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04-03-2013, 09:49 AM   #31
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QuoteOriginally posted by pinholecam Quote
#1 - only possible at close focusing distances and far backgrounds. The Q is not intended for this purpose (Period)
It is possible to get very narrow depth of field with the Q, but you have to choose the right lenses. Fujinon currently makes some c mount machine vision lenses that will allow you to focus on an extremely narrow range just inches from the lens to 15 feet away. Old fast cine lens also offer the possibility of very nice bokeh with distances of ~ 2 -15 feet.

Sensor size is not the most important factor for bokeh.


Last edited by verdigris; 04-03-2013 at 09:55 AM.
04-03-2013, 01:58 PM   #32
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I pretty much thought I would be blowing off bokeh or serious portrait work on the Q. This was probably because of all the folks who were claiming that the DoF difference between FF and APS-c was so huge (in fact, having shot a lot of FF digital I knew the roughly one-stop difference isn't a real factor) - still this created an incorrect assumption about going to a super-small sensor yielding virtual pinhole effect.

Sure, you have to work at it quite a bit more, and you need to have lenses geared toward good bokeh in the first place. One of the better options is the Samyang/Rokinon 85mm:
Q miscellany - James Robins - Powered by Phanfare

I'm finding that very good zooms can carry over to decently sharp images with the Q, but they still often have bokeh issues at least for part of their range. Primes tend to bring out a more natural look on the Q. I have been surprised that bad bokeh (not just exaggerated CA) is a bigger overall issue than other challenges in adapted lenses.
04-03-2013, 06:06 PM   #33
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The problem is not the sensor, is the multiplier x5,6. There are hundreds of 50mm 1.4 very cheap, but in the Q are a 275mm ƒ8! It's way too long for portraits in general, need to be far away from the subject.

There is a very interesting lens, but it is also very expensive ($600): the Sonnetar 25mm 1.1! It is ideal for portraits, equivalent to a 137mm ƒ6. And have the Q mount, no need to buy chinese adapters!
04-03-2013, 07:05 PM   #34
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QuoteOriginally posted by ElvisQ Quote
The problem is not the sensor, is the multiplier x5,6. There are hundreds of 50mm 1.4 very cheap, but in the Q are a 275mm ƒ8! It's way too long for portraits in general, need to be far away from the subject.

There is a very interesting lens, but it is also very expensive ($600): the Sonnetar 25mm 1.1! It is ideal for portraits, equivalent to a 137mm ƒ6. And have the Q mount, no need to buy chinese adapters!
Take care in computing the f-stop as equivalent to the crop factor regarding most aspects of the image other than actual amount of light gathered. It does not work that way for most calculations, including DoF and bokeh characteristics. In fact, the shot linked above is an 85mm at f/2 and the DoF is the same whether the light falls of a FF, APS-c or the Q assuming no change in camera to subject distance.

Lenses faster than f/2 result in significant decline in sensor light acceptance. Very little light gets accepted beyond f/1.4, so the light gathering benefit becomes nearly inconsequential. I am yet to see an acceptable quality image captured on a digital shot at anything faster than f/1.4 (even if the sensor could accept most of the additional light provided).


Last edited by ScooterMaxi Jim; 04-03-2013 at 07:24 PM. Reason: Additional info regarding fast lenses
04-03-2013, 07:27 PM   #35
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QuoteOriginally posted by ScooterMaxi Jim Quote
It does not work that way for most calculations, including DoF and bokeh characteristics. In fact, the shot linked above is an 85mm at f/2 and the DoF is the same whether the light falls of a FF, APS-c or the Q.
Note that in my above reply I was referring to the Q01 Prime (8.5mm f/1.9) at various focus distances, not an 85mm f/2 lens, but according to DoFMaster iPhone app your assertion isn't perfect. It is pretty close, except Total DoF and hyperfocal distance. I was illustrating how hard it is to get a one or two foot Total Focus Distance to achieve some subject isolation with an 8.5mm lens on a Compact Digital sensor. Clearly with a traditional portrait lens (85mm @f2) that can be done at 20 feet on larger sensors, but CD? I wouldn't call 5" usable DoF.
  • Format - Compact digital
  • Lens - 85mm
  • f/stop - f/2
  • Focus distance
    • 20 feet
      • Near limit - 19.8 feet
      • Far limit - 20.2 feet
      • Total DOF - 0.4 feet
      • Hyperfocal distance 1975.6 feet
  • Format - APSc
  • Lens - 85mm
  • f/stop - f/2
  • Focus distance
    • 20 feet
      • Near limit - 19.4 feet
      • Far limit - 20.7 feet
      • Total DOF - 1.33 feet
      • Hyperfocal distance 592.9 feet
  • Format - 35mm
  • Lens - 85mm
  • f/stop - f/2
  • Focus distance
    • 20 feet
      • Near limit - 19 feet
      • Far limit - 21.1 feet
      • Total DOF - 2 feet
      • Hyperfocal distance 395.3 feet

Last edited by monochrome; 04-04-2013 at 08:39 AM.
04-03-2013, 07:41 PM   #36
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Monochrome is right
ƒ2.8 lets in the same amount of light in a fullframe than a Q, but for bokeh the aperture is multiplied by x5,6. So Q defocus lenses so little, even using the 06 to 45mm, because it's actually a 200mm ƒ16 for bokeh.
04-04-2013, 01:19 AM   #37
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QuoteOriginally posted by ElvisQ Quote
Monochrome is right
â2.8 lets in the same amount of light in a fullframe than a Q, but for bokeh the aperture is multiplied by x5,6. So Q defocus lenses so little, even using the 06 to 45mm, because it's actually a 200mm â16 for bokeh.
Bokeh can not be multiplied since it isn't a value, DOF can though
With the short register they should be able to make very fast lenses for the Q 9mm f/0.5 would be nice to have, finally use for the ND filter.
04-04-2013, 02:03 AM   #38
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Back to the OP. The Q may do a decent job for facebook and web images in well lit areas. Wouldn't like to have to up the iSO in a dark church, or present Bride and Groom with any prints bigger than A4.

If you're set on this come back and let us know how it all went.

04-04-2013, 02:17 AM   #39
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QuoteOriginally posted by Blythman Quote
Back to the OP. The Q may do a decent job for facebook and web images in well lit areas. Wouldn't like to have to up the iSO in a dark church, or present Bride and Groom with any prints bigger than A4.

If you're set on this come back and let us know how it all went.
Well that's the thing, i can understand that Pentax want to keep the price low and fun but for serious work 3 very good primes with large aperture would go a long way.

Canon made a 8.5–25.5 mm f/1.0 lens for Super 8, how perfect would that not be on the Q

Has anyone tried Super 8 Lenses on the Q btw?


C mount seems to work fine.
This looks like a good lens from Pentax for the Q.
http://www.bhphotovideo.com/c/product/341297-REG/Pentax_C60812_C60812_8mm_to_48mm.html

Last edited by Anvh; 04-04-2013 at 02:29 AM.
04-04-2013, 04:05 AM   #40
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QuoteOriginally posted by ScooterMaxi Jim Quote
Take care in computing the f-stop as equivalent to the crop factor regarding most aspects of the image other than actual amount of light gathered. It does not work that way for most calculations, including DoF and bokeh characteristics. In fact, the shot linked above is an 85mm at f/2 and the DoF is the same whether the light falls of a FF, APS-c or the Q assuming no change in camera to subject distance.
But there will be a change in camera to subject distance. (Also, the DOF is shorter the more you enlarge, so it's not the same between sensors in your model either.)

The simple calculations aren't perfect, certainly, but calling 85/2 equivalent to 475/2 is a lot more wrong than calling it equivalent to 475/11.
04-04-2013, 08:08 AM   #41
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Again, I was referring to a constant distance to subject, and focal length of a lens is always constant so 85mm is 85mm - period. The sensor is only limiting the FoV and not in any way altering the lens function. The point about amount of light gathered is a function of sensor size and not a change in the light falling on the sensor (although the center of the sensor does indeed always gather more light even with a "perfect" lens in theory as it is closer to the source).

My other point is far more important regarding lens choice and design. No reasonable lens maker should build a lens for current digital photo sensor use faster than f/1.4 (or even that fast is something of a reach in my experience) because the advantage in light gathering is negligible at best; and that doesn't even touch on the IQ blooming problem. It is an entirely different situation than film. For those perhaps not aware, see:

DxOMark - F-stop blues
04-04-2013, 09:13 AM   #42
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QuoteOriginally posted by ScooterMaxi Jim Quote
Thanks, was an interesting read.

I like to point out though that there is no camera like the Q in the list, there are all DSLR.
Would be interesting to see how it effect those.

Also there is still a gain.
04-04-2013, 10:01 AM   #43
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I agree - it would be interesting to know. Actually, it would be easier to test because the body does not know the aperture - and so there is no way for the ISO to be rigged to deceive the user (and no confirmed evidence that Pentax does this in the same way Nikon and Canon obviously do).

One reasonable theory, though, is that the problem is greater on the smaller sensors because the trend line does correlate to worse drop off as pixel pitch is reduced. Perhaps backside illumination (BSI) somewhat limits the problem, but that's offered as speculation (based on the idea that removal of circuitry along the light path can only be a good thing).
04-05-2013, 01:26 PM   #44
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I don't know if I can agree entirely with the idea that lens faster than 1.4 have no benefit. I can understand that there is a limit on light gathering ability for smaller sensors, but it seems in my experience that probably only happens in situation with abundant light. I shoot a lot at night with no flash, and the light gathering abilities of fast lenses are certainly useful in that respect. 17 mm f 1.4 or 1.5 C mounts do make nice portrait lenses with the Q.

It's never going to be a go to camera for weddings or advertising/fashion shoots, or national geographic, it's just not the most appropriate tool for those situations, but you're not limited to wide DoF if you don't want to be.

It's an extremely creative camera that you can have with you at all times.

Last edited by verdigris; 04-05-2013 at 01:50 PM.
04-05-2013, 04:04 PM   #45
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It would be interesting to have additional scientific explanation of the phenomena. What is quite clear, though, is that neither light intensity nor size of sensor is a driving factor.

Oblique angles of light is the main culprit. This was never a problem for film - as emulsion is essentially flat and very capable of accepting light from severe angles. My understanding is that pixels are not flat, and need to have the light hit more directly. I assume this is the reason why many lenses that work well on film (for instance some DA lenses on FF film bodies), have severe light fall off issues on digital. The measurements of light loss beyond f/1.4 are pretty significant, at more than half light loss. Some sensors in the test show a full stop of light loss.

I suppose if you like the soft watercolor look that comes with photos taken at f/1.4 or greater on digital sensors - or you just want to say you have a lens faster than f/1.4 - then there is no rational argument against that. I have some very nice f/1.4 lenses, but with modern sensors that do not greatly degrade when you push them an extra stop of ISO - I almost never shoot them wide open because I'm after the best-possible image quality. Only if I am going after a dreamy effect would I consider it - a toy look essentially.

Clearly the camera makers have come to the same conclusion. It isn't as though they didn't commonly build quality, fast primes in the film era, and sell them at reasonable prices. Fast lenses shot wide open produced fairly good images on film cameras - back in the day when 400 ASA (ISO) was considered super-fast. On digital in the modern age, it really isn't attractive - or necessary.
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