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12-02-2011, 04:20 PM - 1 Like   #1
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Q + FA* 300 f4.5 Examples

Hi All,

Finally got some sun, but it's getting colder fast. . . I was able to get out to the Nature Center, and shoot the FA* 300 f4.5 with the Q in the same setting as the previous tests. All were shot with this combination, jpeg ***, Natural with Sharpness and Contrast set to -4, ISO 125, and at f4.5, only the shutter speeds varied between 1/320 and 1/640. All were shot from a lightweight tripod. I used a 3.25 lb Bausch & Lomb Advanced Titanium (essentially the same as a Slik 340DX with the short center column), Vanguard ABH 120K ballhead, and a Wimberley Sidekick with the lens mounted with the tripod ring from a Tamron SP 80-200 f2.8 Adaptall2. I probably could have done as well without the Sidekick. . .

I used my Tasco Red Dot Sight mounted on a Photosolve Xtend-a-Sight to spot the birds on the LCD, and this worked better than expected with the long FL EQ.

For context again, 47mm perspective (so as seen by bare eyes) taken from the same distance.



Here's one I picked to post a downsized original with no PP, the same shot PP'd to taste, and a 100% crop without any PP or downsizing.

Here's the unprocessed, downsized image


This is processed to taste with Denoise and InFocus -- really not much difference. . .


Here's the 100% crop, no downsizing or processing.


The rest are resized in steps only, no processing. As you can see from the sample above, none is really needed.













For me, this confirms what I had guessed would be the case with the Q, that premium SLR lenses would easily have enough resolution to produce high quality images if the Q's sensor did its part -- and IMO, the Q does very well.

Even with MF, these were pretty easy to shoot, and I still have yet to be adept at MF with the LCD. . . The Red Dot Sight makes it very easy to locate subjects, and focusing with this lens was easier than with the zooms because it's sharper with more contrast. I shot 104 frames, and only about 20 were unacceptably out of focus. Another 20 had unacceptable blur because of either subject motion or I moved the camera. This is really an unusually high percentage for me, but the birds were cooperating to some extent.

There's a bit less ultra-fine detail, compared to the best I can do with the K20. K-7, or K-5, but that level of detail is very difficult to achieve, and with the level of technique that I normally use, getting it is more luck than skill, even with a DSLR. I'd be very happy to consistently get this quality from any of my DSLRs.

In my experience, my FA* 300 f2.8 will do even better, but not by a whole lot. I probably won't get to really give it a try until Spring as it's just getting too cold for me. . .

In the meantime, I still have a bunch of lenses to try. . .and it should continue to be interesting -- stay tuned. . .

Scott

12-02-2011, 06:42 PM   #2
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Very nice pics, but if you ask me, the result is no better than cropping an APS-C photo as far as resolution goes because of the MF, diffraction, and reduced DOF.

Adam
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12-02-2011, 06:48 PM   #3
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Great post. Love how you are coaxing this out of the Q. Incredible job. Just got the JR lens adapter. with tripod mount. It is not too bad using the Pentax A*300 f4 lens. Hardest part is aiming it quickly. Thought about adding mechanical aiming device. Your red dot seems like an even better idea. Have to research it. What holds it on the camera?

It has been so dark in the midwest lately. Can barely get 1/100 at f4 and ISO 400. Need more light.
thanks
barondla
12-02-2011, 08:34 PM   #4
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QuoteOriginally posted by Adam Quote
Very nice pics, but if you ask me, the result is no better than cropping an APS-C photo as far as resolution goes because of the MF, diffraction, and reduced DOF.
Hi Adam,

On the surface, you are not incorrect -- for unprocessed images. Even with a 16 MP. APS-C, when cropped this much, the images become noticeably pixelated. and this really can't be corrected, while lack of sharpness can be helped considerably in post.

Personally, I'd rather have a somewhat soft 12MP image that can be worked with rather than a a 1.2MP file that's originally sharper at the pixel level for just about any output purpose, but you're certainly entitled to your opinion.

As far as DOF goes, the additional distance I can shoot at makes the DOF deeper, which is good for me. I have small bird portrait shots that have the head and body in focus, but the feet are not just soft, but blurred. That diminishes the shot in my eyes, though it does isolate the bird well with a busy background.

I've attached a 1368x912 crop from a K-5 image (an equivalent crop to the Q's frame). Unfortunately it had to be downsized slightly to 1024 on the long side to fit the attachment parameters, but that degree of downsizing doesn't have much effect on the character of the image). You can easily see the aliasing problems caused by the lower resolution, and the situations are few where this would yield close to equal final output. I could easily sharpen even the downsized unprocessed Q images to yield a considerably better final image than the K-5 crop.

Scott

Attached Images
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PENTAX K-5  Photo 

Last edited by snostorm; 12-02-2011 at 09:11 PM. Reason: additional comment
12-03-2011, 01:06 AM   #5
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Thanks again for giving an update, this time with the FA*300.
I must say, its pretty impressive and I think I'm pretty convinced to get myself a Q.


One question regarding AF with either std zoom or prime 01;
Can you roughly describe how fast is the AF? (or example as compared to K7; K5; or a m4/3; etc)
I would also like to use the Q for street photography and a rather quick and decisive AF would be preferred.
Thanks
12-03-2011, 11:21 AM   #6
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QuoteOriginally posted by pinholecam Quote
Thanks again for giving an update, this time with the FA*300.
I must say, its pretty impressive and I think I'm pretty convinced to get myself a Q.


One question regarding AF with either std zoom or prime 01;
Can you roughly describe how fast is the AF? (or example as compared to K7; K5; or a m4/3; etc)
I would also like to use the Q for street photography and a rather quick and decisive AF would be preferred.
Hi phc,

Thanks for taking a look.

The AF with the Q, after the FW update, is very quick and decisive in just about any outdoor daylight lighting conditions -- say down to + 8 to 9 Ev (heavy overcast). At Ev +4 to 5 it can struggle if there's not enough contrast in the AF area, and it sometimes will not lock focus. In speed, outdoors, it is considerably faster than the K-5 as the focusing throw is very short compared to an SLR lens.

I've not been much of a street shooter, but I'm looking to try my hand at this genre more with the Q. I've obtained a Leitz Brightline 50 accessory OVF, mainly for this purpose, and it looks like it will work well with some mental adaptation. The Q with the 01 prime shoots about a foot wider on each side than the frame lines of the BL 50 in landscape orientation, and about half that vertically at about 6 feet. The parallax correction frame line for close-in shooting works pretty well, and it's not hard for me to adapt. This OVF does not magnify, so I can easily shoot two-eyed, and the tightness of the VF does not really interfere as I can see outside the frame lines with the other eye and guesstimate the captured FOV pretty reasonably. The BL 50 is just slightly larger in diameter than a Nickel (@ 20mm) so it really doesn't make the camera much larger. I was able to find one for less than half of the cost of the Pentax OVF for the Q. A 40mm OVF might be a better option. . .

Here's a very good article on rangefinder OVFs that have been available:

Leica View Finders

I shot candids with the Q at Thanksgiving of some family and friends, and the camera almost went unnoticed. Everyone was surprised at how many pics I actually took of them, and this was a good sign for me as I tend to be a bit self conscious when shooting people. Using the LCD, at some odd angles and close to my face, though I couldn't see the image on the LCD well, but I could still frame the subject and see the green AF confirmation easily, and these shots also turned out well. I'm gaining a pretty high level of confidence in the accuracy of the AF system with the Q system lenses.

Scott
01-25-2012, 07:43 PM   #7
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@snostorm,

I read your tests with the FA*300/4.5 and DFA 100/2.8WR with interest.

However, I am worried that you didn't take one issue into account: diffraction.

Due to the small pixels, the Q is diffraction limited much sooner than an APSC SLR. According to photozone.de and surprisingly, the resolution figures (with aggresive enough sharpening!) remain high until and including f/4.0. That's good news as naive analysis would yield an even lower threshold. Sharpening is your friend here.

But the bad news is: Beyond f/4.0, e.g. f/5.6, resolution is really destroyed.

The FA*300/4.5 has no f/4.0 and its sweet spot is closer to f/5.6 anyway. So, a DA*300/4 may perform significantly better here. Or a FA*300/2.8.

And you really need to retest your DFA 100/2.8WR at a reasonable aperture, like f/4. Or better yet the DA 70 Ltd. as it has its sweet spot at f/4 rather than f/5.6. The DA 70 Ltd. used at f/4 should be able to exploit Q's full resolution.

@Adam, I disagree that cropped APSC can come close to the performance shown here. The Q's pixels are so small (1.5Ám) that even a 4x loss in resolution (3Ám) provides 3x the detail of a perfect!! APSC picture (5Ám). And perfect 300mm APSC pictures are a very rare beast...

If anything, a good 500mm with 1.7x TC would probably be a fair comparison to a DA*300 at f/4.5 on the Q.
01-26-2012, 05:47 AM   #8
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QuoteOriginally posted by falconeye Quote
Due to the small pixels, the Q is diffraction limited much sooner than an APSC SLR.
Surely you mean due to the small sensor?

Pixel pitch should not matter as even simple pixel binning can always simulate bigger pixels.

The real issue, as I see it, is the small sensor size (effective image circle). If one converts f/5.6 on the Q to an equivalent f-ratio on APS-C (f/21) or FF (f/31) it becomes obvious why respective images will suffer from diffraction-induced blur (irrespectively of pixel size).

01-26-2012, 07:25 AM   #9
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QuoteOriginally posted by Class A Quote
Surely you mean due to the small sensor?

Pixel pitch should not matter as even simple pixel binning can always simulate bigger pixels.
You are right in general, but in this instance I meant pixel pitch indeed.

We talked about a use case where -- whatever be the sensor size -- an image is cropped from the center at 100%. A larger sensor would grab a larger image, but the center wouldn't have more detail. Let's call this a comparison of "reach".

And for this comparison, we need to consider (among many other factors) the diffraction-limited distance two lines can be separated. For the Q (with its 1.5Ám pixels), it needs to be 3Ám or the F-stop needs to be f/4.5 (3Ám/1.22/0.55Ám). Beyond f/4.5, information at the Nyquist frequency is lost in a way it can't be recovered via sharpening or deconvolution. The photozone.de test of the Q prime lens shows this very dramatically. This limit depends on pixel pitch, not sensor size.

The problem is there aren't many lenses which are diffraction limited at f/4 already ... (the DA 70 Ltd. being my best candidate)

Another discussion are equivalent cameras where the total number of pixels is kept a constant, i.e., where pixel pitch scales with sensor size. But it is a different discussion indeed.
01-27-2012, 12:27 PM   #10
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Falk,

I've read this thread with interest but am a little at sea. I am not mathematically or scientifically challenged by any means, but don't have a solid background in the optics of digital capture. Is there a web resource you could point me to that could help explain the relationship of pixel pitch and diffraction limitation?

I'd be ever so grateful,

Bob
01-27-2012, 04:20 PM - 2 Likes   #11
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QuoteOriginally posted by bkpix Quote
Falk,

I've read this thread with interest but am a little at sea. I am not mathematically or scientifically challenged by any means, but don't have a solid background in the optics of digital capture. Is there a web resource you could point me to that could help explain the relationship of pixel pitch and diffraction limitation?

I'd be ever so grateful,

Bob
You can visit http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm which is an excellent resource on the topic.

I use what they call barely resolved to put the Q's diffraction limit at f/4.
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