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Author Topic: 645D - Are my expectations unreasonable? Near-edges very soft at infinity [imgs]  (Read 8094 times)
smoody
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« on: January 05, 2011, 04:43:39 PM »
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I'm on my second 645D. I am about to return it or exchange it for a third, but wanted to get some consensus on what I'm seeing. Both of my 645Ds paired with the new 55mm lenses exhibited similar softness approaching the edge. Here are the facts:

- When shooting city landscapes (my standard real-world focused-as-infinity resolution test), I noticed that anything left or right of center was very soft.

- To produce something close to an apples-to-apples comparison, I took two 645D shots. The clear one, as you might expect, is from the center of the image. After taking the clear one, I panned my camera/tripod head to the right so that the exact same buildings were now on the left-side of the image -- not the extreme left edge, just the left side.

- Both shots were taken without window glass between the 645D and the scene being shot. Both exposed at f/5.6, 1/750th of a second, using the new 55mm, tripod mounted, manually focused at same point (infinity), pre-shot mirror lockup via 2 second timer, captured as DNGs and converted using ACR (but out-of-camera JPEGS looked essentially the same minus difference to color balance). Both shots are completely in-focus at the center of the frame. Both are 100% crops. Both were sharpened -- perhaps to fault -- to see how much detail I can pull out of the crops.

Without further delay...

The center crop:




The same buildings, but on the left side of the image:



The edge seems very smeared to me. I emailed the images to Pentax tech support and they said that the cannot say if the softness I am seeing is within tolerances and pretty much refuse to look at anything other than a shot of a test chart, which I understand, but a test chart can't detect any defects shot at infinity. I know there are very few people with 645Ds out there right now, but...

- For those with 645Ds, are you seeing the same thing? It is only very noticeable to me focused at infinity. Shots taken on the street seem okay, but, of course, depth of field comes into play in that case.

- For those with other medium format systems, is this fairly typical of near-edge sharpness at near-optimal f/stop with your body/back/lenses?

I'd normally assume that I received a bad component, but as this is my second 645D, I'm wondering if it's a limitation of the optics and/or the 645D's ability to resolve properly across the entire sensor at infinity.

For completely useless grins, here is the same shot that was blurry with the 645D (from left-side of image) taken with a Leica M9 in combination with Leica's cheapest lens, the 50mm Summarit (which, coincidentally, costs as much as the Pentax 55mm -- at least at the time I bought it) -- same f/stop, shutter speed, etc.



Thanks,

    Scott





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ErikKaffehr
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« Reply #1 on: January 05, 2011, 05:09:34 PM »
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Hi,

Sorry to say, Lloyd Chambers tested the Pentax 645D and albeit he was very positive to the camera he didn't find satisfaction in the 55/2.8. He tested two samples and neither impressed in the edges/corners. Most other lenses he tested were good.

http://www.diglloyd.com/prem/prot/DAP/Pentax645D/compare-Canon5DM2-55mm.html

"Diglloyd" is a pay site, but I'd suggest that the money is well invested.

Best regards
Erik


I'm on my second 645D. I am about to return it or exchange it for a third, but wanted to get some consensus on what I'm seeing. Both of my 645Ds paired with the new 55mm lenses exhibited similar softness approaching the edge. Here are the facts:

- When shooting city landscapes (my standard real-world focused-as-infinity resolution test), I noticed that anything left or right of center was very soft.

- To produce something close to an apples-to-apples comparison, I took two 645D shots. The clear one, as you might expect, is from the center of the image. After taking the clear one, I panned my camera/tripod head to the right so that the exact same buildings were now on the left-side of the image -- not the extreme left edge, just the left side.

- Both shots were taken without window glass between the 645D and the scene being shot. Both exposed at f/5.6, 1/750th of a second, using the new 55mm, tripod mounted, manually focused at same point (infinity), pre-shot mirror lockup via 2 second timer, captured as DNGs and converted using ACR (but out-of-camera JPEGS looked essentially the same minus difference to color balance). Both shots are completely in-focus at the center of the frame. Both are 100% crops. Both were sharpened -- perhaps to fault -- to see how much detail I can pull out of the crops.

Without further delay...

The center crop:




The same buildings, but on the left side of the image:



The edge seems very smeared to me. I emailed the images to Pentax tech support and they said that the cannot say if the softness I am seeing is within tolerances and pretty much refuse to look at anything other than a shot of a test chart, which I understand, but a test chart can't detect any defects shot at infinity. I know there are very few people with 645Ds out there right now, but...

- For those with 645Ds, are you seeing the same thing? It is only very noticeable to me focused at infinity. Shots taken on the street seem okay, but, of course, depth of field comes into play in that case.

- For those with other medium format systems, is this fairly typical of near-edge sharpness at near-optimal f/stop with your body/back/lenses?

I'd normally assume that I received a bad component, but as this is my second 645D, I'm wondering if it's a limitation of the optics and/or the 645D's ability to resolve properly across the entire sensor at infinity.

For completely useless grins, here is the same shot that was blurry with the 645D (from left-side of image) taken with a Leica M9 in combination with Leica's cheapest lens, the 50mm Summarit (which, coincidentally, costs as much as the Pentax 55mm -- at least at the time I bought it) -- same f/stop, shutter speed, etc.



Thanks,

    Scott






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tho_mas
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« Reply #2 on: January 05, 2011, 05:21:43 PM »
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I'm on my second 645D...
I do not own the camera but have seen much better shots/crops, also with the 55mm lens. And even if I would not have seen any samples it's pretty clear that there is something wrong.
I think either the lens is totally decentered or the sensor mounting is out of perpendicualr alignement. Actually it looks like "swing" on the sensor... but if there was the same issue on the first body with the exact same lens (?) it's probably the lens.
And you are right... sensor misalignement or a decentered lens are better checked at infinity...
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ErikKaffehr
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« Reply #3 on: January 05, 2011, 05:28:55 PM »
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Hi,

Have you noticed the amount of Moiré and aliasing on the sharp Pentax 55/2.8 shot and also on the Leica? The sharpness is impressive but aliasing is the price you pay.

Best regards
Erik


I'm on my second 645D. I am about to return it or exchange it for a third, but wanted to get some consensus on what I'm seeing. Both of my 645Ds paired with the new 55mm lenses exhibited similar softness approaching the edge. Here are the facts:

- When shooting city landscapes (my standard real-world focused-as-infinity resolution test), I noticed that anything left or right of center was very soft.

- To produce something close to an apples-to-apples comparison, I took two 645D shots. The clear one, as you might expect, is from the center of the image. After taking the clear one, I panned my camera/tripod head to the right so that the exact same buildings were now on the left-side of the image -- not the extreme left edge, just the left side.

- Both shots were taken without window glass between the 645D and the scene being shot. Both exposed at f/5.6, 1/750th of a second, using the new 55mm, tripod mounted, manually focused at same point (infinity), pre-shot mirror lockup via 2 second timer, captured as DNGs and converted using ACR (but out-of-camera JPEGS looked essentially the same minus difference to color balance). Both shots are completely in-focus at the center of the frame. Both are 100% crops. Both were sharpened -- perhaps to fault -- to see how much detail I can pull out of the crops.

Without further delay...

The center crop:




The same buildings, but on the left side of the image:



The edge seems very smeared to me. I emailed the images to Pentax tech support and they said that the cannot say if the softness I am seeing is within tolerances and pretty much refuse to look at anything other than a shot of a test chart, which I understand, but a test chart can't detect any defects shot at infinity. I know there are very few people with 645Ds out there right now, but...

- For those with 645Ds, are you seeing the same thing? It is only very noticeable to me focused at infinity. Shots taken on the street seem okay, but, of course, depth of field comes into play in that case.

- For those with other medium format systems, is this fairly typical of near-edge sharpness at near-optimal f/stop with your body/back/lenses?

I'd normally assume that I received a bad component, but as this is my second 645D, I'm wondering if it's a limitation of the optics and/or the 645D's ability to resolve properly across the entire sensor at infinity.

For completely useless grins, here is the same shot that was blurry with the 645D (from left-side of image) taken with a Leica M9 in combination with Leica's cheapest lens, the 50mm Summarit (which, coincidentally, costs as much as the Pentax 55mm -- at least at the time I bought it) -- same f/stop, shutter speed, etc.



Thanks,

    Scott






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tho_mas
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« Reply #4 on: January 05, 2011, 05:35:33 PM »
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Have you noticed the amount of Moiré and aliasing on the sharp Pentax 55/2.8 shot and also on the Leica? The sharpness is impressive but aliasing is the price you pay.
that is one very helpful comment to sort out the issues.
And it sure required another full quote of the OP.
 Huh
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BernardLanguillier
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« Reply #5 on: January 05, 2011, 05:49:24 PM »
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This totally looks like a lens issue, doesn't it?

The Pentax 55mm f2.8 appears to be an average performer at best, but my question would be at what aperture you shot?

I would expect f8 to be better than this.

Regardless, you should try to other lenses like the 75mm of 120 f4 macro known to be excellent (at least in their non AF versions).

Cheers,
Bernard
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A few images online here!
DeeJay
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« Reply #6 on: January 05, 2011, 08:02:46 PM »
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Yeah it looks like a lens issue to me for sure. Doesn't look great either!
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bradleygibson
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« Reply #7 on: January 05, 2011, 11:26:28 PM »
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Bernard,

Both exposed at f/5.6, 1/750th of a second, using the new 55mm, tripod mounted, manually focused at same point (infinity), ...

Scott, I don't think your expectations are unreasonable.  Your technique seems fine.  I agree with the others on this thread that the lens doesn't seem to be cutting it.  It might be just your copy or it might be the lens design itself.  Do you have other focal lengths to try?
« Last Edit: January 05, 2011, 11:28:24 PM by bradleygibson » Logged

Leping
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« Reply #8 on: January 05, 2011, 11:56:54 PM »
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Lloyd's findings in short (DAP is subscription based but a lot conclusions are in the blogs like this):

http://diglloyd.com/diglloyd/2011-01-blog.html#blog20100104Pentax120f4

The new 55mm and 45mm FA are bad out of the center 1/2 (55mm) and 2/3 (45mm) area.

The 75mm and 200mm are very good at least (hard to focus).

The 45-85mm zoom is excellent, and way outperforms the 45 and 55 primes.  (no surprise -- after careful testing I sold all my Pentax 67 prime lenses in the range of the two zooms.)

The 120mm macro is outstanding, razor sharp corner to corner even wide open at f/4.

He is going to test more (150mm, 80-160mm zoom, and some Pentax 67 lenses through the adapters, at least).

Else where on the web you can find sample images from the 35mm and the 33-55mm zoom.  They look fine and 16-9.net tested and found the Pentax 645 35mm the best wide angle in MF field.  Now lacking are sample images and reviews of the 55-110 and the 150-300 zooms, and the long (300mm ED IF, 400mm ED IF, and 600mm ED IF) optics.

Pentax released a new firmware (V1.0.1) for the 645D to support SDXC cards, and promised firmware changes in the future for tethered shooting as well as new lenses including a new wide angle, rumored a 25mm/f4.

About the 67 adapter on 645 and 645D -- you can use the 67 lenses exactly as the 645 MF (A) lenses:

“Pentax has two medium format camera lines, the Pentax 67 and the Pentax 645. Unique among camera makers,
Pentax has designed the systems so that the lenses from the 6X7 camera can also be used on the 645 body. They
manufacture an adaptor for this that retains autodiaphram and open-aperture metering capability. Put it on a 645
body and you can use all your 67 lenses pretty much as normal. (Contax allows their 645 lenses to be used on the
N series 35mm cameras. Pentax has an adaptor that allows medium format to 35mm as well, but in this case
autodiaphram is lost.)”

You can also buy small gadgets like this:

Pentax O-RC1 Remote Control

"A simple item that didn’t come with the 645D camera was a remote control.  The Pentax O-RC1 is a simple device that allows you to fire the shutter without pushing the shutter release button. This is great for self portraits and family photos as it avoids the self-timer dash. More importantly for me,  it means I can eliminate any micro wobble that may occur when pressing the shutter release button on a tripod mounted camera. As a bonus the remote control is waterproof, which in rain soaked Okinawa is probably a good idea.

The remote control also works with other 2010 Pentax cameras including the Optio W90."

Lloyd's DAP and other detailed paid references (such as digital infrared) are worth the subscription cost to my opinion.


« Last Edit: January 06, 2011, 12:16:58 AM by Leping » Logged

ErikKaffehr
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« Reply #9 on: January 06, 2011, 12:10:02 AM »
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Hi,

You are absolutely correct!

On the other hand I posted a comment on Diglloyd's findings with two other samples on the same lens, after actually rereading his review. They were pretty much similar.

I couldn't resist commenting on the Moiré, because it's a very good example of it showing up but also because I have observed a lot of Moiré when I was Pixel peeping the few raw files that have been published from MF cameras. Nothing unexpected, it's the price of working without an AA filter. It also indicates that the lens outresolves the sensor, even if the correct terminology may be that it has high MTF at Nyquist limit.

By the way, most of the lenses Diglloyd has tested on the P645D are fine. He found the 55/2.8 and his sample of the 45/2.8 lacking. But he found 45-85, 75/2.8 and 120/4 very good. The 200/4 (non AF) was very difficult to focus manually.

Best regards
Erik


that is one very helpful comment to sort out the issues.
And it sure required another full quote of the OP.
 Huh
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John R Smith
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« Reply #10 on: January 06, 2011, 02:24:10 AM »
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What seems quite extraordinary to me is that Pentax are shipping their flagship camera with what is quite evidently a sub-standard optic. If any of my 'Blad lenses were as poor as that I would weep. Surely the camera should be offered with a decent quality standard prime (whatever that would be - the 75mm f2.8?). It is even more puzzling because we know that Pentax can produce some really fine lenses.

John
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« Reply #11 on: January 06, 2011, 02:39:38 AM »
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What seems quite extraordinary to me is that Pentax are shipping their flagship camera with what is quite evidently a sub-standard optic.

It can be targeted to portrait shooting since the center sharpness is very high (told from the amount of moiré), on the par of the Leicas (S2).  The performance also improves when focused to nearby.  The 75mm/2.8 is good.  On the other hand Lloyd have showed at least some of the Hasselblad lenses are far worse than the 40-60MP sensor demands.  On the film days I always challenged Hasselblad shooters on the light tables through a 22x loupe, and my Pentax chromes always won.

All the existing Pentax 67 lenses should perform flawlessly all the way to the corners, an advantage most other systems could not match.  I posted a 100% resolution target shot off a 5DMKII to show even the Pentax zooms can outperform the best 35mm lenses widely open.
« Last Edit: January 06, 2011, 02:53:49 AM by Leping » Logged

John R Smith
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Still crazy, after all these years


« Reply #12 on: January 06, 2011, 03:02:31 AM »
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It can be targeted to portrait shooting since the center sharpness is very high (told from the amount of moiré), on the par of the Leicas (S2).  

Why on earth would you choose to shoot portraits with a 55mm? Surely its natural role is for landscape and architecture, just the subjects which will suffer from poor sharpness across the frame.

John
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Rob C
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« Reply #13 on: January 06, 2011, 03:18:38 AM »
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Why on earth would you choose to shoot portraits with a 55mm? Surely its natural role is for landscape and architecture, just the subjects which will suffer from poor sharpness across the frame.

John




Exactly my thoughts John, but we are from a different generation, I suspect. To moderns, distortion is cool.

As for 6x7 format lenses beating 35mm format lenses, that's into science fiction. The whole problem associated with people making the step up from 35mm cameras to medium format (top quality in both cases) was that they assumed that they were multiplying 35mm quality by the film size factor, when the truth is that 35mm formats are such superlative peformers precisely because the designers only have to cover a small area with the 35mm format, and simply can't achieve the same degree of quality over the larger area mf presents... The only real advantage from mf has always been that of tonality. Period.

Rob C
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eronald
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« Reply #14 on: January 06, 2011, 03:24:17 AM »
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that is one very helpful comment to sort out the issues.
And it sure required another full quote of the OP.
 Huh

That's the way this forum works: We use their shots to help inform us generally.

Edmund
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« Reply #15 on: January 06, 2011, 04:18:02 AM »
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The only real advantage from mf has always been that of tonality. Period.

Where did detail go?
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hjulenissen
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« Reply #16 on: January 06, 2011, 05:14:52 AM »
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The only real advantage from mf has always been that of tonality. Period.
Tonality have always been a vague term to me. Is it something that one can read out of dxo measurements, or something that can be clearly pointed to in a side-by-side comparision of images from cameras that "good" tonality vs "bad" tonality?

-h
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ErikKaffehr
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« Reply #17 on: January 06, 2011, 06:18:07 AM »
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+1

Tonality have always been a vague term to me. Is it something that one can read out of dxo measurements, or something that can be clearly pointed to in a side-by-side comparision of images from cameras that "good" tonality vs "bad" tonality?

-h
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amsp
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« Reply #18 on: January 06, 2011, 06:57:58 AM »
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Tonality have always been a vague term to me. Is it something that one can read out of dxo measurements, or something that can be clearly pointed to in a side-by-side comparision of images from cameras that "good" tonality vs "bad" tonality?

-h

I've always found the difference in tonality between 35mm and MFD to be very obvious once you start working with the images in post production. My old P25 still outperforms my 5d mkII by far in this regard. But I guess it's mainly in heavy duty post like fashion and advertising you'll notice this the most.

« Last Edit: January 06, 2011, 07:00:56 AM by amsp » Logged
tho_mas
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« Reply #19 on: January 06, 2011, 07:17:14 AM »
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I couldn't resist commenting on the Moiré, because it's a very good example of it showing up but also because I have observed a lot of Moiré when I was Pixel peeping the few raw files that have been published from MF cameras. Nothing unexpected, it's the price of working without an AA filter.
Why couldn't you resist? Is it some kind of sports for you to point out issues with MFD?
Seems so...
The OP referred to a lens or sensor issue... not to the ease of use of a non AA filtered vs. an AA filtered camera.

if you look at the first of the 2 samples available here http://www.leaf-photography.com/products_aptus212r.asp you will find that moiré isn't an issue.
The shot was taken with one of the sharpest lenses available and the motif is extremely prone to show moiré.
So obviously it depends on the pattern-size of the subject and the pixel pitch of the sensor (the Apt.12's pixel pitch is 5.2microns).

I do not negate the issue of moiré with non AA filtered sensors, not at all (why would I... I have to deal with it quite often).
But unless you shoot fabrics (or similar subjects) it's mostly an easy fix. In those landscape or cityscape shots it's often not an issue at all (depends on the actual motif, of course).
Moiré can also totally ruin a shot... in this case you have to either stop down (to f22 or so ... at the price of less sharpness... and maybe also at the price of more DOF than you actually wanted to achieve) ... or use an appropriate camera.

I think generalized statements require some kind of substantiated experience with the subject the respective statement refers to.
Looking at some arbitrary samples available online won't do.


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