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6d w/ 105mm how far can I "zoom" in for pseudo 300mm shots?


I've just ordered my first dslr, a 6d with the 24-105 L lens. I've had digital point and shoots before but my last SLR was a film camera so I'm unsure of the IQ of a nice dslr.


I generally use a 300mm lens a lot, but since I just dropped almost $2800 dollars on this new setup, I really don't want to spend another grand (at least) on a longer L lens at this time. Thing is, I'm going on a nice vacation in a couple of weeks and I know that I'll be missing a longer lens.


So I thought that maybe if I just shoot with the 105 focused to "infinity" and then crop and zoom in on the finished image, I could have the effect of a longer lens without actually having the longer lens. Will that actually work? Will the image quality be good enough for that to work? Will the images be sharp and focused with this technique? I know there are a lot of variables such as available light, ISO, etc. I don't plan to blow any of these photos up very large--most of them will be snapshots on the computer but if I take some really exceptional ones they could become wall art.


Or is this a dumb idea and I should buy a longer lens?

Which leads to part 2:

If I should buy a longer lens, having never show with an L lens before and hearing that they're awesome, would I be really disappointed if I got a non-L longer lens. Would I see a ton of difference in IQ, given that nearly all will be seen just on the computer and maybe only a few blown up larger?


I also thought about maybe getting an extender as a less expensive option but they don't list this lens as being compatible.


I know this is a bit long winded but thanks for any help you can offer!


Rising Star

@Brad wrote:


tree bark - mraw (11mb), 1/60, f4, 1250 ISO, full zoom on 24-105 L, 100% blowup

Probably blurry due to handheld shake.  The "1/(focal length)" rule might be helpful:


@Brad wrote:
christmas - full raw (24mb), 1/30, f4, 400 ISO, full wide on 24-105 L, 100% blowup, on tripod and 2 second shutter delay to eliminate shake

 It seems to me that nothing is very sharp unless there's a lot of light, more specifically sunlight, because in the christmas shot it was fairly bright in the house even though it was evening. I'd say there was a good 800-1000 watts of lights on in the room.

Indoors needs a lot of light.  I've never shot film, so can't say whether this is different than what you're used to, but indoors at f/4 (I also use a 24-105mm) needs a lot higher ISO or faster lenses.  Household light is pretty dark for a DSLR; stage lighting or adding flash are the two situations where I get proper exposure.
What is the historgram saying for these shots?

The leaves in the waterfall shot look good, so there is hope. Yes I wanted you to jack the ISO up for faster shutter speeds. Need to eliminate any user issues as well as things like a UV filter before pointing a finger. You may want to read up on what others are saying here plus check their samples.


You may also want to try out DOFMaster just to see how shallow the DOF is in the shots your comparing. If you're shooting wide open or near wide open the DOF can be very shallow when the camera to subject distance is close.

"A skill is developed through constant practice with a passion to improve, not bought."

Thanks for reminding me of the 1/focal length rule. I'd totally forgotten about that. I agree that some of the issues with those shots could be hand shake.

With film, ISO 400 film was about the highest you could go before you got a lot of noise so I had been keeping the ISO setings lower on this camera. I realize that you can go a lot higher with digital so I reset the auto high setting to 25600 so I could get some faster shutter speeds.

Results are below. They're still a bit mixed in my opinion. I shot them all above the 1/focal length  rule and some 2x or 3x or more above that, so in theory that would eliminate the camera shake issue.

I went outside and shot 100+ photos about an hour before sunset. The ones in sunlight seemed bettter if there was a decent amount of contrast, but even in good light, if there was not much contrast (e.g. tree bark, green leaves, etc.) then the results were still not sharp and clear.

BTW I got the 70-300mm f/4-5.6 IS USM today so some of the shots below are with it. The rest are with the 24-105 f4 L. All are large fine jpegs straight from the camera, blown up to 100%.

santa1 Indoors daylight, no interior lights on, 24mm focal length, 1/30, ISO 1000


santa2 Indoors daylight, with interior lights on, 105mm focal length, 1/125, ISO 6400



santa3 Indoors daylight, with interior lights on, 300mm focal length, 1/320, ISO 10000



santa4 Indoors daylight, with interior lights on, 300mm focal length, 1/640, ISO 20000



wall1 outdoors, 105mm focal length, 1/500, ISO 100



wall2 outdoors, 270mm focal length, 1/500, ISO 100



treebark1 outdoors, 70mm focal length, 1/125, ISO 25600



street1 outdoors, 24mm focal length, 1/80, ISO 100

[Moderator removed image due to containing private/personal information]


treebark2 outdoors, 300mm focal length, 1/320, ISO 25600



license1 outdoors, 300mm focal length, 1/320, ISO 25600



leaves1 outdoors, 70mm focal length, 1/320, ISO 25600



leaves2 outdoors, 300mm focal length, 1/320, ISO 500



Most of them still don't seem that sharp to me. What do you guys think?
I checked out the links you posted (thanks) and most people are raving about how good the low light performance is on the 6d but I'm just not seeing it.

Here's a link to where someone compares a few different cameras one of them being the 6d. My images are not as sharp as them as far as I can tell. 

I'll try to post some shots to get some input. Not sure if it's better post to flickr and link to them or to inert them into the post. Will try to work on that later.

Yeah being even slightly out of focus seems to be the most likely reason that this scenario wouldn't work well. I'll play with it a bit once the camera arrives later this week and see how it goes.


Thanks for the rental tips. I knew about borrowlenses but not the other two. They really have some pretty decent rates. Probably a good idea to rent a lens anyway to see how you like it before you buy it.

Rising Star

Congrats on your 6D! 


To give a short answer, of course cropping in isn't ideal, but for small prints it'll work.  If you know you'll be working a lot at longer focal lengths anyway, it makes sense to eventually get a lens that suits that. 


As for L vs non-L, there's no sweeping answer: you have to find the best balance between what your budget allows for you to get, and the benefits/drawbacks of each lens that is in consideration.  A really thoughtful guide is the first post here:  (not this forum, but there are some really great content already out there from eloquent people, so it doesn't make sense to repeat or copy it).

JFO--thanks. I'll eventually get a longer lens I'm sure, just trying not to blow up my finances at this time with the new camera/lens, Christmas spending, and 2 weeks upcoming in Japan---trying not to spend too much more if I can help it!.


Thanks for that link I'll take a look. I know there are no definitive answers, so I'm just looking for input. I'll have my 6d and lens in a few days and will start playing with it then I'll know more about how it works. Trying to think about it and research before I run out of time and leave on my trip in case I do decide to get a longer lens before I go.   Thanks again!

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