have dropped the anti-aliasing filter to squeeze more resolution out of their images and as a small cost-saving, or installed a second filter that cancels the first (slight cost increase). Wisely, Canon added the 5Ds without the R to their line-up, which cuts back on moiré much better than the 5Ds R.

In Nikonland, it seems the highest resolving lenses and highest resolving sensors do not make a good pair. That being so, should we buy high resolution cameras at all, and what other choices do we have? Both the Nikon D600 and D610 have weak AA filters (link in Polish) – a bad idea for a lower-resovling camera as the range of lenses that outresolve it will be greater.

Pentax now releases its cameras with an AA filter that works up to shutter speeds of 1/1000s – presumably adequate for most portrait work, and hopeful that anything you’ll want to shoot above that shutter speed will be moving so fast that aliasing is not likely.

In spite of this, Pentax remains, as of this writing, a stalwart of compact lenses that value bokeh over resolution – partly, perhaps, owing to the fact that some of its lenses have been available for quite some time.

It’s well known that Tamron and Pentax have been sitting in a tree lately, and so it is fitting that Tamron somewhat recently launched a line of f/1.8 primes – more compact than the competition’s f/1.4 standard. DxOMark allows comparing Tamron’s 85mm lens with Zeiss’ Otus and Milvus, for instance, and there’s hardly a hair between them. Most surprising perhaps is the performance of the Milvus at less than half the price of the Otus.

Incidentally, while the three aforementioned lenses max out the D800E’s sensor at 36 perceptual megapixels, Sony’s new Gold Master 85mm lens reaches no more than the same value – 36 P-Mpix on an AA-filterless 42 megapixel sensor.

It’s worth asking therefore whether the trend for the second half of this decade is going to continue with lenses increasing in size, resolving power, and price, as exemplified by the Art and Otus, or a reconsideration of traditional values.* If the former, I hope consumers will be asking for strong anti-aliasing filters, and that camera makers, in spite of mobile phone cameras nipping at their heels, will grant that gift.

*An opportunity, perhaps, for Chinese lens makers trying to push into the market.

Update 7 February 2017: For differences between the Art and Otus, check out Roger Cicala’s blog post.

Sigma brings price war to Samyang over 24mm f/1.4

12 Feb

Sigma_24mm_Art

Sigma this week announced its new 24mm lens with f/1.4 as its widest aperture setting. It is part of the Art line, which suggests it will be of a very high optical quality – very sharp, negligible chromatic aberration, possibly low distortion. It was announced to be available in Canon, Nikon and Sigma mounts.

Samyang is the current holder of that spot in the third-party lens landscape, with a manual focus lens that can be found for 514 Euros (it might be cheaper still, I didn’t spend long). Sigma has just confirmed pricing at 849 USD. This is serious pressure on Samyang, as not only does it have less of a reputation with respect to build quality, but its lens also lacks autofocus, which Sigma can offer. The Sigma also looks a little more compact, which is generally desirable, not to mention in a moderate to full wide angle lens (depending on crop factor). On the other hand, the Samyang allows f/22, the Sigma stops at f/16.

It’s clear nonetheless that a few months down the river, with Sigma’s price having dropped to a “street price”, Samyang will have to offer some more serious discounts if it wants to keep selling that lens, since one thing we can be sure of: optically, the Sigma will be competitive.

More details on Pentax’ retractable kit zoom lens

10 Feb

With the release of the Pentax K-S2, Pentax is also releasing a new kit zoom lens, the retractable HD Pentax DA 18-50mm f/4-5.6 DC WR RE. It’s a retractable lens that needs to be manually zoomed forward to its operating distance before you can use it. I suspect in actual operation, this will feel seamless to the user. In exchange, you get the world’s shortest DSLR zoom lens (when it’s stowed away in your bag):

combined

It starts at a sensible f/4, collapses to 1.5 inches (41mm), is weather-sealed, and claimed by Ricoh to be optically superior to its predecessor, the 18-55mm (AL II design) kit zoom. The filter thread is 58mm rather than the 52mm previously used by Pentax. This could be an indication that they are adjusting filter thread sizes on APS-C to be more in line with future full frame lenses. (Previously, 52mm was used on both the 18-55mm and 50-200mm lenses, which were sold together in a dual lens kit with some cameras; the 55-300mm which also exists in a DA-L plastic variant that is exclusive to such bundles (but only available in some localities), always used a 58mm thread.) The front element does not rotate when zooming or focusing. Also, contrary to some rumour, this is not a power zoom lens.

It has a “silent” DC focus motor and HD and SP coatings. Ricoh US customer service told me that the lens must be moved to its extended position manually using the zoom ring, no second motor involved, which presumably helps with both the shortness and longevity of the lens. So everything about this lens is “silent” to the extent that manual operation and DC motors are.

Pentax’ new full-frame lenses

5 Feb

In along with announcing a new full frame camera, Pentax has given details of the two lenses first shown at Photokina that will also support full frame photography.

D-FA* 70-200mm f/2.8

HD Pentax D-FA* 70-200mm f/2.8

The 70-200/2.8 lens is constructed with Aero Bright Coating II in addition to HD coating. According to the press release, this is “a lens-coating nanotechnology that employs a super-low refractive film fabrication process to assure light reflectance lower than that of the conventional Aero Bright Coating”. In addition, it includes a number of sophisticated glass types to minimise aberrations, according to the press release, including “Super ED glass” with properties similar to fluorite.

Wikipedia has this to say about fluorite:

Optical elements made of calcium fluoride, namely of fluorite crystals, are used in some telephoto lenses, to correct color aberration. They are however being replaced with various low dispersion glasses, which have higher refraction index, better dimensional stability, and lower fragility.

Both lenses are weather-sealed to the AW specification (Pentax also maintains the WR label to indicate a lower degree of weather resistance).

Both lenses also have a new kind of focus motor that among other things offers improved quick shift control. Quick shift is Pentax’ name for seamless transitioning from automatic to manual focussing, which is a feature of all ultra/hyper/supersonic drive lenses of any manufacturer (to the best of my knowledge), but in more affordable screwdrive lenses is exclusive to Pentax.

Both of these new lenses are direct current motor driven, and Quick Shift can be set either to ensure autofocus completion, or to allow the user intervention at any point in the autofocus process, leading (if I understand correctly) the autofocus to fade out and relinquish control. Manual focus can also be set as a third alternative – apparently both on the camera body and lens (so MF would have to be disabled both places for any AF to take place).

HD Pentax D-FA 150-450mm f/4.5-5.6

HD Pentax D-FA 150-450mm f/4.5-5.6

Lens prices at launch will be:

  • D-FA* 70-200mm f/2.8 €1999 / $2299.95
  • D-FA 150-450mm f/4.5-5.6 €2199 / $2499.95

hd_lenses_composite2

It’s rumoured that three to four lenses for full frame will be released in 2015 (so perhaps one or two other than the above), then another “six or eight” in 2016.

16mm is the new 18mm

1 Feb

Over the course of 2014, the kit lens landscape has changed significantly, with Samsung announcing not one but two new standard zooms, the 16-50mm f/3.5 to f/5.6 and its weightier sibling, the f/2 to f/2.8 with the same focal length range, both stabilised. Fujifilm also followed up its 16-50mm f/3.5 to f/5.6 from mid-2013 with a new f/2.8 variant at the same focal range just recently. Also during 2014, Tamron announced a 16-300mm superzoom lens for APS-C, at f/3.5 to f/6.3. Pentax has had a 16-50mm standard zoom at f/2.8 for many years, and in 2014 announced a new 16-85mm f/3.5 to f/5.6.

Man and Camel, Morrocco. Taken with Tamron 16-300mm at 16mm. Promotional image by Tamron.

Man and Camel, Morocco. Taken with Tamron 16-300mm at 16mm.

The most active on the 16mm front is probably Sony – they’ve carried a 16-80mm f/3.5 to f/4.5 since 2006, 16-105mm f/3.5 to f/5.6 from 2007 and 16-35mm f/2.8 from 2009 as well as the 2014-introduced 16-35mm f/4 in collaboration with Zeiss – all in A mount. In E mount, there’s the 16-50mm f/3.5 to f/5.6, and again in A mount the much weightier and stabilised 16-50mm f/2.8. But with four major manufacturers fully embracing 16mm as the new wide angle limit standard, 18mm zooms may become a hard sell.

Woman pauses near vendor display. Fes, Morocco. Taken with Tamron 16-300mm at 16mm. Promotional image by Tamron.

Woman pauses near vendor display. Fes, Morocco. Taken with Tamron 16-300mm at 16mm.

Meanwhile, Nikon’s 16-35mm and 16-85mm are a few years old now, and while Canon released a 16-35mm f/4 in 2014 (and has an f/2.8 variant from 2007), it feels like Nikon is not really on top of this story (seemingly betting most of its money on growth in full frame cameras), and Canon does not see going wider as a priority – perhaps sensible given its 7% narrower field of view in the APS-C segment (Canon’s APS-C crop factor, due to a smaller sensor size, is 1.6 vs. most other cameras’ 1.5).

One wonders whether 2013’s star new lens, the Sigma 18-35mm f/1.8, feels a bit left out – undoubtedly a compromise in design the lens to achieve the f/1.8 constant aperture, but a similar compromise will now have to be made by the buyer where wide angle shots are concerned. Ultimately, you’ll never escape the desire, in some situations, to zoom with your feet.