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Forum: Pentax SLR Lens Discussion 04-26-2016, 08:27 AM  
Alternate walk around lens for the K50 over the kit lens.
Posted By ScooterMaxi Jim
Replies: 110
Views: 9,114
That isn't really the case, unless you insist on buying only from B&H. In fact, the 16-85 is $497 at B & H, and the 18-135 is around $330 at Newegg and even $279 at Abe's (some won't buy there). Even when the difference was larger due to initial high demand for the 16-85, it was selling like hot cakes. The lenses aren't comparable in the marketplace.
Forum: Pentax SLR Lens Discussion 04-24-2016, 09:57 PM  
Alternate walk around lens for the K50 over the kit lens.
Posted By ScooterMaxi Jim
Replies: 110
Views: 9,114
UncleVanya - you've got the right idea.

Norm, if this was about landscape lenses - we would be talking about higher end prime lenses for the most part. As for regular, general uses where a zoom will be more versatile, then the need to stop down isn't a priority. It happens that my typical shooting situation often is close to f/4. For instance, it is my preferred f-stop for portrait work because faster yields poor focus on important facial features and smaller apertures don't yield enough background blur.

As for that 31mm comparison, I find it quite odd that one lens wide open is not much sharper than the borders (the other not close at all) and the two lenses are not close to consistent as to where the sharpest center area lands. It is very clear, then, that the two samples are not at all close in overall sample quality. That tends to yield the theory you're forwarding questionable, at best.

Sorry, UncleVanya - I just couldn't resist.
Forum: Pentax SLR Lens Discussion 04-24-2016, 06:55 PM  
Alternate walk around lens for the K50 over the kit lens.
Posted By ScooterMaxi Jim
Replies: 110
Views: 9,114
Oh my, I can't begin to respond, Norm. You certainly can make comparisons from 16mp to 24mm by interpolation. Sure, it isn't exact, but it is better than ballpark. Read the conclusion on the 18-135. They were a bit stunned that the lens was reported back as within spec when they requested fixing it. Look at the comparables to even the lowly 18-55 WR which is sharper in the corners on the wide end (but does not render nearly as well, IMHO).

Stopped down the 16-45 and 18-135 lenses are close to similar, but that really is the refuge of the wishful. The 16-45 peaks at f/5.6 because the crop sensor will always show the greatest sharpness on a quality lens at that f-stop. An inferior lens - such as the 18-135 - will peak at f/8 simply because the mix of lower resolution and diffusion hit something of a middling sweet point at that aperture. The test of a slow zoom is how well it does wide open - because that's not only where the lens is weakest, but it's where you generally have no choice in terms challenging lighting. Simple stuff we all know well.

Look at the 40mm lenses tested on the 16mp and 24 mp sensors - and you'll see the adjusted match to the various ranges are very close, easily within expected copy variation. (The optical design of the two lenses are the same, so they are expected to test out similarly). These are the two higher spec 40mm lenses, not the xs (which still does well, but seems to have a bit more CA for some reason).
Forum: Pentax SLR Lens Discussion 04-24-2016, 04:16 PM  
Alternate walk around lens for the K50 over the kit lens.
Posted By ScooterMaxi Jim
Replies: 110
Views: 9,114
Let's look at the actual numbers, so we can put this to rest. Please pay attention to the ranges of resolution assigned to EX, VG, G, F, P for 16mp vs. 24mp (likely amplified due to AA vs. non AA filter factor). Let's stick to wide open. All modern lenses are pretty decent at f/5.6 - if that setting is stopped down by one stop or a bit more.

At 24mm borders and extreme (corner) the 16-85 is 2295 and 2076 (middle of VG 2070-2410 range, and nudging into the VG range). The 18-135 indicates 2054 border (somewhat below VG) and 1928 extreme (very slightly above the middle of the good range). The 16-45 rates 1959 at border ranking it in the upper third of VG in the 10mp 1750-2050 VG range; the review did not include extreme for 24mm. So, in this instance, it is clear that the 16-45 is slightly ahead of the 16-85 at 24mm, and the 18-135 is quite some distance behind.

Now, you'll be curious to know how the lenses compare where extreme is included - which requires us to look at the numbers at the very wide end. The 18-135 should be superb based on its reputation at the short end, and the fact that 18mm is a heck of alot easier than 16mm. The 16-85 is 1981 border, 1951 extreme (upper good range but well short of 2070 VG line). The 18-135 is 1839 and 1316 - lower half of good range, and well into the POOR range at 18mm where the other two lenses have already sharpened up considerably by narrowing FoV. The 16-45 yields 1959 border (upper third of VG) and 1741 extreme - nearly at the 1750 line where G meets VG. The 16-45 is far closer to VG at extreme than the 16-85, but the 18-135 rates "poor" despite getting the narrower FoV benefit.

I admire the 18-135 for its small size, WR, and OK performance in the lower two-thirds of the range using a good copy, but ultimately it is a superzoom and exhibits those characteristics to an extent. I'm not saying the 16-45 is great at the widest setting, but it is slightly sharper than the 16-85, and a lot sharper than the 18-135 based on the actual measurements (as in facts). In my opinion, the 16-45 is sharpest at 20-21mm, but we don't have test information on that. It is my sense that it is somewhat sharper than the DA 21 I have. Of course, they are pretty close, and sample variation will have an impact.

Unless the Photozone copy of the 18-135 was dropped onto concrete from the 2nd floor (they didn't say that), that copy is so poor that you have to wonder how much better the lens can get. I'm yet to see an expert review or images indicating that the lens competes well with the better zooms of shorter range. In that regard, given the 16-85's wide range - I'm impressed.
Forum: Pentax SLR Lens Discussion 04-23-2016, 02:51 PM  
Alternate walk around lens for the K50 over the kit lens.
Posted By ScooterMaxi Jim
Replies: 110
Views: 9,114
Please don't ascribe info from Photozone that simply isn't the case, even if you are confused about the differences in a lens tested with a 10mp sensor as opposed to 16mp. I will amend my original comment about zooms in that the 16-85 is closely comparable to the 16-45 on the wide end even into the corners. I had forgotten that it is capable of holding f/4 at the wider end into the mid-20s; I'm not fond of mid-range zooms lacking constant aperture. These two lenses are very close to the EX range all the way to the borders.

However, the 18-135 is far from that EX range once off the center area - and is half the price of the 16-85 for good reason beyond the coatings difference (which is a pretty marginal difference, frankly). I don't have a pony in that race, but based on the photos I've seen and the various serious reviews - the 16-85 is easily the best midrange zoom Pentax has produced. No matter how good the 18-135 sample, I'm yet to see photos that have the depth, sharpness and pop you see from the better lenses. It is marginally sharper with better bokeh than the kit - but that's about it.
Forum: Pentax SLR Lens Discussion 04-17-2016, 06:40 PM  
Alternate walk around lens for the K50 over the kit lens.
Posted By ScooterMaxi Jim
Replies: 110
Views: 9,114
There isn't a Pentax prime or zoom at 20-21mm f/4 that will touch the sharpness of the 16-45. While the DA 21 is interesting and adequate wide open, the 16-45 simply is sharper (although with more CA and less overall character). Pentax would do very well to improve the build and provide WR, releasing it with a DC motor, HD coatings and simply re-release in the same optical design. Ultimately, the lens is at least as fast as the other midrange variable aperture zooms on the long end - where the lens speed counts. You also get more consistent exposures with a constant aperture lens.
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