Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
12-11-2008, 11:40 AM   #31
Site Supporter
igor's Avatar

Join Date: Dec 2008
Location: USA and Europe
Posts: 555
Original Poster
Thanks for the input guys, appreciate your comments.
I have a bad back too, so my weight limit is 3-3.5kg lens
300/2.8 and 600/5.6 fit into this category, so I'm considering them first.
400/5.6 is nice and light but too short/slow.

12-11-2008, 11:54 AM   #32
Veteran Member
palmor's Avatar

Join Date: Dec 2006
Location: North of Boston, MA
Posts: 798
QuoteOriginally posted by Lowell Goudge Quote
ps, lets hope the boat we are in is not the titanic
I hope we aren't either! I think we took/taking very similar paths to long'ish glass. We comment on the same types of threads over and over

This thread got me looking around and I think a great compromise would be if Pentax would come out with a 1.7x TC of very high quality to pair with the DA* 300mm. I was looking at the Nik equivalent and some of the photos I found where pretty amazing with their 300mm f/4 lens and 1.7x TC combo

example
Whinchat photo - uri avitan photos at pbase.com

The availability/variety of stuff the other makers have makes me jealous
12-11-2008, 06:34 PM   #33
Site Supporter
Marc Langille's Avatar

Join Date: Dec 2006
Location: NW Arkansas, USA
Posts: 4,702
QuoteOriginally posted by Lowell Goudge Quote
marc whay about the sigma 300F2.8? how do you think it compares to the FA
Hi Lowell, sorry I missed answering this earlier. Here are some thoughts...

Base on feedback and it's rating (an EX lens, which is Sigma's premier lens line), it's a great lens. I can heartily recommend the 500/4.5 EX DG for sharpness! Very sharp, nice contrast, etc. My understanding is that the Sigma is sharp wide open (like my FA* 300/2.8, which is incredibly sharp at 2.8). The only reason I didn't buy the Sigma: the FA* 300/2.8 was just $300 more, so I pulled the trigger on the Pentax.

The only complaints of note for the Sigma is the relatively small footprint for the tripod collar mount (similar to FA). I have a Wimberly P30 plate, so it does quite well on the tripod, and no issues directly attached on a monopod. Some folks believe the lens hood design could be better. I am a fan of the screw on lens hood of the FA - it's almost 5 " long - very deep & solid build. It's also difficult to get sunlight hitting the front element. The FA also has a protective 112mm front filter, which is awesome.

Bottom line is that the Sigma is a great lens according to most folks' accounts. I know it's got 9 blades, so backgrounds should be pleasing to the eye. No major weaknesses, just minor stuff, from what I've seen and read.

Regards,
Marc
12-11-2008, 06:46 PM   #34
Site Supporter
Marc Langille's Avatar

Join Date: Dec 2006
Location: NW Arkansas, USA
Posts: 4,702
QuoteOriginally posted by igor Quote
Thanks m8o, the links were very helpful, and thanks for the compliments on my shots.

Thanks Lowell, which lens IYO is better optically 300/2.8 Sigma or Pentax FA ?
Igor: would it help if I post sample images taken with my FA* 300/2.8?

Regards,
Marc

12-12-2008, 01:15 AM   #35
Site Supporter
igor's Avatar

Join Date: Dec 2008
Location: USA and Europe
Posts: 555
Original Poster
Marc, sure, this will be great! With 100% center crops please.

QuoteOriginally posted by Marc Langille Quote
Igor: would it help if I post sample images taken with my FA* 300/2.8?

Regards,
Marc
12-12-2008, 04:22 AM   #36
Pentaxian




Join Date: Jun 2008
Location: Flyover America
Posts: 4,475
QuoteOriginally posted by m8o Quote
I have to think he's including sensor crop in his equation as he stated "equivalent" in his 1st post in this thread; which muddies the waters IMO as noone else does [noone has here in this discussion] when identifying focal length, but I didn't want to bring the thread off-track & say anything.
OK. Here's the actual true physical focal length of my scopes at prime focus:
500,510.560,620,1000mm.

BTW conventional telephotos don't give true prime focus FL.
For instance the Sigma "500mm" prime's over-all length is about 350mm. Of course the focal point is outside the body of the lens but not by 150mm. The reason is that they use a telephoto group on the back end of the lens who's only purpose is to reduce the physical length. This lens group is a negative focus lens rather like a TC or a barlow on an astro scope. So, in effect this lens has a built-in TC. In other words this len's "500mm" is a equivalent FL and not a true 500mm prime focus long lens like a scope is.

Last edited by wildman; 12-12-2008 at 04:42 AM.
12-12-2008, 08:08 AM   #37
Site Supporter
Marc Langille's Avatar

Join Date: Dec 2006
Location: NW Arkansas, USA
Posts: 4,702
Hi Igor,

Let me know if this is enough?

Taken at F/7.1, 1/1000 sec., ISO 1250, EV -0.7, M mode using the K20D + FA* 300/2.8 using the "Kirk Fat Bean Bag special setup" (my window ledge inside the SUV):


Crop at close to 100%:


Regards,
Marc
12-12-2008, 08:48 AM   #38
m8o
Veteran Member
m8o's Avatar

Join Date: Jul 2007
Location: 40-55'-44" N / 73-24'-07" W [on LI]
Photos: Gallery | Albums
Posts: 3,102
QuoteOriginally posted by wildman Quote
BTW conventional telephotos don't give true prime focus FL.
For instance the Sigma "500mm" prime's over-all length is about 350mm. Of course the focal point is outside the body of the lens but not by 150mm. The reason is that they use a telephoto group on the back end of the lens who's only purpose is to reduce the physical length. This lens group is a negative focus lens rather like a TC or a barlow on an astro scope. So, in effect this lens has a built-in TC. In other words this len's "500mm" is a equivalent FL and not a true 500mm prime focus long lens like a scope is.
What's the net? Is not the object size projected onto the sensor the same with the 500mm "compacted design" as it is with the "full extended length design"?

Marc. Phenomenal!

12-12-2008, 02:55 PM   #39
Pentaxian
rvannatta's Avatar

Join Date: Aug 2007
Location: Apiary, Oregon
Photos: Gallery
Posts: 1,176
QuoteOriginally posted by igor Quote
m8o and Russell, thanks for the input.
I still haven't heard a single comment about the Pentax 600mm f/5.6 lens... This one was among my first candidates...any opinions? reviews? whatever.
I own one, but it is a pretty old lens, and never made in auto focus.

I think the 600 F/4 sort of over shadowed it. Pentax made some dedicated
converters for their long lenses, but alas they are not auto focus either.

auto focus tends to be limited in usefulness when pushing the limits
anyway, however because it usually won't work right at f stops smaller than
about 5.6 so if you add a converter there isn't enough light for the auto focus to work anyway if you start with an f 5/6 lens.
12-12-2008, 03:25 PM   #40
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,400
QuoteOriginally posted by wildman Quote
OK. Here's the actual true physical focal length of my scopes at prime focus:
500,510.560,620,1000mm.

BTW conventional telephotos don't give true prime focus FL.
For instance the Sigma "500mm" prime's over-all length is about 350mm. Of course the focal point is outside the body of the lens but not by 150mm. The reason is that they use a telephoto group on the back end of the lens who's only purpose is to reduce the physical length. This lens group is a negative focus lens rather like a TC or a barlow on an astro scope. So, in effect this lens has a built-in TC. In other words this len's "500mm" is a equivalent FL and not a true 500mm prime focus long lens like a scope is.
Just as a simple clarification, the word telephoto means a lens which has a magnification factor equal to that of a simple lens but has reduced overall length.

if you look at the SMC 500 F4.5 it is not a telephoto lens, just a long lens.
12-14-2008, 11:40 AM   #41
Site Supporter
igor's Avatar

Join Date: Dec 2008
Location: USA and Europe
Posts: 555
Original Poster
That's more than impressive, Marc, thanks!

QuoteOriginally posted by Marc Langille Quote
Hi Igor,

Let me know if this is enough?

Marc
12-14-2008, 11:44 AM   #42
Site Supporter
igor's Avatar

Join Date: Dec 2008
Location: USA and Europe
Posts: 555
Original Poster
Thanks for the info , rvannatta.

QuoteOriginally posted by rvannatta Quote
I own one, but it is a pretty old lens, and never made in auto focus.

I think the 600 F/4 sort of over shadowed it. Pentax made some dedicated
converters for their long lenses, but alas they are not auto focus either.

auto focus tends to be limited in usefulness when pushing the limits
anyway, however because it usually won't work right at f stops smaller than
about 5.6 so if you add a converter there isn't enough light for the auto focus to work anyway if you start with an f 5/6 lens.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
k-mount, lens, lenses, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Best choice for a long, prime portrait lens? m88k Pentax SLR Lens Discussion 23 08-11-2010 03:13 PM
thinking about long tele prime neweinstein Pentax SLR Lens Discussion 16 01-20-2010 02:10 PM
Some fun with the long tele pingflood Post Your Photos! 12 05-18-2009 09:37 AM
If you're looking for a LONG fixed tele, look at what I saw at KEH... heatherslightbox Pentax SLR Lens Discussion 8 08-01-2008 06:46 AM
Super Tele Lens Choice Gerrys Pentax SLR Lens Discussion 27 04-22-2008 02:07 PM



All times are GMT -7. The time now is 03:05 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top