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04-07-2016, 06:57 PM   #61
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QuoteOriginally posted by osv Quote
optical bench tests are done at infinity, imatest needs to have the chart close enough to fill the frame, no guarantees how it'll look with radical changes in distance.

ultimately, i think that you have to test it how it'll be used, the landscape pics that posted are how i test lenses, at all apertures.

so i know that the m28/3.5 has minimal field curvature at 100+ yards, it has a flat focus field, minimal ca, and i know the apertures that it's usable at.

i've also tested a couple of dozen other 28mm legacy lenses, standing at that exact same spot, focusing at the exact same target; no lens has been able to match it.

you've seen the pic, it looks decent on the right side even at 100%, but at extreme distances, the right side goes soft, depending on how far it was focused into the scene... got to test it how it'll be used.
Please tell me you're joking. I asked you how far away to look at a PHOTOGRAPH and you come back and talk about charts. Learn photography not how to be a gear head. The obsession with pixel peeping and charts is killing the aesthetic and artistic elements in any photographic discussion.

04-07-2016, 07:03 PM   #62
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QuoteOriginally posted by 2351HD Quote
OSV, you said it, you said the priority is to get a lens that can take a landscape shot at a wider aperture.....

Any lens will perform better at F11 if it gives you the DOF that you need.
what if you don't need that small increase in dof to get the shot?

for example, look at all of these great itshimitis landscape shots: https://www.pentaxforums.com/forums/76-non-pentax-cameras-canon-nikon-etc/110...ughts-358.html

exactly which of those pics are you going to need to stop down more than f/8? most of 'em don't have any foreground objects at all.

especially if you had his batis 25 that thing kicks butt all the way across the frame at f/5.6, or even wider.

---------- Post added 04-07-16 at 07:05 PM ----------

QuoteOriginally posted by itshimitis Quote
Please tell me you're joking. I asked you how far away to look at a PHOTOGRAPH.
you responded to post about charts.

i've already posted PHOTOGRAPHS to this thread, lol
04-07-2016, 07:29 PM   #63
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QuoteOriginally posted by 2351HD Quote
There's no point having a sharp lens at f5.6 if you don't have the required depth of field.

I just don't see the point of your whole entire pitch here in this thread.
maybe you can't see the point because you've never actually looked at the dof... here is the difference, f/8 vs. f/11, it's maybe two feet more dof? versus lower resolution across the frame, loss of light and dr, visible diffraction, etc... it'll probably be less than two feet difference at the minimum focusing distance:
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04-07-2016, 08:58 PM   #64
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I just realized you are that same guy who likes to share the charts. Why do you keep following us?


04-07-2016, 11:29 PM   #65
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QuoteOriginally posted by osv Quote
maybe you can't see the point because you've never actually looked at the dof... here is the difference, f/8 vs. f/11, it's maybe two feet more dof? versus lower resolution across the frame, loss of light and dr, visible diffraction, etc... it'll probably be less than two feet difference at the minimum focusing distance:
I am well aware of dof champ. No need to be a smart ar5e.

There is a big difference as to what a DOF calculator says will be acceptably sharp and what actually "IS" acceptably sharp in the real world. These calculators are well off in my experience.

Anyway, keep your charts and you will do well.

Cheers
04-08-2016, 03:10 AM   #66
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I like a hearty debate with the best of them, but, erm... Well, is it just me, or has this (and a few other 'debates' recently) become a little, well, low on the value:bollocks ratio?
04-08-2016, 04:05 AM - 1 Like   #67
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*munches on popcorn*

@MikeSF, you want some too?
04-08-2016, 04:09 AM   #68
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QuoteOriginally posted by Digitalis Quote
*munches on popcorn*

@MikeSF, you want some too?
Salted please.

04-08-2016, 04:50 AM   #69
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QuoteOriginally posted by 2351HD Quote
OSV, you said it, you said the priority is to get a lens that can take a landscape shot at a wider aperture.....

Any lens will perform better at F11 if it gives you the DOF that you need. There's no point having a sharp lens at f5.6 if you don't have the required depth of field.

I just don't see the point of your whole entire pitch here in this thread.


I don't think the case for better wide apertures was presented particularly well. OSV's statements assume facts not in evidence. The following may not be any better since I don't traffic in the jargon of photography much but I'll take a stab and is directed at the forum in general without a presumption of the level knowledge/expertise of each reader.


It is quite possible for a lens to be sharp across the frame wide open, even at f1.4. The Zeiss Otus series proves this and is famous for this. I was first introduced to wide open "landscape shooting" relatively recently (where "landscape shooting" presumes not only good sharpness from front to back but good sharpness across the frame into the corners and edges, the latter being a function of how well lens aberrations are handled by the designers) with the Canon 24-70 II which can be used at 24mm/ f2.8 (wide open) and produces acceptably sharp corners/edges. This lens was a huge eye-opener. If one's composition is at infinity distance across the frame (nature's flat wall), no DoF essentially, then such lenses can render such compositions sharp (in focus) across the frame. When objects are placed closer than infinity to the shooting position, then DoF comes into play and one must stop down to render this object "in focus". Obviously, how much one has to stop down is determined by how close that object(s) are placed to the shooting position (assuming one wants good front to back sharpness). What one does not want to do, if possible, is to stop down just to fix lens aberrations as in the case of compositions featuring infinity across the frame. Nothing about lens design demands that a lens' "sharpness" (in focus) must drop off in the corners at wider or wide open pertures other than meeting a price point and/or customer satisfaction.


Why is good corner/edge performance good? It avoids unnecessary stopping down to fix lens aberrations which, depending on how bad the aberration is, could force another issue, diffraction, upon the image. Diffraction is more of a concern for smaller sensors (where diffraction at f8 is visible during pixel peeping sessions). Amazingly, I have stopped down to f32 on the 645z without the visible softening associated with f16 on a FF system (impressionistic not scientifically derived)..
04-08-2016, 05:02 AM   #70
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QuoteOriginally posted by rfkiii Quote
Why is good corner/edge performance good? It avoids unnecessary stopping down to fix lens aberrations which, depending on how bad the aberration is, could force another issue, diffraction, upon the image. Diffraction is more of a concern for smaller sensors (where diffraction at f8 is visible during pixel peeping sessions). Amazingly, I have stopped down to f32 on the 645z without the visible softening associated with f16 on a FF system (impressionistic not scientifically derived)..
Aberrations do not cause diffraction.
Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks

As the opening becomes smaller, diffracted light becomes a larger percentage of the light collected by the sensor at each location. But it is true, the larger the sensor, the less affected it is by diffraction at a given ƒ-stop. However probably not when you equalize for depth of field.
04-08-2016, 05:44 AM - 1 Like   #71
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QuoteOriginally posted by normhead Quote
Aberrations do not cause diffraction.
Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks

As the opening becomes smaller, diffracted light becomes a larger percentage of the light collected by the sensor at each location. But it is true, the larger the sensor, the less affected it is by diffraction at a given -stop. However probably not when you equalize for depth of field.


I wasn't suggesting a direct causal effect but there is an indirect effect. Stopping down has pros and cons. The pro for landscape being that stopping down brings objects into focus (including edges and corners rendered out of focus by lens aberrations) but stopping down can also bring on diffraction. If one's composition has no close objects and the only reason to stop down is to fix out of focus corners and edges, then a better designed (and more expensive ) lens would eliminate this need and as an extra benefit, avoid possible diffraction issues.
04-08-2016, 06:05 AM   #72
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QuoteOriginally posted by rfkiii Quote
I wasn't suggesting a direct causal effect but there is an indirect effect. Stopping down has pros and cons. The pro for landscape being that stopping down brings objects into focus (including edges and corners rendered out of focus by lens aberrations) but stopping down can also bring on diffraction. If one's composition has no close objects and the only reason to stop down is to fix out of focus corners and edges, then a better designed (and more expensive ) lens would eliminate this need and as an extra benefit, avoid possible diffraction issues.
Exactly.
04-08-2016, 07:27 AM   #73
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QuoteOriginally posted by itshimitis Quote
Salted please.
QuoteOriginally posted by Digitalis Quote
*munches on popcorn*

@MikeSF, you want some too?
& butter
04-08-2016, 08:47 AM - 2 Likes   #74
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QuoteOriginally posted by normhead:
Or maybe it's just you.
Norm,

I've been thinking about what went wrong yesterday in the posting, and I realize the first mistake I made was unnecessarily taking personal offense at a statement, then overreacting and writing a response that was defensive, prideful, and snippy. I know better than that. I was wrong. No excuses. And I apologize to you.

I sent an apology to Bob L also (Bob, thank you for your gracious PM reply). To anyone else reading the thread that was offended by my immature attitude in those posts, I apologize as well.

Sincerely,
Ross
04-08-2016, 11:24 AM - 2 Likes   #75
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These sorts of discussions tend to devolve into folks who focus on test charts/mtf scores/camera specs and those who are about the final image. There is probably a place for both, but to me the image is the goal.

When I look at the "Post Your MF Images" thread, I am constantly amazed, but truthfully, it isn't the camera or the glass that wows me, but the skill of the photographers -- both in capturing light and gently post processing it in a way that brings out the best in a given image. Not every photo is perfect, but overall they are at a higher level because of those who are using the cameras and not because of the cameras.

Changing number of megapixels could help when printing bigger, but I don't know that it really changes anything else. Personally, I want better pixels, not more of them, but each to his or her own.
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