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10-21-2010, 12:49 PM   #1
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Extreme-telephoto?!? AF or MF??

Good morning to all,
I would like to ask you a question, that does not give me peace ...

The extreme tele, are better AutoFocus (AF) or manual focus (MF), this stems from the fact that I wanted one.
I have already a A * 300 mm F/2.8, but I never use, this because I love "retain/keep" to better lenses, like in a museum.
I have the chance to have a A * 400 mm F/2.8, one here in the Forum, and one in Italy next to me.
Then always in my country, a A * 500 mm f/5.6, and continents away an FA * 250-600 mm.

Here's the point is that I don't know what to choose, and I ask your help.

FA * 250-600 mm, I really like the fact that both zoom and Autofocus,
I don't like that is f/5.6, and that and which the seller declares dust, internal ...

A * 400 mm, I like the fact that both F/2.8, which is "mighty" has a huge front lens in the world, there are very few 400 so bright.
Since f/2.8 can multiply to 2 x, having a 800 mm F/5.6 on Aps-c 1200mm F/5.6
I don't like it, some say on aps-c a 600 F/2.8 is little usable at F/2.8 shallow depth of field.


A * 600 mm F/5.6, talks about it all well even all open.
I'm afraid that is dark, and I'm afraid that not being zoom, I could be "long" or "short".

Other my fear that having a long 600 mm focal so, have a MF lens, is slow, that is, the birds are fast, even if I wanted to photograph a person, who speaks moves the head quickly.

However, there are those who say that also AF lenses, are not always so clear, and I think that's true.

Now tell me, your opinions/thoughts, to understand what lens to buy

Thanks everyone, in advance, for courtesy.

10-21-2010, 12:54 PM   #2
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I would have to question where you are heading,

if I had an A300F2.8 i would certainly use it, most likely with the 1.7x AF TC

I p[resently use the TC with my K300F4 and the A300F2.8 woould give just enough more light to make me happy.

If you don;t like that combo, I doubt you will be happy with anything else in your post.

While all fast lenses are shallow DOF, you don't always use them wide open.

As to MF or AF, if you are shooting through branches (wildlife) AF is really hard to use because it will focus on everything in the line of sight not what you are fixated on.

just my $0.02. BTW if you really don't use the A300F2.8 send me a PM I moght be interested.
10-21-2010, 01:27 PM   #3
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I have seen hundreds of threads in this forum where somebody wants advice on which lens is best for them. Almost none of the OPs include a word about their REQUIREMENTS. Without that, there is no solution because the problem is not defined.
Examples;
- Will your subjects be in motion? AF is a great help (I use the AF 1.7x TC when AF is required).
- Will you have to carry it far? Weight comes into play.
- Using a 2x TC with its 2-stop penalty means the faster lens will be required for high shutter speeds if you normally shoot against dark backgrounds.
- Will you need a zoom or will you typically just max the telephoto anyway?
- How much zoom do you need? Counting on a 2x TC means planning on leaving a noticable chunk of IQ behind.


If you don't know where you want to go....any road will get you there. Try asking this question again along with exactly what you want to do with the lens. The Forum has a thread just to discuss super telephoto lenses if you want to post your question and requirements there

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/55946-300mm-pl...lenses-53.html

btw, I use the A*400/2.8 with 1.4xL, 1.7xAF and 2xL TCs. If it were a 100-400mm lens I would still shoot at 400mm all the time.
10-21-2010, 02:57 PM   #4
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Hello
I'll try to help you as I'm birding too with a Pentax Fa*600f4; for me AF is definitively required for extreme telephoto, because depth of field for these lenses is very shallow and it is almost impossible to focus properly in manual mode; I sometimes uses the lens with a Sigma f1.4 converter that retains AF, and I'll sell my Pentax 1.4L converter, which is better optically but not usable on a 600 mm cause I don't manage to get proper focus.
I have owned a A*300 f2.8, a very good lens, I have sold it to fund the FA*600 recently; I used to use it with the AF A.7 converter; this gives a good 500 f4.5 lens, albeit with some purple fringing in extreme contrast situation. If you have the opportunity to buy a 1.7 AF converter, jump on it !
The 250-600 mm seems to have very good IQ and it is AF; F5.6 is not really an issue, I always stop down the 600f4 at f5.6 or better at f8 to get more depth of field. At f4, 6 to 8 meters away, for small birds, depth of field is around 1 cm - far too small; if you focus on the eye, the wings are blurred, and vice-versa.
Keep in mind that the min focus distance of the 600 f5.6 is about 6 meters; that can be too much for birding. Using a TC on a shorter lens as a 300 f2.8 or a 400 is a good option.
The 250-600 has the advantage that you can locate the bird at 250 mm, and then zoom to 600; finding a bird in the viewfinder with a 600 is tricky;
I would not rely on a 2x TC; IQ degradation is not acceptable for me; even with the dedicated Pentax 2xL converter there was a blue halo around white birds that is impossible to remove with PP.
Hope that helps; have a look on some of my last posts :
Tired of photokina bashing threads; flycatcher season with FA*600: Pentax SLR Talk Forum: Digital Photography Review

Bird shots with FA*600: Pentax SLR Talk Forum: Digital Photography Review

10-21-2010, 03:55 PM   #5
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QuoteOriginally posted by bollicina31 Quote
Good morning to all,
I would like to ask you a question, that does not give me peace ...

The extreme tele, are better AutoFocus (AF) or manual focus (MF), this stems from the fact that I wanted one.
I have already a A * 300 mm F/2.8, but I never use, this because I love "retain/keep" to better lenses, like in a museum.
I have the chance to have a A * 400 mm F/2.8, one here in the Forum, and one in Italy next to me.
Then always in my country, a A * 500 mm f/5.6, and continents away an FA * 250-600 mm.

Here's the point is that I don't know what to choose, and I ask your help.

FA * 250-600 mm, I really like the fact that both zoom and Autofocus,
I don't like that is f/5.6, and that and which the seller declares dust, internal ...

A * 400 mm, I like the fact that both F/2.8, which is "mighty" has a huge front lens in the world, there are very few 400 so bright.
Since f/2.8 can multiply to 2 x, having a 800 mm F/5.6 on Aps-c 1200mm F/5.6
I don't like it, some say on aps-c a 600 F/2.8 is little usable at F/2.8 shallow depth of field.


A * 600 mm F/5.6, talks about it all well even all open.
I'm afraid that is dark, and I'm afraid that not being zoom, I could be "long" or "short".

Other my fear that having a long 600 mm focal so, have a MF lens, is slow, that is, the birds are fast, even if I wanted to photograph a person, who speaks moves the head quickly.

However, there are those who say that also AF lenses, are not always so clear, and I think that's true.

Now tell me, your opinions/thoughts, to understand what lens to buy

Thanks everyone, in advance, for courtesy.
The only thing this crew at PF may fear is the price of a A* 600mm lens or FA* 250-600 lens.
10-21-2010, 07:22 PM   #6
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One old guy's opinion here, but birds and AF don't work for me. A bird in the bush causes the AF to focus beautifully on the bush, ignoring the bird. AF is not as selective as manual focus. I want the lens to focus on what I want in focus, and AF cannot be relied upon to do that. For Birds In Flight, AF works because nothing is in the lens but the bird, but in most cases the AF lens will focus on a nice sharp edge rather than the animal, bird or whatever.
10-21-2010, 08:19 PM   #7
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QuoteOriginally posted by Canada_Rockies Quote
One old guy's opinion here, but birds and AF don't work for me. A bird in the bush causes the AF to focus beautifully on the bush, ignoring the bird. AF is not as selective as manual focus. I want the lens to focus on what I want in focus, and AF cannot be relied upon to do that. For Birds In Flight, AF works because nothing is in the lens but the bird, but in most cases the AF lens will focus on a nice sharp edge rather than the animal, bird or whatever.
That's why I go manual focus also when shooting birds. Having a lens that'll do both is a true pleasure because there are situation where autofocus is great to have.
10-21-2010, 09:03 PM   #8
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+1 to what goubejp has to say about AF.
I would never have been able to shoot this sunbird if it were not for AF. This little bird is only about 2 inches and flitters about from flower to flower faster than one can focus manually. Image is uncropped.



10-22-2010, 06:23 AM   #9
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QuoteOriginally posted by creampuff Quote
+1 to what goubejp has to say about AF.
I would never have been able to shoot this sunbird if it were not for AF. This little bird is only about 2 inches and flitters about from flower to flower faster than one can focus manually. Image is uncropped.
Nice done ! What lens did you use ?
10-22-2010, 06:39 AM   #10
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My M 400/5.6 is the only lens I have which qualifies as “extreme” telephoto. It is manual focus of course with all the shortcomings of the M series: no AE/AF or low dispersion glass. That said it works very well for the purpose I mainly use it for – birding. As others have noted above there is no hunt of peck when focusing this beast. I installed a KatzEye screen specifically to help with manual focus and it works quite well. In a recent shot of this Robin I suspect AF would have zeroed in on the berries:



I can’t say I wouldn’t prefer the convenience of a more modern Pentax DA* 400/4 if they ever make one. I would still want to be able to manually override the AF when I wanted to however.

Last edited by 8540tomg; 10-22-2010 at 07:03 AM. Reason: typo
10-22-2010, 08:02 AM   #11
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In my experience, the necessity of autofocus increase with focal length.
I've had both an M-400/5.6 and a K-500/4.5, and found them tough to operate. However I borrowed a A*400/2.8 for a day at an air show once, and was able to shoot at least a few in-focus pics of the passing spitfire planes. Manual focus operation is much smoother on the A* series, I guess. Since then I've had a FA*400/5.6, and now own a FA*600/4. After experiencing these I wouldn't even consider going back to manual focus for any tele lens.

However I agree with your suspicion about the internal dust in the FA*250-600. That doesn't sound good. Cleaning that beast could be costly.
10-22-2010, 08:06 AM   #12
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QuoteOriginally posted by goubejp Quote
Nice done ! What lens did you use ?
K7 with DA 55-300mm
10-22-2010, 08:06 AM   #13
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QuoteOriginally posted by creampuff Quote
+1 to what goubejp has to say about AF.
I would never have been able to shoot this sunbird if it were not for AF. This little bird is only about 2 inches and flitters about from flower to flower faster than one can focus manually. Image is uncropped.
It's a beautiful photo, but if you really examine it, the stem he's hanging onto is more in focus than the bird.
10-22-2010, 08:47 AM   #14
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I have a MF 800 that has about 330 degrees of rotation on the focus barrel. If you are going from near to far, it can take about 5 seconds of twisting to get there...

If the subject is moving, forget it. Had about 1 keeper in 50 surf shots.
10-22-2010, 04:29 PM   #15
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QuoteOriginally posted by Ira Quote
It's a beautiful photo, but if you really examine it, the stem he's hanging onto is more in focus than the bird.
Better than no shot of the bird had I tried to focus manually... btw I have other shots as well that are pin sharp...
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