The "reach" of the Q - images

reh321 · 03-14-2016, 07:09 AM

Originally posted by pearsaab

the wood ducks are back in my pond so got chance to get some with the Q, Q-k adapter always use setting 1 or less (I have found going higher does not improve the picture quality). Sigma 500mm 4.5. i either use a remote or the 2 second delay to minimize my movement

Would movement actually make a difference since you are already losing some detail by shooting through a screen?

**barondla** · 03-14-2016, 09:33 AM

Nice images pearsaab. The feather detail is superb. That is quite a distance to shoot. I would find that very difficult without a red dot scope. Impressive.
Thanks for sharing
barondla

---------- Post added 03-14-2016 at 11:41 AM ----------

reh321, the losses would combine. Whatever loss there is shooting through glass or screen, is different than sharpness loss due to movement. Notice pearsaab is using a nice, hefty tripod. It all adds up. The Q and ultra telephoto photography can be very demanding.
Thanks
barondla

reh321 · 03-14-2016, 10:02 AM

Originally posted by reh321

Would movement actually make a difference since you are already losing some detail by shooting through a screen?

Originally posted by barondla

The Q and ultra telephoto photography can be very demanding.

Yes, I have experiential knowledge of that.
https://www.pentaxforums.com/forums/136-pentax-q/284804-baby-steps-3.html
{one of the questions I've been asking lately is whether the leaf shutter in the Pentax adapter provides a boost in sharpness}

When I started I was inside our den, shooting through glass, and eventually I moved out to our {cold and snowy} deck to eliminate that hindrance to sharpness;
I've been doing what I can to optimize each component that affects sharpness, within the limits set by my budget
I stated my question poorly, but I asked it because I thought the screen might do more harm to sharpness than the tripod did good.

**pearsaab** · 03-14-2016, 01:46 PM

Originally posted by reh321

Yes, I have experiential knowledge of that.
https://www.pentaxforums.com/forums/136-pentax-q/284804-baby-steps-3.html
{one of the questions I've been asking lately is whether the leaf shutter in the Pentax adapter provides a boost in sharpness}

When I started I was inside our den, shooting through glass, and eventually I moved out to our {cold and snowy} deck to eliminate that hindrance to sharpness;
I've been doing what I can to optimize each component that affects sharpness, within the limits set by my budget
I stated my question poorly, but I asked it because I thought the screen might do more harm to sharpness than the tripod did good.

I actually have the window open and yes i have tried shooting through glass and you will definitely lose sharpness. Movement will impact the picture as well. As long as they stay in the approximate area then when i have the 2 second delay or the remote i can catch them some of the time. If they are moving fast there is no way to keep up with them especially with low shutter speeds. You must have a stable platform or you will not stand a chance to get the picture. I have never used anything but the qk adapter so don't know how critical that is.

**barondla** · 03-14-2016, 01:56 PM

reh321, sorry, I see what you were asking now. Trade offs of shooting thru the screen and not using a tripod.I would say shooting through screen is better than doing without a tripod. Especially with a 500mm lens that weighs that much. Doubt anyone can shoot that combo reliably hand held.

To answer your adapter question. I started with a generic. First one that came out. Recommended by snowstorm. it was horrible, but all that was available. The tripod foot broke holding a 100mm lens. The insides of the adapter were bright and shiny. Took the phono cartridge size screws and put big nuts on them. Then JB Weleded it together. Painted the inside with flat black paint. Great image improvement. Later a poster recommended black felt flocking instead of paint. That helped. More contrasty images.

Then Pentax brought out their Q>PK adapter with leaf shutter. On still subjects using a tripod the sharpness between generic and Pentax are close. Pentax wins slightly, very slightly. Figure this comes down to better internal flare reduction because Pentax uses felt flocking, groves in the metal, and aperture plates. Hard to beat that. The massively stable tripod foot could also play into it.

With moving subjects the Pentax adapter is considerably sharper. This also holds true for hand holding a 100 - 300mm lens. Sensor shutter has serious motion artifacts. No matter the shutter speed the sensor scans one line at a time. Take a desk fan, put it outside in bright sun pick 1/1000 or higher shutter speed. Turn fan on and photograph the fan face. It won't look like fan blades. Kind of like bizarro Superman.

Hope this helps.
barondla

**barondla** · 03-14-2016, 03:10 PM - **1 Like**

reh321, these tips were posted about a year ago in another thread.

How I shoot with the original Q.

1. Use the sturdiest tripod you have.
2.Turn off SR.
3. Use wireless remote.
4. Red dot scope to speed up subject location.

5. Lowest ISO you can get away with.
6. Shoot Raw.
7. LCD set to maximum brightness.
8. LCD magnification set to 4x.
9. Auto bracketing on and set to +- .3 allows Q to shoot 3 shot burst pictures faster.
10. Plenty of extra batteries. They will be needed.

If it is a fairly static subject not doing anything super special, I live with slower shutter speeds. May have to shoot a lot to
get one without motion blur . Can live with that. If subject is doing someting special , higher ISO will capture it.

Always use a wireless remote. Wish the Q wasn't as finicky with the rear sensor. Being mirrorless is a blessing with ultra telephoto shooting.

This is how I shoot others may have their special techniques. Patience and practice are very helpful.

Read more at: https://www.pentaxforums.com/forums/136-pentax-q/284585-extreme-telephoto-tip...#ixzz42ux7q8Of

**Weevil** · 03-22-2016, 10:45 PM - **1 Like**

(xposted on the HDTC thread)
Been shooting waterfowls this weekend, and had a chance to test the Q7 on my FA*250-600 + HDTC 1.4x, and after reviewing all your good advises, I was able to get some interesting results...

The 2 next Photos taken with Pentax K-3 + FA*250-600 @ 600mm.
The 1.5x crop factor gives a 900mm FF equivalent.

photos are the original size (not cropped) from the K-3.

Bernache nonnette / Barnacle Goose [Branta leucopsis] by Sylvain Cote, sur Flickr

Bernache nonnette / Barnacle Goose [Branta leucopsis] by Sylvain Cote, sur Flickr

Photo taken with Pentax K-3 + HDTC 1.4x + FA*250-600 @ 600mm (840mm).
The 1.5x crop factor of the K-3 gives a 1260mm FF equivalent.

This photo is the original size (not cropped) from the K-3.

Bernache nonnette / Barnacle Goose [Branta leucopsis] by Sylvain Cote, sur Flickr

Photo taken with Pentax Q7 + Q-K Adapter on FA*250-600 + HDTC 1.4x.
The Lens + HDTC1.4x = 840mm (1260mm equivalent on a APS-C sensor), combined with the 4.59x crop factor of the Q7 sensor (Sensor size is 1/1.7" or 7.44 x 5.58 mm), that gives a total of 840mm x 4.59 = 3856mm !!!
I dont have to tell you that I am using a very sturdy tripod, and a IR remote shutter release to minimize the vibrations.

This photo is the original size (not cropped) from the Q7.

Bernache nonnette / Barnacle Goose [Branta leucopsis] by Sylvain Cote, sur Flickr

However, do I get more details if I crop the 24mp image from the K-3 + HDTC ? not sure...

this is an example of a crop image taken with the K-3 + HDTC + FA-250-600

Bernache nonnette / Barnacle Goose [Branta leucopsis] by Sylvain Cote, sur Flickr

a bit less crop here..

Bernache nonnette / Barnacle Goose [Branta leucopsis] by Sylvain Cote, sur Flickr

**barondla** · 03-24-2016, 09:42 PM

Weevil, nice images! Usually the Q7 will beat cropping a K camera. I would try using the 250-600 by itself, without the 1.4 converter. Your lens is already f5.6 at 600mm. Adding 1.4 HDTC means effectively it is f8. That is closing down pretty far with the Q7 and diffraction starts robbing sharpness.

I shoot the original Q with Pentax A*300 and almost always stop down 1 stop to f5.6. The lens is sharper 1 stop down. Imagine your lens would also be sharper 1 stop down, especially with the 1.4 teleconverter. Unfortunately, that puts you at f11 and the diffraction probably hampers sharpness considerably. Try without converter.
Thanks
barondla

**pacerr** · 03-24-2016, 10:53 PM

Originally posted by barondla

Adding 1.4 HDTC means effectively it is f8. That is closing down pretty far with the Q7 and diffraction starts robbing sharpness.

;
Yes, but . . . have you actually "closed down" the size of the aperture? Diffraction is a function of the physical 'size' of the aperture, no? As the aperture is closed down the proportional difference between the total AREA of the 'hole' and the diffraction-producing circumference of the rim of the hole changes. Radius-squared vs. (radius x 2) X 3.14 (pi).

The one-to-two stop EV loss with a TC is a function of the total light lost to the sensor (cropped image spill over and additional glass) rather than a physical change to the size of the lens aperture itself. While it does affect exposure I don't believe it affects the parameters for diffraction.

I may be wrong about that but it's been my understanding of the situation. Sensor and pixel size are another issue.

vonBaloney · 03-25-2016, 06:28 AM

Originally posted by pacerr

;
Yes, but . . . have you actually "closed down" the size of the aperture? Diffraction is a function of the physical 'size' of the aperture, no? As the aperture is closed down the proportional difference between the total AREA of the 'hole' and the diffraction-producing circumference of the rim of the hole changes. Radius-squared vs. (radius x 2) X 3.14 (pi).

The one-to-two stop EV loss with a TC is a function of the total light lost to the sensor (cropped image spill over and additional glass) rather than a physical change to the size of the lens aperture itself. While it does affect exposure I don't believe it affects the parameters for diffraction.

I believe it is the effective aperture that counts, i.e. even extension tubes or bellows with no optical elements can affect diffraction. Here's a debate about it:

https://www.pentaxforums.com/forums/136-pentax-q/185307-do-teleconverters-cou...-equation.html

**Weevil** · 03-25-2016, 06:33 AM

Originally posted by barondla

Weevil, nice images! Usually the Q7 will beat cropping a K camera. I would try using the 250-600 by itself, without the 1.4 converter. Your lens is already f5.6 at 600mm. Adding 1.4 HDTC means effectively it is f8. That is closing down pretty far with the Q7 and diffraction starts robbing sharpness.

I shoot the original Q with Pentax A*300 and almost always stop down 1 stop to f5.6. The lens is sharper 1 stop down. Imagine your lens would also be sharper 1 stop down, especially with the 1.4 teleconverter. Unfortunately, that puts you at f11 and the diffraction probably hampers sharpness considerably. Try without converter.
Thanks
barondla

Thanks for the advice, I used to do it direct with the FA250-600, but my technique wasn't good enough

Maybe I should use f6.3 to optimize sharpness ?

Also a thing that I wasn't sure, is how to set the adapter's position from 0 to 9?? I read that some just use the 1 position (which I did in these shots), but it is not clear in my mind what does those settings exactly if I manually control the aperture ring on the lens...

I will give it a try next time ...

vonBaloney · 03-25-2016, 06:46 AM

Originally posted by Weevil

Also a thing that I wasn't sure, is how to set the adapter's position from 0 to 9?? I read that some just use the 1 position (which I did in these shots), but it is not clear in my mind what does those settings exactly if I manually control the aperture ring on the lens...

Don't bother with that ring on the adapter (leave it all the way open) when using any lens that has an aperture ring of its own and just use the lens aperture ring. You only need it for newer lenses that don't have rings (and then you've got to figure out rough equivalents to apertures)...

**Weevil** · 03-25-2016, 08:22 AM

Originally posted by vonBaloney

Don't bother with that ring on the adapter (leave it all the way open) when using any lens that has an aperture ring of its own and just use the lens aperture ring. You only need it for newer lenses that don't have rings (and then you've got to figure out rough equivalents to apertures)...

OK, great thanks !

**pacerr** · 03-25-2016, 10:05 AM

Originally posted by vonBaloney

I believe it is the effective aperture that counts, i.e. even extension tubes or bellows with no optical elements can affect diffraction. Here's a debate about it:

https://www.pentaxforums.com/forums/136-pentax-q/185307-do-teleconverters-cou...-equation.html

I'm still concerned (or perhaps just confused?) over the semantics involved here.

Speaking of f-stops and effective EV doesn't address the CAUSE of diffraction which occurs at the plane of the aperture disk and is defined by the relationship between the 'size' of the aperture and the characteristics of light wave dispersion.

The OBSERVABLE EFFECT of diffraction is certainly increased as the aperture plane is moved further from the the sensor simply because you're spreading the light rays at the sensor by inserting extension tubes in the light path or optically expanding the image circle as with a TC relative to the fixed size of the pixels (film grain). Neither of which affect the aperture vs. wave length relationship at the aperture plane.

Unfortunately(?) the OBSERVABLE EFFECT on EV (the apparent f-stop) is also affected by the same extension factor but is a different physical function than diffraction.

Adding to the confusion, there's a tendency to be imprecise when using "effective aperture". Are we measuring EV or noting a function of the Airy Disk definition.

In simplest terms, the effect of diffraction can easily be described without addressing light loss (EV). The larger the relative aperture the less the total effect of diffraction -- oh, and the more difficult it becomes to design a lens with perfect conversion of all light ray paths and correction of aberrations. Damn those expensive compromises!

When we extend the distance from the sensor to the aperture disk with extension tubes, or optically 'magnify' the image on the sensor with TC's, we affect the image at the sensor plane. When we vary the aperture (the physical lens f-stop) we affect the characteristics of diffraction at the plane of the aperture.

Either factor will affect both EV and diffraction effects.

reh321 · 03-26-2016, 08:09 AM

Originally posted by vonBaloney

Don't bother with that ring on the adapter (leave it all the way open) when using any lens that has an aperture ring of its own and just use the lens aperture ring. You only need it for newer lenses that don't have rings (and then you've got to figure out rough equivalents to apertures)...

I'm wondering whether using a built-in aperture ring gives sharper pictures than using the "aperture control" on the Pentax adapter does. My reason for asking is that when I did do some backyard testing at 300mm, my Sigma 70-300mm APO lens {using its aperture ring} gave sharper results than my Pentax-DA 55-300mm {using the Pentax adapter control} did, and I wasn't positive whether the lens is actually sharper or whether the means of limiting aperture was the real issue. If I get motivated to test again, the obvious solution is to test the Sigma lens using the adapter to control aperture.

03-25-2016, 10:05 AM	#1169
pacerr Loyal Site Supporter Join Date: Jan 2008 Location: Paris, TN Photos: Gallery \| Albums Posts: 3,350	Originally posted by vonBaloney I believe it is the effective aperture that counts, i.e. even extension tubes or bellows with no optical elements can affect diffraction. Here's a debate about it: https://www.pentaxforums.com/forums/136-pentax-q/185307-do-teleconverters-cou...-equation.html I'm still concerned (or perhaps just confused?) over the semantics involved here. Speaking of f-stops and effective EV doesn't address the CAUSE of diffraction which occurs at the plane of the aperture disk and is defined by the relationship between the 'size' of the aperture and the characteristics of light wave dispersion. The OBSERVABLE EFFECT of diffraction is certainly increased as the aperture plane is moved further from the the sensor simply because you're spreading the light rays at the sensor by inserting extension tubes in the light path or optically expanding the image circle as with a TC relative to the fixed size of the pixels (film grain). Neither of which affect the aperture vs. wave length relationship at the aperture plane. Unfortunately(?) the OBSERVABLE EFFECT on EV (the apparent f-stop) is also affected by the same extension factor but is a different physical function than diffraction. Adding to the confusion, there's a tendency to be imprecise when using "effective aperture". Are we measuring EV or noting a function of the Airy Disk definition. In simplest terms, the effect of diffraction can easily be described without addressing light loss (EV). The larger the relative aperture the less the total effect of diffraction -- oh, and the more difficult it becomes to design a lens with perfect conversion of all light ray paths and correction of aberrations. Damn those expensive compromises! When we extend the distance from the sensor to the aperture disk with extension tubes, or optically 'magnify' the image on the sensor with TC's, we affect the image at the sensor plane. When we vary the aperture (the physical lens f-stop) we affect the characteristics of diffraction at the plane of the aperture. Either factor will affect both EV and diffraction effects. Attached Images

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03-14-2016, 07:09 AM	#1156
reh321 Pentaxian Join Date: Nov 2014 Location: South Bend, IN, USA Photos: Gallery \| Albums Posts: 23,185	Originally posted by pearsaab the wood ducks are back in my pond so got chance to get some with the Q, Q-k adapter always use setting 1 or less (I have found going higher does not improve the picture quality). Sigma 500mm 4.5. i either use a remote or the 2 second delay to minimize my movement Would movement actually make a difference since you are already losing some detail by shooting through a screen?

03-14-2016, 09:33 AM	#1157
barondla Site Supporter Join Date: Sep 2006 Location: midwest, United States Photos: Gallery \| Albums Posts: 5,716 Original Poster	Nice images pearsaab. The feather detail is superb. That is quite a distance to shoot. I would find that very difficult without a red dot scope. Impressive. Thanks for sharing barondla ---------- Post added 03-14-2016 at 11:41 AM ---------- reh321, the losses would combine. Whatever loss there is shooting through glass or screen, is different than sharpness loss due to movement. Notice pearsaab is using a nice, hefty tripod. It all adds up. The Q and ultra telephoto photography can be very demanding. Thanks barondla

03-14-2016, 10:02 AM	#1158
reh321 Pentaxian Join Date: Nov 2014 Location: South Bend, IN, USA Photos: Gallery \| Albums Posts: 23,185	Originally posted by reh321 Would movement actually make a difference since you are already losing some detail by shooting through a screen? Originally posted by barondla The Q and ultra telephoto photography can be very demanding. Yes, I have experiential knowledge of that. https://www.pentaxforums.com/forums/136-pentax-q/284804-baby-steps-3.html {one of the questions I've been asking lately is whether the leaf shutter in the Pentax adapter provides a boost in sharpness} When I started I was inside our den, shooting through glass, and eventually I moved out to our {cold and snowy} deck to eliminate that hindrance to sharpness; I've been doing what I can to optimize each component that affects sharpness, within the limits set by my budget I stated my question poorly, but I asked it because I thought the screen might do more harm to sharpness than the tripod did good.

03-14-2016, 01:46 PM	#1159
pearsaab Otis Memorial Pentaxian Loyal Site Supporter Join Date: May 2011 Location: Richmond, Virginia USA Photos: Gallery \| Albums Posts: 2,900	Originally posted by reh321 Yes, I have experiential knowledge of that. https://www.pentaxforums.com/forums/136-pentax-q/284804-baby-steps-3.html {one of the questions I've been asking lately is whether the leaf shutter in the Pentax adapter provides a boost in sharpness} When I started I was inside our den, shooting through glass, and eventually I moved out to our {cold and snowy} deck to eliminate that hindrance to sharpness; I've been doing what I can to optimize each component that affects sharpness, within the limits set by my budget I stated my question poorly, but I asked it because I thought the screen might do more harm to sharpness than the tripod did good. I actually have the window open and yes i have tried shooting through glass and you will definitely lose sharpness. Movement will impact the picture as well. As long as they stay in the approximate area then when i have the 2 second delay or the remote i can catch them some of the time. If they are moving fast there is no way to keep up with them especially with low shutter speeds. You must have a stable platform or you will not stand a chance to get the picture. I have never used anything but the qk adapter so don't know how critical that is.

03-14-2016, 01:56 PM	#1160
barondla Site Supporter Join Date: Sep 2006 Location: midwest, United States Photos: Gallery \| Albums Posts: 5,716 Original Poster	reh321, sorry, I see what you were asking now. Trade offs of shooting thru the screen and not using a tripod.I would say shooting through screen is better than doing without a tripod. Especially with a 500mm lens that weighs that much. Doubt anyone can shoot that combo reliably hand held. To answer your adapter question. I started with a generic. First one that came out. Recommended by snowstorm. it was horrible, but all that was available. The tripod foot broke holding a 100mm lens. The insides of the adapter were bright and shiny. Took the phono cartridge size screws and put big nuts on them. Then JB Weleded it together. Painted the inside with flat black paint. Great image improvement. Later a poster recommended black felt flocking instead of paint. That helped. More contrasty images. Then Pentax brought out their Q>PK adapter with leaf shutter. On still subjects using a tripod the sharpness between generic and Pentax are close. Pentax wins slightly, very slightly. Figure this comes down to better internal flare reduction because Pentax uses felt flocking, groves in the metal, and aperture plates. Hard to beat that. The massively stable tripod foot could also play into it. With moving subjects the Pentax adapter is considerably sharper. This also holds true for hand holding a 100 - 300mm lens. Sensor shutter has serious motion artifacts. No matter the shutter speed the sensor scans one line at a time. Take a desk fan, put it outside in bright sun pick 1/1000 or higher shutter speed. Turn fan on and photograph the fan face. It won't look like fan blades. Kind of like bizarro Superman. Hope this helps. barondla

03-14-2016, 03:10 PM - 1 Like	#1161
barondla Site Supporter Join Date: Sep 2006 Location: midwest, United States Photos: Gallery \| Albums Posts: 5,716 Original Poster	reh321, these tips were posted about a year ago in another thread. How I shoot with the original Q. 1. Use the sturdiest tripod you have. 2.Turn off SR. 3. Use wireless remote. 4. Red dot scope to speed up subject location. 5. Lowest ISO you can get away with. 6. Shoot Raw. 7. LCD set to maximum brightness. 8. LCD magnification set to 4x. 9. Auto bracketing on and set to +- .3 allows Q to shoot 3 shot burst pictures faster. 10. Plenty of extra batteries. They will be needed. If it is a fairly static subject not doing anything super special, I live with slower shutter speeds. May have to shoot a lot to get one without motion blur . Can live with that. If subject is doing someting special , higher ISO will capture it. Always use a wireless remote. Wish the Q wasn't as finicky with the rear sensor. Being mirrorless is a blessing with ultra telephoto shooting. This is how I shoot others may have their special techniques. Patience and practice are very helpful. Read more at: https://www.pentaxforums.com/forums/136-pentax-q/284585-extreme-telephoto-tip...#ixzz42ux7q8Of

03-22-2016, 10:45 PM - 1 Like	#1162
Weevil Site Supporter Join Date: May 2012 Location: Near Montréal, Québec Photos: Gallery Posts: 4,446	(xposted on the HDTC thread) Been shooting waterfowls this weekend, and had a chance to test the Q7 on my FA250-600 + HDTC 1.4x, and after reviewing all your good advises, I was able to get some interesting results... The 2 next Photos taken with Pentax K-3 + FA250-600 @ 600mm. The 1.5x crop factor gives a 900mm FF equivalent. photos are the original size (not cropped) from the K-3. Bernache nonnette / Barnacle Goose [Branta leucopsis] by Sylvain Cote, sur Flickr Bernache nonnette / Barnacle Goose [Branta leucopsis] by Sylvain Cote, sur Flickr Photo taken with Pentax K-3 + HDTC 1.4x + FA250-600 @ 600mm (840mm). The 1.5x crop factor of the K-3 gives a 1260mm FF equivalent. This photo is the original size (not cropped) from the K-3. Bernache nonnette / Barnacle Goose [Branta leucopsis] by Sylvain Cote, sur Flickr Photo taken with Pentax Q7 + Q-K Adapter on FA250-600 + HDTC 1.4x. The Lens + HDTC1.4x = 840mm (1260mm equivalent on a APS-C sensor), combined with the 4.59x crop factor of the Q7 sensor (Sensor size is 1/1.7" or 7.44 x 5.58 mm), that gives a total of 840mm x 4.59 = 3856mm !!! I dont have to tell you that I am using a very sturdy tripod, and a IR remote shutter release to minimize the vibrations. This photo is the original size (not cropped) from the Q7. Bernache nonnette / Barnacle Goose [Branta leucopsis] by Sylvain Cote, sur Flickr However, do I get more details if I crop the 24mp image from the K-3 + HDTC ? not sure... this is an example of a crop image taken with the K-3 + HDTC + FA-250-600 Bernache nonnette / Barnacle Goose [Branta leucopsis] by Sylvain Cote, sur Flickr a bit less crop here.. Bernache nonnette / Barnacle Goose [Branta leucopsis] by Sylvain Cote, sur Flickr

03-24-2016, 09:42 PM	#1163
barondla Site Supporter Join Date: Sep 2006 Location: midwest, United States Photos: Gallery \| Albums Posts: 5,716 Original Poster	Weevil, nice images! Usually the Q7 will beat cropping a K camera. I would try using the 250-600 by itself, without the 1.4 converter. Your lens is already f5.6 at 600mm. Adding 1.4 HDTC means effectively it is f8. That is closing down pretty far with the Q7 and diffraction starts robbing sharpness. I shoot the original Q with Pentax A*300 and almost always stop down 1 stop to f5.6. The lens is sharper 1 stop down. Imagine your lens would also be sharper 1 stop down, especially with the 1.4 teleconverter. Unfortunately, that puts you at f11 and the diffraction probably hampers sharpness considerably. Try without converter. Thanks barondla

03-24-2016, 10:53 PM	#1164
pacerr Loyal Site Supporter Join Date: Jan 2008 Location: Paris, TN Photos: Gallery \| Albums Posts: 3,350	Originally posted by barondla Adding 1.4 HDTC means effectively it is f8. That is closing down pretty far with the Q7 and diffraction starts robbing sharpness. ; Yes, but . . . have you actually "closed down" the size of the aperture? Diffraction is a function of the physical 'size' of the aperture, no? As the aperture is closed down the proportional difference between the total AREA of the 'hole' and the diffraction-producing circumference of the rim of the hole changes. Radius-squared vs. (radius x 2) X 3.14 (pi). The one-to-two stop EV loss with a TC is a function of the total light lost to the sensor (cropped image spill over and additional glass) rather than a physical change to the size of the lens aperture itself. While it does affect exposure I don't believe it affects the parameters for diffraction. I may be wrong about that but it's been my understanding of the situation. Sensor and pixel size are another issue.

03-25-2016, 06:28 AM	#1165
vonBaloney Pentaxian Join Date: Oct 2011 Location: Albuquerque, NM Posts: 6,029	Originally posted by pacerr ; Yes, but . . . have you actually "closed down" the size of the aperture? Diffraction is a function of the physical 'size' of the aperture, no? As the aperture is closed down the proportional difference between the total AREA of the 'hole' and the diffraction-producing circumference of the rim of the hole changes. Radius-squared vs. (radius x 2) X 3.14 (pi). The one-to-two stop EV loss with a TC is a function of the total light lost to the sensor (cropped image spill over and additional glass) rather than a physical change to the size of the lens aperture itself. While it does affect exposure I don't believe it affects the parameters for diffraction. I believe it is the effective aperture that counts, i.e. even extension tubes or bellows with no optical elements can affect diffraction. Here's a debate about it: https://www.pentaxforums.com/forums/136-pentax-q/185307-do-teleconverters-cou...-equation.html

03-25-2016, 06:33 AM	#1166
Weevil Site Supporter Join Date: May 2012 Location: Near Montréal, Québec Photos: Gallery Posts: 4,446	Originally posted by barondla Weevil, nice images! Usually the Q7 will beat cropping a K camera. I would try using the 250-600 by itself, without the 1.4 converter. Your lens is already f5.6 at 600mm. Adding 1.4 HDTC means effectively it is f8. That is closing down pretty far with the Q7 and diffraction starts robbing sharpness. I shoot the original Q with Pentax A*300 and almost always stop down 1 stop to f5.6. The lens is sharper 1 stop down. Imagine your lens would also be sharper 1 stop down, especially with the 1.4 teleconverter. Unfortunately, that puts you at f11 and the diffraction probably hampers sharpness considerably. Try without converter. Thanks barondla Thanks for the advice, I used to do it direct with the FA250-600, but my technique wasn't good enough Maybe I should use f6.3 to optimize sharpness ? Also a thing that I wasn't sure, is how to set the adapter's position from 0 to 9?? I read that some just use the 1 position (which I did in these shots), but it is not clear in my mind what does those settings exactly if I manually control the aperture ring on the lens... I will give it a try next time ...

03-25-2016, 06:46 AM	#1167
vonBaloney Pentaxian Join Date: Oct 2011 Location: Albuquerque, NM Posts: 6,029	Originally posted by Weevil Also a thing that I wasn't sure, is how to set the adapter's position from 0 to 9?? I read that some just use the 1 position (which I did in these shots), but it is not clear in my mind what does those settings exactly if I manually control the aperture ring on the lens... Don't bother with that ring on the adapter (leave it all the way open) when using any lens that has an aperture ring of its own and just use the lens aperture ring. You only need it for newer lenses that don't have rings (and then you've got to figure out rough equivalents to apertures)...

03-25-2016, 08:22 AM	#1168
Weevil Site Supporter Join Date: May 2012 Location: Near Montréal, Québec Photos: Gallery Posts: 4,446	Originally posted by vonBaloney Don't bother with that ring on the adapter (leave it all the way open) when using any lens that has an aperture ring of its own and just use the lens aperture ring. You only need it for newer lenses that don't have rings (and then you've got to figure out rough equivalents to apertures)... OK, great thanks !

03-26-2016, 08:09 AM	#1170
reh321 Pentaxian Join Date: Nov 2014 Location: South Bend, IN, USA Photos: Gallery \| Albums Posts: 23,185	Originally posted by vonBaloney Don't bother with that ring on the adapter (leave it all the way open) when using any lens that has an aperture ring of its own and just use the lens aperture ring. You only need it for newer lenses that don't have rings (and then you've got to figure out rough equivalents to apertures)... I'm wondering whether using a built-in aperture ring gives sharper pictures than using the "aperture control" on the Pentax adapter does. My reason for asking is that when I did do some backyard testing at 300mm, my Sigma 70-300mm APO lens {using its aperture ring} gave sharper results than my Pentax-DA 55-300mm {using the Pentax adapter control} did, and I wasn't positive whether the lens is actually sharper or whether the means of limiting aperture was the real issue. If I get motivated to test again, the obvious solution is to test the Sigma lens using the adapter to control aperture.