Pentax at 400

It's never a good thing when I start thinking about "improving" my Pentax kit, invariably it costs me money - but my view is I can usually get most of it back by re-selling some of the replaced items (or the newly acquired items if they don't do the job).

My latest venture is to replace my FA*400/5.6 and F*300/4.5 with the highly acclaimed HD Pentax DFA 150mm-450mm - so I found one and promptly purchased it (from the proceeds of recent sales). The theory is that when I next visit Brownsea Island I can use it as my sole squirrelling/birding/deering/shipping/aeroplaneing lens!

There should be many advantages and only a few disadvantages - the flexibility of the zoom being the first advantage, a pretty good wildlife range 150-450. The latest coatings and a relatively new optical design being the second - providing better IQ and better flare resistance. All-Weather design is another plus point (I usually visit in Autumn so there's a reasonable chance of rain).
The disadvantages - well there aren't many - I can only really think of the size and weight. Maximum aperture is the same as my FA*400 so no difference there,

Anyway, as I haven't sold my FA*400mm yet I thought I'd do some back garden shooting to see how the 400 stacks up against the mighty 150-450 - theoretically there should be no contest! The FA* is nearly 20 years older, and optical design has advanced quite a bit - so how much difference could there be?

Take a look for yourself - these are all "paired up", each images taken with the same shutter and aperture as each other (TAV mode, so there could be minor discrepancy in ISO) - no editing, raw converted to jpeg for output via LightRoom. Click on the image to see them at 2048 pixels (to get a better impression).

F5.6 at 1/500
DFA


FA*



F5.6 at 1/500
DFA


FA*



F5.6 at 1/500
DFA


FA*



F11 at 1/500
DFA


FA*



F11 at 1/500 (this pair had the exposure increased by 1.5 stops to improve the detail)
DFA


FA*



Is there any difference? Yes, some - but not a great deal. The FA* does tend to "purple fringe" in some situations. The FA* can be slightly softer looking on some shots (not in a bad way IMO). But in terms of detail and overall sharpness there isn't a lot in it.

Based on these results I won't be parting with the FA* anytime soon - it is half the weight of the DFA zoom and it's more compact (fits in more compartments of the bags). I might change my mind after my next Brownsea trip - that'll prove how well it works in lower light, but let's wait and see

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Oh - one other thing to note! The DFA shots were taken at the marked "400mm" setting on the barrel of the lens but the lens data shows this as "410mm" - but these images appear to be a slightly lesser magnification than the FA* equivalents I did take a few at 450mm to compare, illustrated by this pair below (the lighting had changed significantly between shots, so I would only use the magnification as a guide on these).

DFA @ 450mm



FA*400



So - the FA* magnification isn't far of the long end (450mm) of the DFA

Hope that's been of value or interest to someone

Ah! So that's the reason for the recent activity in the classifieds .

Personally, I'd consider both lenses to be perfectly acceptable and decide which lens to have in the bag based on non-optical criteria (zoom or not, size, weight, handling etc.). But then I don't pixel peep and don't think that a sharper lens is necessarily a better or more desirable lens.

Could the FA* magnification being close to the long end (450mm) of the DFA be due to focus breathing in the latter? That gin bottle is presumably a lot closer than infinity (within a reasonable drinking distance :wink). Would a fairer comparison be something at distances typical of squirrels/birds/deer/ships/aeroplanes?

Steve

I think the biggest difference will be on your wallet.

I think you've nailed it Steve - Focus Breathing - and I did have that in the back of my mind, but in practical use I suspect these lenses are used at much closer distances than infinity most of the time, so the real test will be in the wild I'll report back once I've done my next Brownsea Island trip. The Deer and Birds will be at the greatest distances, the squirrels will be the closest (hopefully) - I think I know the outcome in terms of which lenses I retain (Big Clue - "All of them"!).

I really did expect to find the new HD DFA 150-450 to be notably superior in IQ (especially at Maximum aperture) but the FA*400 really does hold its own