Originally posted by ogl Like 900 mm or like 600 mm? Only at f4.5?
It's rather strange way to get picture with 600 (900) mm lens resolution:
To buy Pentax Q for USD800 + Q-K adapter for some USD (I think USD200) and then buy DA*300/4 for USD1300....
Wow...it's outstanding. To spend more than USD2000 for make some shots at 1680 mm (without AF!!!) at f4.5 in very good sunny weather at ISO125 with exposure limit 1/2000 .
Don't forget about ISO and exposure (1/2000 only), please. I doubt that It will give any good IQ at ISO above 200.
Oh please! $2K is cheap when you're talking reach of over 600mm (ever priced even a used FA* 600/4 or an FA* 250-600/5.6?), and the whole Q, K>Q adapter, plus a 300/4 lens would weigh about 3 lbs and fit in a relatively normal bag. Anyway, I already have all the long glass that I need, and I assume that most who would want to use a Q for the crop factor advantage would also, so the price is back at $800 RRP, or maybe $1K with the adapter. Considering that I already have more than the whole Q system invested in a number of individual lenses each, not to mention the gear needed to support them, I find the Q offers the potential to expand my ability to shoot long to an extent that the cost is easily justifiable. Even if it doesn't work as well as anticipated, I still have a tiny quality camera that I can carry on a day to day basis, and it has the versatility with interchangeable lenses that has previously stopped me from buying any of the existing advanced compacts.
A Q with a K>Q adapter would be a pocketable 3.6x TC (compared to APS-C) that doesn't cost 3.6 stops in exposure. Before you start quoting the DOF EQ conversions, I actually welcome the deeper DOF since I usually shoot at relatively short subject distances, and the DOF of fast ultra teles at short distances is very narrow -- too narrow actually. Also, DR is not much of a concern for me since I shoot jpegs with my DSLRs, and my output medium is normally prints, so this has never been a priority consideration for me.
The DA* would cause some difficulty with controlling the aperture since it doesn't have an aperture ring, but perhaps that's what the scale engraved on the prototype K>Q adapter are for -- controlling the aperture in DA lenses, or any A capable lens for that matter -- not too much of a stretch since it would only have to be a mechanical linkage, and 7 steps would be adequate for just about any lens. I don't think that the scale indicates an aperture diaphragm in the adapter since I doubt if it could be placed to accurately block the same amount of light for every FL at a given setting since the light path is narrower at a given distance behind the lens for teles vs wide angles. This is irrelevant to me since I'd use an FA* 300/4.5 or FA* 300/2.8, and they have aperture rings.
IQ when shooting long is always a trade off. Shooting very long (600mm or longer) at f4-5,6 is only possible in APS-C with 13 lb + lenses that cost in the neighborhood of $6K and have MFDs of 4m or more. Use anything shorter, and you'd need to:
1. Get closer, which is not always possible,
2. Crop, which robs resolution, or
3. Use a TC, which robs light.
Higher shutter speeds are obviously an important component of this type of shooting as camera shake (even when tripod mounted) is exaggerated by the narrow AOV and relative subject magnification (there are always subject motion concerns also), so being able to use a wider aperture is a definite virtue to keep shutter speeds up.
At longer distances, support becomes increasingly important. With the light weight of the Q body, and the ability to use the more convenient f4 class lenses, a 3 lb CF tripod and a ball head can suffice where a 7-9 lb CF tripod and a gimbal are really needed to conveniently use the fastest long glass. These would not only be lighter, but would cost significantly less. Another possible plus for the Q tele shooter.
The only possible downside that I see with the Q + K>Q adapter (other than possible performance quirks) is the electronic shutter, but we don't really know how it will perform, and even this might be a trade-off -- zero vibration vs some degree of IQ degradation. For me, it's worth a try. . .
I'd personally choose to shoot faster apertures and higher shutter speeds and sacrifice whatever degree of IQ is lost from using the smaller sensor. Judging from the samples I've seen, the IQ differential between the small sensor and any of my DLSR bodies is not nearly as detracting as a blurred capture. For bird shoots, I'd still primarily use the DSLR for the OVF, and the Q would be an accessory that I'd use like a TC for extra reach if needed. I would also anticipate using it for lightweight walk around birding handheld, as well as macros where the Q would also offer some significant advantages.
Scott