[Stavri]

Being bit by the pixelpeeping bug (with some free time on my hands this saturday) I decided to do a comparison between my Sigma EX DG 70-200mm f2.8 HSM II and DA* 60-250mm on K10D. The issues with focus breathing of the Da* 60-250 are well known, but its still jarring to see it when compared to other telephoto lenses.

Pentax K10D on tripod: 2s delay shutter, 6 feet away from the subject:
Sigma @ 200mm vs Pentax @ 250mm


Sharpness test @ 200mm & 250mm


IMO the sharpness between the two lenses is very close, the DA* exhibiting more contrast out of camera (and can be achieved on the Sigma with a few slider adjustments) The Sigma is also significantly brighter/ by 1/3-1/2 stop IMO. Correction: The shots with DA* are underexposed by 1/2 stop. the Sigma and Da should have similar transmittance.

I put the sigma on the marketplace some days back, shame I cannot keep them both.
Sigma EX DG 70-200 F2.8 HSM II for Pentax - PentaxForums.com

---

Last edited by Stavri; 11-04-2017 at 02:11 PM.

[dave2k]

Maybe I'm missing something, but the subject of the photos appears to be bigger for the Sigma at 200 than the Pentax at 250. I would expect it to be the other way around even if the Pentax 250 isn't really 250. I have both of these lenses and I find that the 60-250 has superior IQ in most situations, especially with regard to sharpness. I keep the Sigma for low light sports and pretty much use the Pentax for everything else within this focal range.

[HarisF1]

Maybe I'm missing something, but the subject of the photos appears to be bigger for the Sigma at 200 than the Pentax at 250. I would expect it to be the other way around even if the Pentax 250 isn't really 250. I have both of these lenses and I find that the 60-250 has superior IQ in most situations, especially with regard to sharpness. I keep the Sigma for low light sports and pretty much use the Pentax for everything else within this focal range.

Focus breathing!

[dave2k]

Focus breathing!

From 250 to significantly lower than 200? That seems like a lot!

[Stavri]

From 250 to significantly lower than 200? That seems like a lot!

The 60-250 focus breathing is well know, and talked about topic here at PF, users have reported anything from as low as 140mm up to its specified 250mm focal length. I would recommend that you do a quick test yourself, comparing the 60-250 to your other telelephoto lenses.

[Adam]

The closer the subject, the shorter the EFL will be at the 250mm setting. The Pentax shots do appear underexposed- did you fix the shutter speed?

[dave2k]

Ok, I'm fully convinced now. I did two tests, one with the subject at about 100 yards and one at about 7 feet. The long range outcome was exactly as I expected, the 250 FOV was significantly smaller than that of the 200. At short range the focus breathing was apparent and the 250 had a greater FOV than the 200. I knew about this issue but not the degree to which is impacts the FOV. I very rarely use my telephoto lenses for close subjects so that is probably why I never noticed how strong the effect can be. This forum is a great place for learning things without actually stumbling upon them in real life.

[UncleVanya]

For the 60-250 at under 10m it is closer to a 135mm FOV. The closer the worse it is.

[Stavri]

The closer the subject, the shorter the EFL will be at the 250mm setting. The Pentax shots do appear underexposed- did you fix the shutter speed?

You're right Adam, the change in exposure was due to user error... the lenses should have similar transmittance..

[aiki76]

likely It has been already discussed, so excuse me in advance, but what is the performance (both optically and from the AF side) of the 60 250 with the Pentax teleconverters (the new HD and the old F-AF 1.7x)?
And that of the Sigma? Thanks

[UncleVanya]

likely It has been already discussed, so excuse me in advance, but what is the performance (both optically and from the AF side) of the 60 250 with the Pentax teleconverters (the new HD and the old F-AF 1.7x)?
And that of the Sigma? Thanks

Can't say for the Sigma, but at f2.8 before the TC it is potentially more practical. I have used both the HD 1.4x and F 1.7x on my 60-250 with good optical results.

[aiki76]

Can't say for the Sigma, but at f2.8 before the TC it is potentially more practical. I have used both the HD 1.4x and F 1.7x on my 60-250 with good optical results.

What about the AF? Thanks

[UncleVanya]

What about the AF? Thanks

Either TC on the 60-250 in good light worked just fine. The problem is going to be in poor light, since the lens will be an f 5.6 or f 6.8, but in bright sunlight I never noticed any hesitancy or inaccuracy.