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10-03-2015, 06:17 PM - 1 Like   #1
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400mm challenge FA*250-600 and much cheaper competitors

Here I have taken the opportunity to compare four lenses at the 400mm focal length. There are:

Flexar 400/6.3 - A very cheap T2 mount lens (adapted to K mount) with preset aperture but 10+ blades. Super super light and small when compared to the three other lenses. Perhaps $50-100 lens

SMC Pentax 'K' 400/5.6 - The next most expensive lens in the comparison. Larger and heavier than the Flexar. Fewer aperture blades. Not preset, green button metering needed. Recently CLA'd by Eric so in great condition. Perhaps $300 lens

Sigma 150-500/5.6-6.3 - moderately expensive zoom recently discontinued. Has built in optical stabilisation heaviest lens but well balanced in hand with camera and tripod foot/ handle. Perhaps a $900 lens

SMC Pentax FA* 250-600/5.6 - a very expensive zoom discontinued about 15 years ago.

Now, this challenge is exactly that, a challenge, not a scientific test. But, in the interests of making it comparable, I eliminated as many variables as possible viz.:

1. used tripod
2. turned stabilisers and shake reduction off
3. shot wide open then at f10 for each lens
4. all shot with one camera and in quick succession (K3)
5. shot with 2 second delay to reduce camera shake
6. shot in Av for flexor and M for all other lenses (green button metering)

First up, wide open shots aimed at a target about 60 metres away

FA*250-600 @5.6

Sigma 150-500 @6.3

SMC Pentax 400/5.6 @5.6

Flexar 400/6.3 @6.3

FA*250-600 @510

Sigma 150-500 @10

SMC Pentax 400/5.6 @10

Flexar 400/6.3 @10

Now shots taken at or near shortest focusing distance

FA*250-600 @5.6
shortest focusing distance is 3.5m

Sigma 150-500 @6.3
shortest focusing distance is 2m

SMC Pentax 400/5.6 @5.6
shortest focusing distance is 7.5m

Flexar 400/6.3 @6.3
shortest focusing distance is 6.5m

Now for shots at shortest focus distance but at f10

FA*250-600 @5.6

Sigma 150-500 @10

SMC Pentax 400/5.6 @10

Flexar 400/6.3 @10

---------- Post added 10-04-15 at 12:31 PM ----------

My thoughts:

The FA*250-600 is the winner in the challenge, closely followed by Sigma 150-500. Not much in it between these two lenses. Colours and sharpness better in the FA*250-600. Handling and cost in favour of the Sigma 150-500.

But, the surprise performer is the really cheap Flexar. If handles CAs much better than the compare fully manual SMC Pentax 400/5.6. Colours are better in the SMC Pentax 400/5.6 with the Flexar showing less contrast. However, in the digital world, post processing can largely over come this issue. I think the SMC Pentax 400/5.6 is sharper, but not by much. The Flexar surprisingly has a shorter minimum focusing distance of 6.5m compared to 7.5m

So, if you are on a really low budget and can do post processing, the clear winner here is the Flexar 400/6.3. Reasonably good sharpness, correctable contrast, sharp enough and super light. Can be used in AV mode, whereas the SMC Pentax 40/5.6 requires green button metering.

If you aspire to get the FA* 250-600/5.6 and can't afford, then don't despair. The Sigma 150-500 is really quite good by comparison. Its 2m minimum focus distance makes this lens really versatile as does the weight. Focusing is fast and silent. But, for critical sharpness, the FA* 250-600/5.6 is superior (and only gets bette through to 500mm).

Anyway, happy to hear what others think.

Last edited by Wild Mark; 10-03-2015 at 06:34 PM. Reason: error correction
10-03-2015, 08:26 PM   #2
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Cool! Why don't PENTAX make newSMC Pentax HD or SMC D FA* 250-600/1.8??? Would it cost $200,000???
10-03-2015, 09:31 PM   #3

Join Date: Sep 2011
Location: Richland, Washington, USA
Posts: 886
QuoteOriginally posted by KDD Quote
Cool! Why don't PENTAX make newSMC Pentax HD or SMC D FA* 250-600/1.8??? Would it cost $200,000???
I hate to think what a 250-600 f1.8 lens would weigh. The 250-600 f5.6 is plenty heavy enough.

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