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Forum: Pentax SLR Lens Discussion 10-11-2017, 08:05 AM  
What's the best Pentax prime?
Posted By Ikarus
Replies: 171
Views: 7,648
The original post used "dollars over rating" and sorted low to high. I used "mean-subtracted rating over dollars" and sorted high to low, the benefit being that you avoid division by zero for a lens that hits the mean rating.
Forum: Pentax SLR Lens Discussion 10-11-2017, 12:47 AM  
What's the best Pentax prime?
Posted By Ikarus
Replies: 171
Views: 7,648
Evidently. :) I was trying to prove to you that subtracting the mean rating before computing the ratio results in a more sensible rank ordering of the lenses.
Forum: Pentax SLR Lens Discussion 10-10-2017, 06:30 PM  
What's the best Pentax prime?
Posted By Ikarus
Replies: 171
Views: 7,648
Well, let's just try, shall we? Previous first three:

1 SMC Pentax-M 50mm F2 8.22 24 (91) 2.92
2 SMC Pentax-A 50mm F2 7.84 34 (63) 4.34
3 SMC Pentax-M 50mm F1.7 9.38 41 (207) 4.37

Let's say the average lens rating is 8.22 (I don't actually know, I assume it's probably more around 8.5). After mean subtraction, the ranking according to the "mean-subtracted rating divided by dollars ratio" is:

1 SMC Pentax-M 50mm F1.7 +1.17 41 (207) 0.03
2 SMC Pentax-M 50mm F2 0 24 (91) 0
3 SMC Pentax-A 50mm F2 -0.38 34 (63) -0.01

Considering the other lenses on that list all have a rating above 8.22, the two 50mm F2 would actually end up all the way at the bottom. Makes a whole lot more sense like this.
Forum: Pentax SLR Lens Discussion 10-10-2017, 09:49 AM  
What's the best Pentax prime?
Posted By Ikarus
Replies: 171
Views: 7,648
The ratings scale being heavily biased towards the 10 end of the scale is the key problem here. If you do the same exercise with the mean rating across all lenses subtracted from the actual, you'll get a very different picture. Your current bargain leader will definitely no longer be at the top, as it shouldn't be.
Forum: Pentax DSLR Discussion 10-05-2017, 08:34 AM  
DPReview High ISO Noise D850 vs K-1
Posted By Ikarus
Replies: 29
Views: 1,684
I agree it's nitpicking, but it's fun, isn't it? To my eyes, the best quality output is from the K-1 with pixel shift enabled. In the lithography section, it cleanly resolves all the vertical lines without any moire artifacts whatsoever. It beats the pants off the D850 at half the price. What a camera!
Forum: Pentax DSLR Discussion 10-05-2017, 07:35 AM  
DPReview High ISO Noise D850 vs K-1
Posted By Ikarus
Replies: 29
Views: 1,684
Where did I say I love it? How much clearer could I be by calling it "a moire and CA feast of epic proportions"?

That doesn't take away from the fact that the D850 shows more detail, albeit some of it false. Personally, I'd rather not see one if it comes with the other, since one cannot tell which is which.

Interestingly, the K-1 shows a milder form of the same type of artifact in this section for higher ISO, e.g. 400 and 800.
Forum: Pentax DSLR Discussion 10-04-2017, 06:12 PM  
DPReview High ISO Noise D850 vs K-1
Posted By Ikarus
Replies: 29
Views: 1,684
Which part? The D850 has no AA filter, and it shows in the lithography part of the image. Whether or not the K-1 had the AA simulator enabled, they don't seem to say, which is a bit odd, because they do provide the pixel shift setting as an alternative option for the K-1. I do suspect it was on, though, because the resolution of the D850 is much better and the moire much worse than the difference in pixel density between the sensors would explain.

I don't understand how folks can say that the resolution is similar between the two. If you select ISO 100, raw, image size 'full', and the rear wall in the scene of the lithography image, you see a very fine, well-defined square pattern with lots of colorful moire in the D850 image, whereas in the K-1 rendering it's all a wash but without the CA artifacts. That said, I agree that lens differences or subtle focusing errors could be the cause as well.
Forum: Pentax DSLR Discussion 10-04-2017, 03:10 PM  
DPReview High ISO Noise D850 vs K-1
Posted By Ikarus
Replies: 29
Views: 1,684
To me, the D850 is visibly sharper than the K-1 in low ISO for raw images. I suspect this is because the K-1 had the AA simulator enabled, whereas the D850 has nothing of the sort. The price to pay for the increase in sharpness is visible in the lithography scene on the left that the D850 turns into a moire and CA feast of epic proportions at ISO100.
Forum: Pentax SLR Lens Discussion 09-29-2017, 12:44 PM  
Blind test: Guess the lens (8 x 135mm)
Posted By Ikarus
Replies: 30
Views: 1,540
Overall, I see very little between them for these two sets. The notable outlier is lens #4, which has a downright nasty looking bokeh in the f/8 set. I'm thinking this might be the Fujita.
Forum: Pentax Price Watch 09-17-2017, 11:37 AM  
20% Off Through RAKUTEN
Posted By Ikarus
Replies: 4
Views: 671
Coupon is apparently dead and no longer advertised on their front page. Looks like they had a low limit on the maximum number of coupon users, even though the expiration date of 9/19 was suggesting it was going to be available to many, and this was just a ploy to get people to sign up on their sh*tty site.
Forum: Pentax Price Watch 09-17-2017, 09:39 AM  
20% Off Through RAKUTEN
Posted By Ikarus
Replies: 4
Views: 671
Good catch, if only it worked!

I get all the way to the payment confirmation page for the 55-300 PLM from Adorama, when I get

"We're sorry! This coupon cannot be applied because the coupon usage limit has been exceed." (sic!)

Seems others have the same issue, see here.
Forum: Winners' Showcase 02-01-2017, 11:08 AM  
February, 2017 Third Place: Bench
Posted By Ikarus
Replies: 20
Views: 757
Bench by Ludger Solbach, on Flickr
Forum: Lens Clubs 08-22-2016, 10:25 AM  
Fisheye Fever Club -- Flaunt your fisheye photos!
Posted By Ikarus
Replies: 2,994
Views: 512,172
The Pentax 10-17 @ 13mm, essentially de-fished
Sand Beach Harbor by Ludger Solbach, on Flickr
Forum: Pentax K-3 05-29-2016, 11:30 AM  
K10d upgrade Do I get a K3 or K1 full frame
Posted By Ikarus
Replies: 26
Views: 2,421
Not in the least. I was responding to the following statement of yours: "The sensor size has no impact on DOF." If that was meant to say "The sensor size has no relevance for DOF when one is not operating at wide open aperture.", we have no disagreement.

---------- Post added 05-29-16 at 11:41 AM ----------



Yes, aka flip-side of the coin. For tele work, APS-C is definitely compelling. For shallow DOF, I'd go with FF.



To me it's less about matching them than knowing your trade-offs and one thing that's important to understand is that they really are significant only for the corner cases (low light, long distance, shallow DOF, high magnification, etc). For everything in between, i.e. the vast majority of shots, people will be hard-pressed to tell the difference between APS-C and FF.
Forum: Pentax K-3 05-28-2016, 10:21 PM  
K10d upgrade Do I get a K3 or K1 full frame
Posted By Ikarus
Replies: 26
Views: 2,421
Sure, except that in order to match FOV and DOF of a FF 50mm f1.4 shot, one needs a 35mm f1.0 on APS-C, so good luck with that!
Forum: Pentax Full Frame 04-23-2016, 02:10 PM  
The High ISO Scam?
Posted By Ikarus
Replies: 111
Views: 9,419
It could be for wildlife, if it is the only way to get the shot. If you don't believe me, then maybe you'll believe Jim Richardson (here for a published ISO 6400 shot and here for some general commentary on the subject.
Forum: Pentax Full Frame 04-14-2016, 11:08 PM  
The High ISO Scam?
Posted By Ikarus
Replies: 111
Views: 9,419
I understand where you're coming from and I agree that if you have the option to fully control your environment, there is little excuse for not shooting at base ISO, but to me, this is not all there is to photography. Many scenarios do not allow for optimally controlling the parameters, for instance by flash not being permitted. There is a whole slew of iconic photos that aren't technically perfect, and which make me thankful that the photographer didn't give a hoot about technicalities. To quote one of the proponents of unshackling the photographer from being a slave to perfection...

:D

As a case in point, just one of many masterpieces ("Rue Mouffetard") by the man himself.
Forum: Pentax Full Frame 04-14-2016, 05:30 PM  
The High ISO Scam?
Posted By Ikarus
Replies: 111
Views: 9,419
For equivalent AOV, DOF and exposure, the focal length and f/stop scale with the crop factor and the ISO with the crop factor squared (since the total light is the same, but the sensor area is 1.5^2 larger for FF, so the light intensity drops by the same amount). So yes, ISO scales up for FF, not down, so if you move to FF, you better get used to using higher ISO settings. Mind you, higher ISO does not imply more noise when changing the format. See for instance here for more details.



It does suffer for sure, but what are the options with the given parameters? You can't open the aperture any wider than 2.8 with this lens, and you can't possibly drop the shutter speed without making things worse. In fact, I wouldn't be surprised if the shot were better with double the ISO for the sake of a faster shutter speed.
Forum: Lens Clubs 04-14-2016, 02:51 PM  
Fisheye Fever Club -- Flaunt your fisheye photos!
Posted By Ikarus
Replies: 2,994
Views: 512,172
The 10-17 at 10mm, just mildly cropped, no distortion correction applied, processed with Nik Silver Efex for drama. This is such a fun little lens!

Memorial Point by Ludger Solbach, on Flickr
Forum: Pentax Full Frame 04-14-2016, 09:39 AM  
The High ISO Scam?
Posted By Ikarus
Replies: 111
Views: 9,419
Unlikely. In order to match the shot, you'd be shooting the K-1 at 200mm, f/4, 1/200s, ISO28800. How do you think you'd be able to drop that to ISO3000? In general, I believe high ISO gets all the bad rap for poor image quality in difficult conditions. In the case of this kart-racing shot, the shutter speed is borderline adequate at best. Without the motion blur, you could do a much better job at cleaning up that high ISO noise.
Forum: Pentax Full Frame 04-13-2016, 05:31 PM  
The High ISO Scam?
Posted By Ikarus
Replies: 111
Views: 9,419
I respectfully disagree, see below. While these aren't technically perfect shots by any stretch of imagination, I would definitely call them good enough for many purposes, including printing at moderate sizes. If it's between getting or not getting the shot, high ISO can save the day sometimes. Even I would draw the line at around ISO 12800, though.

K-01 at ISO 3200
Cheshire Cat / Flower by Ludger Solbach, on Flickr

K-3 at ISO 4000
Furrowed by Ludger Solbach, on Flickr

K-x at ISO 3200
Hugs and Kisses by Ludger Solbach, on Flickr
Forum: Pentax K-1 04-08-2016, 03:35 PM  
The wait for the dream machine.
Posted By Ikarus
Replies: 40
Views: 3,001
For the equivalent shot on FF you have no choice but stopping down to f' = f*1.5 in order to match an APS-C camera in DOF and AOV, but diffraction at the equivalent DOF and AOV is independent of sensor size, so the K-1 will do about as well at f/16, as the K-3 does at f/11.
Forum: Pentax K-1 04-08-2016, 10:36 AM  
The wait for the dream machine.
Posted By Ikarus
Replies: 40
Views: 3,001
Ok, it seems you also changed the print size from 10" to 24" in order to get such low limits. Anyway, the key point here is that one should not expect the K-1 at f/22 to outperform the K-3 at f/11 in terms of diffraction. So, to those folks who feel like their lowly K-3 or K-5 is not not up to snuff anymore with the K-1 on the horizon, I say this - just go out and shoot, it really ain't all that bad. :lol:
Forum: Pentax K-1 04-08-2016, 01:26 AM  
The wait for the dream machine.
Posted By Ikarus
Replies: 40
Views: 3,001
If you enter the data of the K-1 and the K-3 in the calculator here, you'll find that the K-1 at f/22 is closer to being diffraction limited than the K-3 at f/11.



Sure, that's why it makes no sense to compare diffraction between formats at anything other than the equivalent focal length and f-stop.
Forum: Pentax K-1 04-07-2016, 04:07 PM  
The wait for the dream machine.
Posted By Ikarus
Replies: 40
Views: 3,001
The diffraction-limited depth of field is constant for all sensor sizes, so if it already hits you at f11 on APS-C, it will hit you even harder at f22 on FF.
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