Snap focus vs AF at same shutter speed

[Kimoi]

Hi everybody,

I bought last month a GRD 4. So far I really enjoy it and still learn how to use it optimal conditions. Currently I am a bit puzzled about the use of the snap function and the difference with AF in particular situations.

Indeed, when I take a picture in a dark place of - let say - a door handle while walking with Snap focus and shutter speed at 1/60, the handle is in focus. Not razor sharp but it is ok. When I take the same exact picture with AF at 1/60 while walking and pressing fully the shutter button (I guess it doesn't really have time to focus), the image is really blurry. Not really out of focus but rather if the shutter speed was much slower that 1/60 (the handle has a kind of light drag). However it displays 1/60.

So I was wondering why this difference?

Is AF adding an extra shutter lag in top of the shutter speed without saying it?

Maybe, this is not fundamental but I am still thinking about the real advantages of snap over AF in practice... Indeed, I don't really find my pictures taken with Snap focus super sharp and I am wondering if taking them with AF will not lead to the same result on a small sensor like the GRD4 with a wide angle.

Thanks for any comments!!!

 

[Blow-in]

I think my first comment is that if you are walking, 1/60th could be too slow a shutter speed - especially for objects relatively close to you - and it could simply be the motion causing a blur. Secondly, while using AF in low light you could try enabling the AF auxilary light (in the set-up menu).

Regarding snap, you have several options in the shooting menu (snap focus distance) and you need to select the distance appropriate to the shot...if you choose auto the camera selects the distance using the hybrid AF external sensor (I think)...I'm not sure how effective this will be in low light. Usefully you can assign the snap options to FN1 or 2.

Snap is really there for a quick opportunity when AF is too slow...if you have time you may prefer to use AF...in either case, a small aperture will increase the depth of focus..but also give you a slower shutter speed.

I hope this is of some small help. There are loads of options with the GRD IV and I'm still exploring them too.

Richard

 

[odklizec]

Hi Kimoi and welcome here! I agree with what Richard already suggested. 1/60 is too slow for walk/people in motion.

Just one additional thing. You mentioned this in your description:

When I take the same exact picture with AF at 1/60 while walking and pressing fully the shutter button (I guess it doesn't really have time to focus), the image is really blurry.

Do you mean you pressed the shutter without the half-press stage? I mean, you fully pressed the shutter without waiting for the AF lock? Then I guess your GRD has enabled "Full Press Snap" option? This option, if enabled, automatically switch the camera from the AF mode to Snap mode (on full shutter press without half press stage). And because your actual Snap mode distance was most probably much different from the actual subject distance, the photo has become blurry? Just examine your actual Full Press Snap setting

 

[Kimoi]

Hi everyone,

thanks a lot for your kind answers. I think learning how to use the GRD in an optimal way is a long journey For the AF, I disabled the full press snap option and just fully press the shutter button without giving the time to AF to lock the subjetc- which is stupid I know Anyway, I was just surprised to get a blurry image with the same shutter speed. But maybe my hands were shaking a little bit more when I took the picture with AF. I will try a faster shutter speed.

I have also a second question about the metering of the snap focus. I try almost all of them 1,1.5, 2.5 etc at full aperture with an object at 1meter from me and doesn't notice a huge difference. The contour of the object are always a bit soft... However when I use the AF with the same aperture, the contour are really sharp. Is it because, the snap is too approximative at full aperture with a very narrow DOF? Indeed, for smaller aperture like f4.5 it becomes much sharper.

So my question is: do some of you use snap mode at full aperture and obtain sharp subjects? Or does the snap mode makes sense only if you close the aperture? In this case what are your usual settings?

I don't really care about having sharp or soft images but I care about knowing the limitations of the camera


Thanks!