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11-28-2014, 09:48 AM   #646
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QuoteOriginally posted by Mistral75 Quote
You're welcome.

Considering their protocol "The principal idea is to take the AF focus distance as a rough guidance and do several manual focus iterations within a radius of roughly +/-20% around the suggested focus distance. The images with the highest resolution are then analyzed and presented in the final MTF chart.", I do not see how they could miss a lens's field curvature.

I must confess I have a hard time understanding what you mean when you write "Field curvature is not something a lens suffers from, it's a feature, and a good one, if you ask me."
If a particular lens has field curvature such that the DOF in the corners of an image is closer to the camera, I may actually agree. Because then it can actually help to compensate for focus error when using the focus-and-recompose technique with a wide-angle lens.

But I believe that in most cases, the DOF of a lens with field curvature actually moves away from the camera in the corners, i.e. the exact opposite. So it would only make things worse.

11-28-2014, 10:00 AM   #647
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Simply because I don't photograph focus charts a lot.

I prefer to photograph the world as I see it, in three dimensions, not flat. When I watch a wall in real life, I see the objects in the corner as further away than a centered object. You loose that dimension when using a flat field lens. And that's why good lens designers usually makes lenses with field curvature, ON PURPOSE.

The exception is macro lenses, they usually are designed with flat field on purpose. Because they are intended for a different purpose, to reproduce the word differently.
11-28-2014, 10:17 AM   #648
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QuoteOriginally posted by LensBeginner Quote
What can we infer from that "large diameter" wording? Also "large(r) image circle"?
Must/gotta be!
11-28-2014, 10:25 AM   #649
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Originally posted by LensBeginner
QuoteQuote:

What can we infer from that "large diameter" wording? Also "large(r) image circle"?
QuoteOriginally posted by Mikesul Quote
Must/gotta be!
It simply means the 16-85mm won't have the excessive vignetting shown by the 18-135mm.

11-28-2014, 10:31 AM   #650
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QuoteOriginally posted by audiobomber Quote
It simply means the 16-85mm won't have the excessive vignetting shown by the 18-135mm.
The 'Large diameter telephoto zoom' has nothing to do with the 16-85mm f/3.5-5.6, it's the name of one of the two mock-ups shown at Photokina, corresponding to a 70-200ish f/2.8 lens.

11-28-2014, 10:35 AM   #651
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QuoteOriginally posted by Mistral75 Quote
The 'Large diameter telephoto zoom' has nothing to do with the 16-85mm f/3.5-5.6, it's the name of one of the two mock-ups shown at Photokina, corresponding to a 70-200ish f/2.8 lens.
And that is a HUGE looking lens!
11-28-2014, 11:10 AM   #652
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It still looks a pretty poor lens ...



DA 16-85 at 26mm f/7.1

??? Isuien Garden ?? 2014 ? HD PENTAX-DA 16-85mm F3.5-5.6ED DC WR ?????????? - ??????

Some of the sample shots are really bad - click on the small thumbnails to see the full size images.

Last edited by kh1234567890; 11-28-2014 at 11:20 AM.
11-28-2014, 11:21 AM   #653
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QuoteOriginally posted by kh1234567890 Quote
DA 16-85 at 26mm f/7.1
Poor lighting, and moss. I hate moss. I have been trying to take a good picture of moss for at least 5 years. Moss exudes some sort of optical defense system that causes all cameras to take soft pictures. I think it was originally a defense system against reindeer so they would get confused and not eat it.

But no, not a great image. Still waiting to see some taken in good light and of subjects that make it easier to evaluate the lens.

11-28-2014, 11:21 AM   #654
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Please don't post gigantic files like that directly at the forum. Takes ages to load if you are on a bad connection, and makes large bills if you are at a phone.

Make links, or downsize.
11-28-2014, 12:43 PM   #655
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QuoteOriginally posted by Fototim Quote
Simply because I don't photograph focus charts a lot.

I prefer to photograph the world as I see it, in three dimensions, not flat. When I watch a wall in real life, I see the objects in the corner as further away than a centered object. You loose that dimension when using a flat field lens. And that's why good lens designers usually makes lenses with field curvature, ON PURPOSE.

The exception is macro lenses, they usually are designed with flat field on purpose. Because they are intended for a different purpose, to reproduce the word differently.
I also prefer to photograph the world as I see it, but I am puzzled by how field curvature is of any consequence to that. I think you might be refering to barrel distortion instead. And indeed some lenses are designed with deliberate barrel distortion (fish-eye lenses).

But what we are talking about here - or at least what I think we are talking about - is curvature of the focus plane. E.g. you focus at 10 meters, take a photo, and find that the bird in the corner of your frame, which was also at 10 meters distance from your camera, is not sharp. Instead, some stupid lamp post at 13 meters is.
11-28-2014, 01:08 PM - 1 Like   #656
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One more sample shot withe 16-85mm on a K-3

11-28-2014, 01:15 PM   #657
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QuoteOriginally posted by Mistral75 Quote
The 'Large diameter telephoto zoom' has nothing to do with the 16-85mm f/3.5-5.6, it's the name of one of the two mock-ups shown at Photokina, corresponding to a 70-200ish f/2.8 lens.
Sorry, I lost the trail of the thread. I also think the 70-200ish will be FF.
11-28-2014, 01:20 PM   #658
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QuoteOriginally posted by Fototim Quote
Simply because I don't photograph focus charts a lot.

I prefer to photograph the world as I see it, in three dimensions, not flat. When I watch a wall in real life, I see the objects in the corner as further away than a centered object. You loose that dimension when using a flat field lens. And that's why good lens designers usually makes lenses with field curvature, ON PURPOSE.

The exception is macro lenses, they usually are designed with flat field on purpose. Because they are intended for a different purpose, to reproduce the word differently.
I attached 1 shoots (not very good but that for showing the problem) and 2 crops. 1 center and one border crop. This shoot as the problem and it is not a wall // to the camera. In fact it is almost as plane as a wall but not parallel to focal plane.

Field curvature at this level is not on purpose. On FA77 I never have the problem even through it is a lens known to have been designed to be pleasing and not give highest possible resolution numbers. Many thing are under corrected on purpose. But FA77 is tele, with almost no distorsion and no field curvatuve. At f/8 everything is razor sharp borders to borders.

But as you can see on theses DA15 pictures really show the DA15 can be quite soft on border in bad cases. I don't need the crop personnaly, I notice it at normal viewing size. On the example it seems that if focus is put near infinite on center, border are not focussed on infinite and subjects futher away are really soft.

I think I need to investigate more, but if somebody can explain how to solve this issue (I have heard here to use hyperfocal distance ?) I'am glad to ear.
Attached Images
View Picture EXIF
PENTAX K-3  Photo 
View Picture EXIF
PENTAX K-3  Photo 
View Picture EXIF
PENTAX K-3  Photo 
11-28-2014, 01:38 PM   #659
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Here another example, where there no subject that much futher away from the focus point... And the focus point also not as distant. The border are soft but overall you don't notice it if you don't crop and the crop while not very good, are already far better.
Attached Images
View Picture EXIF
PENTAX K-3  Photo 
View Picture EXIF
PENTAX K-3  Photo 
11-28-2014, 01:46 PM   #660
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Ok. Technically you are right. Let me rephrase mysef.

Field curvature is a aberration, that is tried corrected to a certain point in most lens designs.

But it when field curvature is well controlled, it is also a feature. I hope I explained the reasons in previous post.
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