[SaltyPentax]

Hi Pentax friends,

So I just purchased an OS HSM Bigma and am rather shocked to find that cropping my Tamron 70-200 2.8 most often yields better results... The Bigma might have a slight advantage around f10 and 450mm - but it's slight and the planets need to align first. To me, the Tamron certainly renders better - OOF areas, clouds, busy branches... that sort of stuff... Am I missing a trick with the Bigma?

I recently sold my 60-250 but have just repurchased one so it will be interesting to see how that fits into the mix. I'm hoping with the 1.4 HD converter, it will be the winner.

Anybody have tricks for the Bigma?

It appears that the K3's sensor is able to get more out of the superior Tamron optics then the extra Bigma reach... Something given the price difference!

However, love the build quality of the Bigma compared to the Tamron.

Sorry to ramble on so much - just a little surprised...

[jatrax]

With the Tamron you are shooting @ 200mm with the Bigma you are shooting @ 450mm. I know that is obvious but there is a huge difference in getting a sharp image with a 450mm lens. Things that don't make much difference @ 200mm start to become issues. Mirror slap, wind vibrations, and so on.

I have no experience with the Tamron so I have no idea whether your results are typical. Just make sure you have other factors controlled. For example you should have no issues shooting @ 1/200th with the Tamron. With the Bigma you will need to be 1/500th or faster.

[GaryH]

I had very good results with the Bigma . For me, I got best results on a stout monopod and used OS with SR off. The Bigma is generally a decent lens. I sold mine because I am not doing as much wildlife these days and the HD 1.4x paired with the DA* 60-250 and DA* 300 fill any needs I have for a longer lens.

[SaltyPentax]

Ok. SR off. Might have missed that one. Gary, how did you find the 60-250 with the HD converter compared to your Bigma?

Thanks!

[DeadJohn]

I have the same OS HSM 50-500 as you. I am very happy with my copy. When I was shopping, some PF members said it was unsharp at the long end, but I think that may have applied more to older models. These shots are all taken with a Pentax K-5.

410mm plus a later minor crop for composition. This was across water on a very windy day, so atmospheric distortion is evident especially in the lower potion, but the top of the lighthouse shows sharp, fine lines. It was so windy that I used a tripod plus optical stabilization.


Handheld with OS in panning mode.


Handheld, then around 1/2 of the pixels cropped away to remove distracting OOF power lines and branches.

[SaltyPentax]

DeadJohn. Nice shots! I'd like to love my Bigma. I'll keep playing with it. I know my SR was not off so maybe that will help some. Do you use in TAv? If so, what are your target shutter speeds?

[redpit]

DeadJohn. Nice shots! I'd like to love my Bigma. I'll keep playing with it. I know my SR was not off so maybe that will help some. Do you use in TAv? If so, what are your target shutter speeds?

Look no further my friend. You have to keep SR off on Bigma! Otherwise pics are shaky and blurred! I have both lenses so I know you'll love Bigma too!

[kiwi_jono]

The SR indeed sounds like the culprit.
That said I have been amazed by how sharp my Tamron (especially at the 200mm end). Normally people steer clear of doublers but for fun I tried one on my Tammy. With the doubler I found I can get better detail than cropping from 200mm and it significantly out resolves my Soligor 400. I would use the doubler more but the Tammy does not AF properly with it and the Tammy is not nice to manual focus unfortunately.

[crewl1]

The Tamron is a sharp lens with only a 3x zoom range and is of a higher lens class with its constant f2.8 design. You can't expect that type of IQ from a variable aperture 10x zoom.

In my testing the Bigma works best if shot shorter than 500mm and you make whatever technique adjustments are needed for handling a long heavy lens. f8 or thereabouts is its sharpest aperture.

The Sigma OS system works in your favor vs the Pentax SR for this lens so use it when you can. (note it will drain your batteries faster so keep some spares.)

Once you get the hang of the Bigma it will yield great results.

For me the Bigma has its use in outdoor sports and casual wildlife shooting. If I want best quality long lens I prefer the DA*300 with the HD 1.4x for a resulting 420mm system.

[DeadJohn]

DeadJohn. Nice shots! I'd like to love my Bigma. I'll keep playing with it. I know my SR was not off so maybe that will help some. Do you use in TAv? If so, what are your target shutter speeds?

I use Av or TAv most of the time. I start with Av at f8. That usually results in shutter speeds that are fast enough when OS can be used.

TAv is good when it's cloudy and Av gives shutter speeds that seem too slow. TAv is also good for birds in flight because OS isn't usable when moving erratically (OS has a pan mode but that's only good for more predictable movement than birds).

I also use TAv or Tv when I want a slow shutter. Things like panning on a moving car to smear the background or showing rotor movement on a helicopter.

[Lowell Goudge]

I can only repeat here what some others have posted in the past. Some variants of the BIGMA are a little soft as you approach 500mm. So with that in mind, in some ways it is not a surprise to see a comment that a 70-200/2.8 out perform as a BIGMA, even when considering the crop.

Remember though you have more light to work with, with a 70-200/2.8. So maybe try stopping down to an equal aperture with the shorter lens, so you shoot the same shutter speed.

Maybe your sharpness is more to do with shooting conditions than the lens itself

[CypherOz]

The original 50-500 Bigma.



Camera Maker: RICOH IMAGING COMPANY, LTD.
Camera Model: PENTAX K-3
Lens: Sigma Lens
Image Date: 2015-04-15 11:56:51 +0000
Focal Length: 420mm (35mm equivalent: 630mm)
Aperture: ƒ/8.0
Exposure Time: 0.0010 s (1/1000)
ISO equiv: 800
Exposure Bias: none
Metering Mode: Center Weight
Exposure: aperture priority (semi-auto)
White Balance: Manual
Flash Fired: No (enforced)

[audiobomber]

With the Tamron you are shooting @ 200mm with the Bigma you are shooting @ 450mm. I know that is obvious but there is a huge difference in getting a sharp image with a 450mm lens. Things that don't make much difference @ 200mm start to become issues. Mirror slap, wind vibrations, and so on.

The rule of thumb for handheld images is 1/(Effective FL). For a sharp shot at 200mm, and cropped to 450mm FOV as the OP describes, you need the same shutter speed as if you shot at 450mm (1/750 second).

[SaltyPentax]

Thanks for all the great tips - they certainly made a difference. However, after a brief stint of excessive LBA - culminating in a 60-250 and 1.4 HD converter, I must say the pentax is very much the winner. The Bigma suffered not so much from definition degradation but more from a blurred glow on contrasty edges. Pixels in low contrast to their surrounding pixels were very clear, ones in high contrast situations developed a glowing blur that was noticeably absent in the 60-250 and HD converter. Without the converter, the Pentax could not keep up with the Bigma (when cropped to match a 400mm Bigma image). The Bigma at 400 and cropped to match the Bigma at 500mm was superior (ie the Bigma softened significantly past 400).

So, based on my semi-scientific testing, I can't sing enough praise for the 60-250 AND the HD converter. I previously owned the pentax but not the converter, I was never blown away by it... But matched with the converter - awesome! And Weather sealed!

+1 Pentax!