[Frogfish]

Recent debates on the virtues or otherwise of certain lense & TC combinations had me resolve to at least check what I have to hand - I need to know, when I go birding in particular, what is going to give me the best results (even though I don't shoot on a tripod very often). This was not designed to be a scientifically perfect test - only to give me real world results under real world conditions.

Methodology
K5 on a tripod + ball head, Manual Exposure (1/250, f8, ISO 200), timer : 2 second delay, SR off, AWB, AF-S, Spot Focus, Centre Weighted Metering. AF or MF (when AF unable to lock focus) : Shot taken on camera focus confirmation (beep).
2 shots per lense per combination - best shot selected, inferior shot deleted.
Subject was a broken white plant pot with blue floral design placed at 15 metres (ca. 16.5 yards or 50 feet).
Note - the camera will not display the exact f stop for some lenses with TCs attached (when the minimum exceeds f8) so you can calculate the exact stop yourselves from the camera max f stop + TCs. I don't find this particularly relevant for two reasons :
a) you can't reduce this minimum f stop for the lense + TC combination
b) I wouldn't be using faster lenses at those smaller apertures.

Post Processing
Auto Curves all shots to make viewing easier for darker shots.
Resizing for upload to online storage (1250 x 1080) + Forum compression.

Conditions
Bright but overcast. Sun directly behind the tripod (early afternoon). No wind. Sheltered garden. Dog was not permitted to chew, bury or otherwise molest the photographic equipment. A cup of tea was consumer after 1 hour. No toilet breaks.

Lenses Used.
S150 = Sigma 50-150 / f2.8 (this was the lense currently on the camera so I added it to the test anyway) @ 150mm
F210 = Pentax F 70-210 / f4 - f5.6 @210
DA55300 = Pentax DA 55-300 / f4 - f5.8 @300
*300 = Pentax DA*300 / f4
T500 = Tamron BB 500 Mirror / f8
SMC300 = SMC Takumar 300 / f4 - NB. No TC shots taken as I didn't want to risk the adapter getting stuck on one of them ! Also note an error in exposure settings (mistakenly f6.3 instead of f8).

Teleconverters Used.
P17 = Pentax AFA x1.7
T14 = Tamron Pz x1.4

Combinations Tested.
S150 (no TC) (+T14) (+P17) - NB. Stacked TCs unresponsive so no shot taken.
F210 (no TC) (+T14) (+P17) (T14+P17)
DA55300 (no TC) (+T14) (+P17) (T14+P17) - NB. Focus lock achieved with P17 only 1 in 5 attempts. MF used for T14+P17 as no focus lock could be achieved in AF.
*300 (no TC) (+T14) (+P17) (T14+P17)
T500 (no TC) (+T14) (+P17) - NB. Stacked TCs - focus lock unresponsive so no shot taken.
Various 300mm @ 100%
Various 500mm @ 100%
Various 700mm @ 100%

Draw your own conclusions !
____________________________











@300mm



@500mm



@700mm

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Last edited by Frogfish; 04-10-2011 at 05:25 AM.

[normhead]

The Tamron 1.4 looks like the way to go for IQ.

[JohnBee]

Wow great test!!!
I've been meaning to do the same thing for sometime now, but I just couldn't get around to it.

One thing that came to mind when I was looking over your results(please don't take offense), is where you might have been better off moving the subject distance to compensate as you're focal length increased. This way, the objective might be easier to interpret against the extra magnification. (or something along those lines). If that makes any sense.

Anyways, thanks a great deal for doing this.
I've owned the 300* but got rid of it because I didn't use it enough.
Not I guess I'm just going to have to get another one!

PS. Oh and how about that Tamron BB mirror eh! If it wasn't for those #^$@)$&* highlight donuts, that lens would be a star among stars! - But I couldn't seem to ever get passed the OOF rendering of that lens.

[dadipentak]

Thanks, Kevin--pretty interesting. Confirms my good experience with the DA*300 & 1.7x TC (as well as my aversion to TC stacking ;~) Some (less rigorous) tests I've done recently also confirm my impression that the DA*300 & 2x-S work very well together.

[Clinton]

Nice test Kevin. It looks from the first shot as though the 1.7 afa was overexposed, but I'm not sure the detail was all that different from the tamron.

Were you using the latest K5 firmware?

Are you using the latest firmware? Did you use regular AF, or live view AF? Also, did you set spot metering and single point AF to avoid any AF/Exposure changes between tests?

[Frogfish]

Normhead - I think both the x1.4 and x1.7 performed admirably. We have to take into consideration that the x1.7 has almost twice the magnification of the x1.4.

Thanks John ! No offence taken at all. I mentioned that this test was primarily for birds - so getting closer than 15m to compensate wouldn't work in the real (birding) world. The DA*300 is a downright unbelievable lense. TBH I hardly ever notice the doughnuts that can appear in certain mirror shots - so the Tamron BB500 gets a big thumbs up from me ! US$100+ and the smoothest focusing ring on any lense I've ever had in my hands ? Massive !

Thanks Dave ! I know of at least a couple of guys who stack exactly that combo on the *300 - they must have the patience of saints though !

Thank you Clinton - yes I have the latest K5 firmware installed. I was using regular AF / Spot focus and Centre Weighted Metering. However exposure was fully manual.

[Lowell Goudge]

while an interesting comparison, I think there are 2 areas that detract from the presentation

first, you do not maintain the image magnification on all shots, therefore you are not always comparing apples to apples.

and

Second, the exposure is all over the place, with some examples burned out to the point that this detracts from the IQ.

[Frogfish]

while an interesting comparison, I think there are 2 areas that detract from the presentation

first, you do not maintain the image magnification on all shots, therefore you are not always comparing apples to apples.

and

Second, the exposure is all over the place, with some examples burned out to the point that this detracts from the IQ.

Thanks for commenting Lowell.

re. Image Magnification. - I'm not a 100% with your meaning on this. The idea was to show 1:1 on all shots. Which was the case in the various lenses with different TC combinations attached. Whilst on the 300/500/700 comparisons the idea was to compare the IQ at that specific FL or as close to it as I could get, to give some idea of which combination would give the best IQ for that FL. Sometimes that meant slightly higher or lower magnification than 100%.

Exposure : I used set exposure parameters so that direct comparisons of sharpness could be made - the one which is burnt out is the only shot taken with the Tak 300/4 - I should probably have excluded it really as I forgot to change the aperture from f6.3 to f8 (as I mentioned above) - hence the result.

The test is really only to check the sharpness that can be expected from each combination.

[Lowell Goudge]

Thanks for commenting Lowell.

re. Image Magnification. - I'm not a 100% with your meaning on this. The idea was to show 1:1 on all shots. Which was the case in the various lenses with different TC combinations attached. Whilst on the 300/500/700 comparisons the idea was to compare the IQ at that specific FL or as close to it as I could get, to give some idea of which combination would give the best IQ for that FL. Sometimes that meant slightly higher or lower magnification than 100%.

I think for a user, it might be more relevant to show the same overall magnification i.e. image size for each combo. I assumed this was what you tried to do with the sigma 50-150 for example, eg, is cropping better than a 2x TC? If you gave the same image size, with each combo, then there would be a direct 1:1 for comparison. I rais this point because many times, we have the discussion that cropping in is better than adding a TC, which may not be the case

Exposure : I used set exposure parameters so that direct comparisons of sharpness could be made - the one which is burnt out is the only shot taken with the Tak 300/4 - I should probably have excluded it really as I forgot to change the aperture from f6.3 to f8 (as I mentioned above) - hence the result.

The test is really only to check the sharpness that can be expected from each combination.

While the test was to check sharpness, the "impression" of sharpness depends highly on contrast and exposure as well.

I think if the shots all had the same exposure value (i.e. grey scale value) on the blue detail for example, it would give a different impression of sharpness. Same goes for the final image magnification, it is hard to really compare sharpness when the image size is different.

Overall, these are small points,

[audiobomber]

Excellent series froggy! I liked the format a lot. I should stop procrastinating and buy the DA*300.

[dadipentak]

I should stop procrastinating and buy the DA*300.

I admire your ability to procrastinate on lens acquisitions.

[Frogfish]

Excellent series froggy! I liked the format a lot. I should stop procrastinating and buy the DA*300.

Thanks AD !

Thank you Lowell for the clarification.

[Clinton]

I admire your ability to procrastinate on lens acquisitions.

I agree. Nice work on your ability to procrastinate the purchase.

[audiobomber]

I agree. Nice work on your ability to procrastinate the purchase.

I had one in my shopping cart this morning but I managed to procrastinate it away. I got the 18-135, even though I said I'm done with superzooms. I need a plan.

[dadipentak]

I had one in my shopping cart this morning but I managed to procrastinate it away. I got the 18-135, even though I said I'm done with superzooms.

DOH!