Pentax-DA 560mm F5.6 ED AW

Started Mar 28, 2013 | Discussions thread
viking79 Forum Pro • Posts: 14,149
Re: Pentax-DA 560mm F5.6 ED AW

awaldram wrote:

Tom Lusk wrote:

Hi Eric:

Looks like I was confused by the wording.

I'm with you on the "equivalent" deal.

Whenever I read that someone needs more "reach", so prefers not to use a full frame camera with the same size lens, I shake my head.

Given pixel density and sensor size the statement holds water.

You need a 36mp FF to achieve the same 'reach' as a 16mp aps-c with the same lens @ the same resolution.

This lens appears to be a non-starter for me.

My Sigma 500 doesn't require using f8-11 for maximum sharpness, which is a good thing since I rarely get good enough light to shoot such apertures and maintain an appropriate shutter speed.

You must have a special version then, The only lens I've ever come across that isn't at peak 1-2 stops down form max aperture is the da 40 Limited a unique trait of that one lens.

If a lens peaks at diffraction limit, that is not a good thing. That means it is aberration limited before that.  Yes, most lenses peak 1-4 stops down, unless it is already near diffraction limit wide open (some Q lenses), or like you say, some lenses are just good wide open (this is good).

Looking at the samples for the 560 on their review site, f/8 is definitely better than f/16 in the center, but not sure that f/8 is better than f/11?  At f/11 it is definitely diffraction limited, so the lens doesn't appear to be performing that well if it is peaking at diffraction limit for f/11.  Most APS-C lenses should peak around f/6.3-7.1. It does look decent at f/8.

Any lens is about at the "minimum decency level" at f/16 on APS-C, f/22 on almost any lens is too soft, and f/5.6 looks about like f/16.  That isn't great, that is saying the lens is barely decent at f/5.6, but it isn't unusual for a lens to perform about as well wide open as at f/16, although I would hope for better from such a "slow" lens.

The CA as exhibited in some of the sample shots would be a pain and, as I don't use a tripod, the comment about the balance of the lens is discouraging.

Sigma are the masters of CA control whereas Pentax always are weak in this area.

Maybe too general of a statement.  I have seen plenty bad CA from Sigma lenses.

I think they'll have to drop the price significantly, in order to get a decent amount of sales.

No price will achieve decent sales they can sell 1 or 2 @$7000 or 1 or 2 @$5000 it already at the low end for an OEM telephoto, to low and its into the 3rd party range so would lose all the prestige buyers.

It's a niche product and not price critical.

Exactly, they probably don't plan on selling a lot of them.

As someone said, I would expect to see some BIF shots etc from a lens such as this.  Sort of defeats the purpose of the review.  Test charts are certainly too close for this lens to be at its optimum, and even the cactus might be too close too.  Don't know how far away it is.


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