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12-14-2012, 05:47 PM   #1
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Adapted Lenses - is faster better?

I'm trying to get my head around the diffraction term that is associated with adapted lenses used on the Q. Also trying to figure out if faster lenses are better or not - not sure if this is related to the diffraction issue or not.

So to simplify this for myself, here is a simple question.....

What would work better on the Q - a 300mm f4 (F4.5) lens or a 300mm 2.8 lens?

12-14-2012, 05:51 PM   #2
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QuoteOriginally posted by stormtech Quote
I'm trying to get my head around the diffraction term that is associated with adapted lenses used on the Q. Also trying to figure out if faster lenses are better or not - not sure if this is related to the diffraction issue or not.

So to simplify this for myself, here is a simple question.....

What would work better on the Q - a 300mm f4 (F4.5) lens or a 300mm 2.8 lens?
You need lenses with high resolving power that are sharp wide-open, and unfortunately such lenses are few and far between (not to mention heavy & expensive). You'll probably get better results with an F2.8 lens, but I think the only real way to find it is to do an empirical test.

Adam
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12-14-2012, 06:30 PM   #3
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What Adam said.
In practice I am finding that you really just have to try each lens.
We assumed the DA*200 was going to be a great candidate but some that have tried it have been less than satisfied.
My DA*300 and Sigma 70-200 2.8 I prefer at 5.6 on the Q.
And my DFA100WR I run at slower stops for greater DOF in macro.
12-14-2012, 07:11 PM   #4
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Thanks for the feedback guys. I get to thinking of the possibilities with the Q quite a bit lately, and the thought came about a 300 2.8 lens.

Since I got good results with my FA* 300 4.5 lens, I guess I should just leave it at that. Maybe one stop would help with ISO or shutter speed, but I guess the absolute resolving power or IQ is king with this combination. I guess nobody has tried a 300 2.8 lens yet.

12-14-2012, 08:24 PM   #5
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It is more complicated than diffraction. As an example, I have a 350 2.8 Olymus OM lens ( originally designed for film). On an Olympus 4/3 or M4/3 body it tends to beat out my Pentax DA*300 on a K body. That approx 5" front element does things for resolution that a 3" lens has a hard time matching.

Put both lenses on the Q and the results flip flop. Pushing the lenses this hard causes a lot of purple fringing on the OM lens and virtually none on the Pentax DA*300. The Pentax lens has been color corrected to a greater degree. The only lens I have used that beats the Pentax for fringing is a specially tweaked mirror lens. No surprise since mirrors don't have false color. Still need to try the OM 180 2 more. It has less color than the 350 for sure. Also need to try the 350 closed down to the 5.6 range. When testing it originally I thought everything had to be at 2.8 for diffraction control. Thanks to snostorm, I have been using the Pentax DA55-300 and getting nice results at 5.8.

If I were buying an expensive lens for non Q use, would still put it on the Q as a test. It really brings out the differences in lenses. It is a lens microscope.
thanks
barondla

Next up is more experienting with the mirror and trying a telecompressor to gain lens speed.
12-14-2012, 08:46 PM   #6
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Thanks for the additional input barondia - I'm learning as I go here.
12-14-2012, 10:34 PM   #7
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No problem. You have some top candidates for the Q. 300 should rock. Hear good things about the 100 macro and 60-250. Curious about the 55. Have you tried it yet?
thanks
barondla
12-14-2012, 10:38 PM   #8
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QuoteOriginally posted by stormtech Quote
guess nobody has tried a 300 2.8 lens yet.
Hi Stan,

I've shot with a Tamron SP 300 f2.8 and a Sigma EX 300 f2.8 APO, early in the spring, and wasn't as impressed as I had thought I'd be, but I was struggling with MF a bit and shooting only at f2.8, so I know that I need to retest these. After being somewhat disappointed with these, I didn't even try the FA* 300 f2.8. I truly think that Focus Peaking makes a big difference. Being able to watch the focus plane travel across the screen when focusing shows the precision needed to get the most out of the Q with adapted lenses. I plan on retrying all the lenses that I'd previously put aside and see if truly precision focusing will make a difference, and I really think it will.

At first, everyone expected the really fast lenses would shine when adapted to the Q because of the diffraction thing. At f2.8, contrast is usually lower then stopped down, and very very few fast tele lenses are sharpest at f2.8. Even with Focus Peaking, MF at f2.8 might be a bit more difficult because of the lower contrast, so when I test these lenses again, it will be stopped down at least a stop to start, and I'll test all the lenses up to about f8 to see how they truly stack up. I think that realizing that our lenses can actually improve with stopping down past f4 will cause a significant paradigm shift in shooting with adapted lenses and the Q. I'm looking forward to this. Cant wait until spring. . .again. . .

As to the question in the thread title, I have to say yes, though I can't prove it at this time. The faster lenses are designed with less compromise optically, and usually built to tighter tolerances since they don't have as much of a price point limitation. Higher resolution should win out in the end, and faster lenses are generally better lenses, so they should be with the Q.

Scott


Last edited by snostorm; 12-14-2012 at 10:50 PM.
12-14-2012, 10:52 PM   #9
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Snostorm, do you find the Sigma and Tammy better than the Pentax 300 2.8, or did you just decide the first two were lacking so the Pentax probably wouldn't fare much better? Just curious.
thanks
barondla
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12-15-2012, 01:41 AM   #10
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QuoteOriginally posted by barondla Quote
Snostorm, do you find the Sigma and Tammy better than the Pentax 300 2.8, or did you just decide the first two were lacking so the Pentax probably wouldn't fare much better? Just curious.

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Hi barondla,

No, the Fa* 300 f2.8 is a gem -- considerably better lens than the Tamron, and noticeably better than the Sigma. I just thought that I needed to figure out what I needed to do to get the best results before I dragged the beast out -- and then never got around to it. A consistently too hot summer and some problems with both knees kept me from using a lot of the heavier gear, if I could get out at all. The mobility problems caused me to leave the heavier gear home and move towards piecing together a much lighter overall kit, and my K-5 was getting lonely and complaining so I introduced it to the K converted Canon FD 300/4 L with the 1.7x AFA, so now they're friends.

Now that I think I've got Peaking figured out, and I'm not held back by the wide open only paradigm, I'm motivated to start retesting. I'll probably do some this winter indoors now that I can use flash without wondering if blur from the 1/13 sync was negatively effecting the results. I also have a new K-5 IIs to play with, so I should be kept busy this winter.

BTW, did you see the post I added to the https://www.pentaxforums.com/forums/pentax-q/206927-external-flash-adapted-lenses.html thread?

Scott
12-15-2012, 05:42 AM   #11
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Yes, it is very interesting and informative. Warming up the flash and camera at a certain shutter speed is a weird way to build a flash system. P-ttl is a little better. Ricoh still needs to refine the P-ttl system for ALL Pentax cameras.
thanks
barondla
12-15-2012, 07:28 AM   #12
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QuoteOriginally posted by snostorm Quote
Hi Stan,

I've shot with a Tamron SP 300 f2.8 and a Sigma EX 300 f2.8 APO, early in the spring, and wasn't as impressed as I had thought I'd be, but I was struggling with MF a bit and shooting only at f2.8, so I know that I need to retest these. After being somewhat disappointed with these, I didn't even try the FA* 300 f2.8. I truly think that Focus Peaking makes a big difference. Being able to watch the focus plane travel across the screen when focusing shows the precision needed to get the most out of the Q with adapted lenses. I plan on retrying all the lenses that I'd previously put aside and see if truly precision focusing will make a difference, and I really think it will.

At first, everyone expected the really fast lenses would shine when adapted to the Q because of the diffraction thing. At f2.8, contrast is usually lower then stopped down, and very very few fast tele lenses are sharpest at f2.8. Even with Focus Peaking, MF at f2.8 might be a bit more difficult because of the lower contrast, so when I test these lenses again, it will be stopped down at least a stop to start, and I'll test all the lenses up to about f8 to see how they truly stack up. I think that realizing that our lenses can actually improve with stopping down past f4 will cause a significant paradigm shift in shooting with adapted lenses and the Q. I'm looking forward to this. Cant wait until spring. . .again. . .

As to the question in the thread title, I have to say yes, though I can't prove it at this time. The faster lenses are designed with less compromise optically, and usually built to tighter tolerances since they don't have as much of a price point limitation. Higher resolution should win out in the end, and faster lenses are generally better lenses, so they should be with the Q.

Scott
Thanks for your input Scott!

I guess a lot of this is uncharted territory which is a lot of fun and a challenge for all of us - pretty neat actually.

Like I posted in another thread, I had very promising results with my first testing with my FA* 300 4.5 so I will continue to work with what I have. Just too much time to think about it and not actually do anything serious for another few months until the weather is fit enough for me to spend a whole day outside.....
12-17-2012, 09:08 AM   #13
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I'm really curious how all of my lenses are going to work with the Q. I don't have anything terribly expensive, but what I have I think would possibly be a good match for the Q.

These in particular I want to try:
F50 1.7 (hoping to use this as a super fast telephoto for live music)
Tamron 28-75 f2.8
Promaster/Pentax 100mm f3.5 Macro (AF)
40mm f2.8 XS (snub-nosed telephoto!)

All of these lenses are extremely sharp, and rather fast, so I'm hoping they'll work well. I also have an f8 mirror I want to try just for shits and giggles.

Since I'll be waiting at least a week for my order to come in... any idea the results I can expect from these lenses?

Charles.
12-17-2012, 09:51 AM   #14
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The only one of your lenses I own is the Tamron 28-75. It performs well as far as IQ adapted on the Q, but hand held it can be frustrating since the manual focus action is so short.

Close to your others I have the DA40 LTD - it shows a bit of CA on the Q, but is fun to use since it is so tiny and manual focus is nice.

I have an FA50 1.4 , manual focus is easy, and stopped down to f2 is wonderful. Wide open is a bit soft and shows some fringing.

I suspect your 100mm should perform well for macro, if it has any bad tendencies as a telephoto they may be more evident on the Q
12-17-2012, 10:30 AM   #15
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I've actually found the Auto-110 50mm/2.8 lens to be a great match for the Q (with adapter of course). There is no aperture control, but if you have a older lensbaby aperture disc it drops in perfectly into the adapter for maybe close to 5.6 in bright light. It's a sharp 275mm effective lens!
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