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05-02-2014, 03:34 AM   #136
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QuoteOriginally posted by JimmyDranox Quote
That's not about the camera qualities. Is about how Ricoh present 645z, like a FF replacement. And in my opinion, if they think that is a good strategy, I think they are wrong. Because, many Pentax users who waits for an FF Pentax could be made to think that this camera will never come, and they will think to move to other system. And I'm pretty sure that the number of people who want a FF camera is much bigger that those who can afford a 645z. So, this Ricoh marketing strategy can backfire.

No, I'm wrong. This strategy has already backfired. And this thread is a proof.
I think people are way over reading the advertisement materials for the 645z. For whatever reason, Hoya decided to actually launch the digital medium format camera that had been under development for ages in 2010. I suppose they saw it as a low risk situation -- high margins, no new tech needed (as it shares a lot of features with APS-C cameras). Ricoh has clearly decided to continue to support the camera and continue its development and they see digital medium format as being a top end product that few others can match.

Even if Ricoh would bring out a full frame camera down the road, the 645z will still remain their top end camera, purely due to its sensor size and cost. But, honestly, most of the folks who are interested in full frame would not be particularly interested in medium format -- at least not at current prices.

05-02-2014, 06:31 PM   #137
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QuoteOriginally posted by Rondec Quote
I think people are way over reading the advertisement materials for the 645z. For whatever reason, Hoya decided to actually launch the digital medium format camera that had been under development for ages in 2010. I suppose they saw it as a low risk situation -- high margins, no new tech needed (as it shares a lot of features with APS-C cameras). Ricoh has clearly decided to continue to support the camera and continue its development and they see digital medium format as being a top end product that few others can match.

Even if Ricoh would bring out a full frame camera down the road, the 645z will still remain their top end camera, purely due to its sensor size and cost. But, honestly, most of the folks who are interested in full frame would not be particularly interested in medium format -- at least not at current prices.
Pentax was in a unique position. They were the only mainstream manufacturer who could come out with a digital MF camera for such a low investment (Even if Fuji could have, they essentially failed the first time in the digital ILC market, and had to completely re-enter it more recently to finally find success). So even under the cheap, Pentax-gutting "leadership" of Hoya the 645D made sense. Sony, Canon, Olympus, Panasonic, Sigma, and probably even Nikon would have to use someone else's lenses or start from scratch.
05-03-2014, 04:17 AM   #138
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QuoteOriginally posted by philbaum Quote
Falk noted that in the K3 PF Review, that larger format cameras have an innate advantage in focusing over a smaller format, i.e. you'd normally expect a FF to better AF than an APS camera, so it follows that the 645Z is likely better at AF than a FF or an APS camera. But, the Pentax K3 was built with -3ev focusing capability and fast processing, so i'd assume these better traits were also transmitted into the 645Z.
It is common sense. Larger sensor allows for larger DoF under the same AF point and same focal length. In case of the 35mm sensor, it means extra 50% leeway on top of K-3's abilities to obtain well focused photo. Thus even with the same AF system as in the K-3, a theoretical 35mm camera from Pentax will overnight become a "miracle", because even the sloppiest and blindest of users will get 50% more keepers.

And everyone will talk about "Pentax has vastly improved its AF for the 35mm camera" and other nonsense.

But indeed, if for nothing else than for that positive perception alone Pentax needs a 35mm camera. Even with half a dozen lenses it will be good enough to create positive halo effect. A modern 35mm DSLR will help sell more crop Pentax cameras, no doubt about it, and will justify and give new life to many technological improvements now implemented in the K-3.

Even if it has nothing extra special apart from new mirror and a sensor, and shares all other parts with K-3, a 35mm camera will be a true revelation and a huge experiential improvement to all K-mount users. Suddenly all technologies in the K-3 will come to more prominence and have more investment sense.

Now we know the technology migration path: K-3 —> 645Z —> further APS-C bodies —> 35mm. All share bulk of same tech, and only like that Pentax can achieve internal economy to make a 35mm camera as economically as possible.

Last edited by Uluru; 05-03-2014 at 04:32 AM.
05-04-2014, 12:35 AM   #139
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QuoteOriginally posted by philbaum Quote
Falk noted that in the K3 PF Review, that larger format cameras have an innate advantage in focusing over a smaller format, i.e. you'd normally expect a FF to better AF than an APS camera, so it follows that the 645Z is likely better at AF than a FF or an APS camera.
QuoteOriginally posted by Uluru Quote
It is common sense. Larger sensor allows for larger DoF under the same AF point and same focal length. In case of the 35mm sensor, it means extra 50% leeway on top of K-3's abilities to obtain well focused photo. Thus even with the same AF system as in the K-3, a theoretical 35mm camera from Pentax will overnight become a "miracle", because even the sloppiest and blindest of users will get 50% more keepers.

And everyone will talk about "Pentax has vastly improved its AF for the 35mm camera" and other nonsense.

Can you both please explain this? And can you show me exactly where Falk said this, because I can't find it anywhere in the review.

This isn't making any sense to me.


At the same FOV and aperture the DOF is less as the sensor gets larger (although, of course, truly optimum focus is still only found within a smaller section of what's considered the "in-focus" area which defines the DOF).


There are many aspects of AF performance (for example focus speed, accuracy, precision, AF points (number, size, area, precision of each point), and on and on). I don't even know what aspects you're referring to here.

05-04-2014, 04:04 AM   #140
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Bigger formats is slower to focus than smaller ones all things equal. Firstly DOF is larger on the smaller format giving more leeway for errors (if the format is small enough AF is as fast as the speed of light; ie fixed focus!), hence the AF doesn't need to be that precise (all AF systems give ballpark figure for correct focus. Smaller formats just have a larger ballpark). Secondly, larger formats have generally larger lenses and always lenses with longer focus throw than smaller formats for the same angle of view. This means more physical work for focusing. Add the fact that larger formats are usualy used in order to be able to print larger appealing to a more critical crowd; hence focus is more critical.
The AF algoritms are different on different format cameras even if they use the same AF system (eg Pentax). They are tuned towards more preciscion in larger formats (for the reasons above) which translate into slower speed all else equal.

Last edited by Pål Jensen; 05-04-2014 at 04:17 AM.
05-04-2014, 05:25 AM   #141
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QuoteOriginally posted by DSims Quote
Can you both please explain this?
i can. Just read precisely what i quote and you'll get the answer.

QuoteOriginally posted by DSims Quote
Larger sensor allows for larger DoF under the same AF point and same focal length
then you said

QuoteOriginally posted by DSims Quote
At the same FOV
Here, lies the mistakes : the same focal lenght will be wider on FF than APS-C when it comes to FoV, and then the DoF will be bigger in FF than APS-C.

A 35mm on FF gives a wider FoV than on APS-C.

Hence, 35mm on FF gives more DoF than on FF.

Hence, Focusing is easier on FF than APS-C WHEN THE FOCAL LENGHT REMAINS THE SAME.


Tadaa ! mystery solved.
05-04-2014, 05:48 AM   #142
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This can be checked very easily with a depth of field calculator.

For an instance, a Nikon APS-C, with a 50mm lens, at f1.4, at 1 meter distance, will have a DOF of 0.02 meter. A Nikon FF, with the same lens, aperture, distance, will have a DOF of 0.03 meter.

http://www.dofmaster.com/dofjs.html
05-04-2014, 06:22 AM   #143
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QuoteOriginally posted by JimmyDranox Quote
This can be checked very easily with a depth of field calculator.

For an instance, a Nikon APS-C, with a 50mm lens, at f1.4, at 1 meter distance, will have a DOF of 0.02 meter. A Nikon FF, with the same lens, aperture, distance, will have a DOF of 0.03 meter.

Online Depth of Field Calculator
Now check it with a camera, and you might understand why I recommend people ignore DoF tables. If you're using Nikon, take the lens off your D800 and put it on your D7000, that's approximately the same pixel pitch. Now shoot with the D800 in DX mode or measure your DoF in the middle of the frame, you should have the same DoF, no matter what the DoF calculator says.

Now shoot with a 35mm lens from the same position to maintain your field of view on APS-c, you'll have twice as much DoF with the APS-c camera, I've tested this myself, and done the measurements. If you don't understand why this is true, you don't understand how to use the calculator. There's nothing wrong with the math, what's wrong is the way it's applied.

As I have repeatedly said, with enough caveats the DoF calculator might work, without an explanation of the precise caveats and correct interpretation, it's more likely to create confusion than understanding.

Honest to Pete, if you're going to use science to make claims, test your results empirically. It's the only way to make sure you understand the theory correctly.


Last edited by Ash; 05-04-2014 at 01:52 PM.
05-04-2014, 07:33 AM   #144
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It all depends on what is changing and what remains constant. In JimmyDranox's scenario, everything is constant but enlargement: indeed, APS-C is just cropping (and enlargement to the same print size) of the "full frame" image; and the DOF will of course decrease. The smaller format who will be enlarged more has a smaller circle of confusion.
You are finding the same DOF in the first paragraph because you're not considering enlargement/CoC.

Last edited by Kunzite; 05-04-2014 at 11:51 PM.
05-04-2014, 01:23 PM   #145
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QuoteOriginally posted by Uluru Quote
Larger sensor allows for larger DoF under the same AF point and same focal length.
*Smaller* DoF, and less keepers by the logic in your paragraph, Uluru.
05-04-2014, 04:48 PM   #146
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Ok, no graphs. First off, I'll confess to not contributing to the forums. I do read them, so I should thank everyone who contributes. Thanks!

I'd buy a ff Pentax if it came out, but I see advantages to the aps-c. The 50mm FA 1.4, for example, becomes a great portrait lens, which even holds together in video. But the point I want to make is that a vintage k mount lens (the 50 FA was first manufactured in 1991) can give you an insanely shallow depth of field. If you're willing to go to the A or the M lenses, you have an incredible array of lenses that go back to the 70s. If you want to have all the functionality of your K3, or whatever, stick to the F or FA series. Keep your aperture open and you can get as shallow as you want.

I'd buy an ff pentax for the low light and the wide angles (which to my eye are really hard to get looking good in aps-c), and most importantly, the image quality. Given the way pentax has pushed the aps-c, I'd be feeling good about pentax pushing a ff sensor. Furthermore, I'd rather switch over now. With mirrorless full frame cameras, and Pentax itself going after the mf market, it seems inevitable that the current aps-c market niche is fated to become a full frame niche. Yes, even better control of DOF, but more important: out of control stills, 2k or better video, and fantastic lenses at a fraction of the cost of the competition.
05-04-2014, 05:21 PM   #147
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QuoteOriginally posted by clackers Quote
*Smaller* DoF, and less keepers by the logic in your paragraph, Uluru.
From the DOF master website:
Camera: Canon 7D (APS-C)
Focal length: 55
F stop: 2
Subject distance 10 ft
DoF Total: 0.75ft

Camera: Leica M9 (35mm)
Focal length: 55
F stop: 2
Subject distance 10 ft
DoF Total: 1.19ft (or 1.58x more than 7D DoF)

Practically, it is easier to use factor 1.5, which practically means 50% more DoF for the 35mm camera.
It is a fact, not a common misconception spread around Internet that “FF cameras allow for “shallow” DoF”. That popular statement is wrong as long as “shallow” means “less depth” in English dictionary. 35mm cameras allow for more, not less DoF using same lens and f stop. But what also matters in image characteristics is the transition between DoF and OoF areas, or, the “isolation” of the DoF area. That is why (I presume) DoF described as "shallow", but wrongly: in fact it is the OoF area that appears "compressed" or more "undefined".

It would be best to say: Compared to crop cameras, 35mm cameras allow for more DoF, therefore more focusing leeway, and shallower look of the OoF.

That is why it is unfair and wrong to compare precision of the AF system in Pentax crop cameras to Nikon's digital 35mm cameras. PF did that some time ago in their tests to mark Pentax's AF system unfavourably, as Nikon's 35mm digital camera yielded more keepers. Goodness gracious, of course it does! But how would Pentax's 35mm digital camera compare? No one knows, and that is why Pentax is bashed around for its "poor" AF in such unfair and wrong comparisons.

It is the similar level of misconception as the Geocentric worldview. Although Sun in the sky "appears to move" from horizon to horizon, in fact the Earth rotates and creates that illusion.

Last edited by Uluru; 05-04-2014 at 08:23 PM.
05-04-2014, 06:16 PM   #148
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QuoteOriginally posted by Uluru Quote
From the DOF master website:
Camera: Canon 7D (APS-C)
Focal length: 55
F stop: 2
Subject distance 10 ft
DoF Total: 0.75ft

Camera: Leica M9 (35mm)
Focal length: 55
F stop: 2
Subject distance 10 ft
DoF Total: 1.19ft (or 1.58x more than 7D DoF)

That is 50% more DoF for the 35mm camera.
That is a fact, not a common misconception spread around Internet that “FF cameras allow for “shallow” DoF”. That popular statement is entirely wrong as long as “shallow” means “less depth” in English dictionary. 35mm cameras therefore allow for more, not less DoF using same lens and f stop. But what also matters is the transition between DoF and OoF areas, or, the “isolation” of the DoF area. That is why DoF is described as "shallow", but wrongly: in fact it is only the OoF area that appears "compressed" or more "undefined".

Or it would be best to say: Compared to crop cameras, 35mm cameras allow for more DoF, therefore more focusing leeway, and shallower look of the OoF.

That is also why it is unfair and utterly wrong to compare precision of AF systems in Pentax crop cameras to Nikon's digital 35mm cameras. That is what PF did some time ago in their tests to mark Pentax's AF system unfavourably as Nikon's 35mm digital camera yielded more keepers. Goodness gracious, of course it does. But how would Pentax's 35mm digital camera compare? No one knows, and that is why Pentax is bashed around for its "poor" AF in such unfair and wrong comparisons.

It is the similar level of misconception as the Geocentric worldview. Although the Sun "appears to move" from horizon to horizon, in fact the Earth rotates and creates that illusion.

Like your explanation, Uluru ... you've convinced me.


Essentially, teles give you less DoF, and a lens on cropped factor becomes 50% more tele.


But I wonder if an 'authority' like Steve Huff will agree? .... Just for fun: Sensor Sizes compared for depth of field – Small, Medium and Large! | STEVE HUFF PHOTOS

Last edited by clackers; 05-04-2014 at 06:27 PM.
05-04-2014, 07:33 PM   #149
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QuoteOriginally posted by Uluru Quote
From the DOF master website:
Camera: Canon 7D (APS-C)
Focal length: 55
F stop: 2
Subject distance 10 ft
DoF Total: 0.75ft

Camera: Leica M9 (35mm)
Focal length: 55
F stop: 2
Subject distance 10 ft
DoF Total: 1.19ft (or 1.58x more than 7D DoF)

That is 50% more DoF for the 35mm camera.
That is a fact, not a common misconception spread around Internet that “FF cameras allow for “shallow” DoF”.
Are there people here who didn't understand the above? There should be no confusion about using the same lens on two formats, right?

In that example, you're getting a radically different picture, with the aps-c shot cropped 1.5x times. If you keep the FOV the same, distance to subject the same, and the F-stop the same, you get less DOF with the FF shot (and more DOF 'control' at the higher apertures.)

This describes what photographers do more closely - they don;t switch formats and then accept radically different framing from there on out, the rest of their shooting career They use a different FL to get the same 'stuff' in the frame they always did. If you zoomed to 35mm before, you zoom to 52mm now, on FF. If you were shooting 16mm on aps-c, you use 24mm on FF, etc, etc.

.
QuoteQuote:
That popular statement is entirely wrong as long as “shallow” means “less depth” in English dictionary. 35mm cameras therefore allow for more, not less DoF using same lens and f stop.
Which people rarely do - or, they do use the same lens, but for different framing applications.

QuoteQuote:
Or it would be best to say: Compared to crop cameras, 35mm cameras allow for more DoF, therefore more focusing leeway, and shallower look of the OoF.
I think you're having the increased AF accuracy being dependent on 'using the same lens on both formats', and it doesn't depend on that. It also doesn't really depend on DOF at all a lot of the time, the difference probably usually comes from the aps-c image being magnified 1.5x, showing the focusing errors more clearly, or as Falk talks about the PDAF detectors are likely to work more accurately with FF assuming the same PDAF tech.

.
05-04-2014, 07:37 PM   #150
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QuoteOriginally posted by Uluru Quote
From the DOF master website:
Camera: Canon 7D (APS-C)
Focal length: 55
F stop: 2
Subject distance 10 ft
DoF Total: 0.75ft

Camera: Leica M9 (35mm)
Focal length: 55
F stop: 2
Subject distance 10 ft
DoF Total: 1.19ft (or 1.58x more than 7D DoF)

That is 50% more DoF for the 35mm camera.
That is a fact, not a common misconception spread around Internet that “FF cameras allow for “shallow” DoF”. That popular statement is entirely wrong as long as “shallow” means “less depth” in English dictionary. 35mm cameras therefore allow for more, not less DoF using same lens and f stop. But what also matters is the transition between DoF and OoF areas, or, the “isolation” of the DoF area. That is why DoF is described as "shallow", but wrongly: in fact it is only the OoF area that appears "compressed" or more "undefined".

Or it would be best to say: Compared to crop cameras, 35mm cameras allow for more DoF, therefore more focusing leeway, and shallower look of the OoF.

That is also why it is unfair and utterly wrong to compare precision of AF systems in Pentax crop cameras to Nikon's digital 35mm cameras. That is what PF did some time ago in their tests to mark Pentax's AF system unfavourably as Nikon's 35mm digital camera yielded more keepers. Goodness gracious, of course it does. But how would Pentax's 35mm digital camera compare? No one knows, and that is why Pentax is bashed around for its "poor" AF in such unfair and wrong comparisons.

It is the similar level of misconception as the Geocentric worldview. Although the Sun "appears to move" from horizon to horizon, in fact the Earth rotates and creates that illusion.

Sorry, but you seem to have a fundamental misunderstanding of how to go about DOF calculations. Ether you or someone you have read is trying to reinvent the wheel, and not making a very good job of it.

In order to make a valid comparison between formats, you must take in to account the field of view of the lenses. For example, if you are using a 50mm on FF, the focal length for APS-C should be about 35 mm, not 50 mm. If you use the same field of view in both formats, same-size prints made from each format will show greater DOF in the APS-C images than the FF.

I'm not sure how you arrived at your calculation method. If you do some research in well-informed sources, such as books rather than on-line forums, you will find universal agreement that the larger the format, the less depth of field when field of view remains constant. That's a fact, confirmed by thousands upon thousands of expert photographers over many decades. And by me, having worked with a wide variety of formats professionally for over 30 years- including digital FF and APS-C.

Normhead and kunzite and jsherman999 are right.

To emphasize my point, APS-C offers greater depth of field than FF under the following conditions:

1. Same lens aperture used in both formats.

2. Same field of view used in both formats.

Getting back to the original point of this thread, I expect Ricoh/Pentax to produce a FF body this year or next. I view the introduction of the 645Z as an indication that Ricoh intends to take an aggressive stance in producing very competitive products at several levels. It would not surprise me if the corporate strategy is to take on Nikon and Canon head-to-head over the next decade. In that context, a FF appears inevitable. I have no idea whether such a strategy might work, as Pentax/Ricoh will have to greatly improve its service and support for professionals to become successful in that realm.
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