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Messages - jd7

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1
Lenses / Re: Canon 24-70 f/4L IS disappointing?
« on: July 21, 2014, 07:31:00 AM »
Thanks for adding your thoughts Sporgon.  If you're happy with your 24-70 4 IS at 50mm f/4, I'm sure it's more than good enough for me ... which further convinces me I really do have a sub-standard copy.

I've also done some more testing over the last couple of days.  I haven't done it very scientifically (eg shooting hand-held, although making sure the shutter time is nice and fast) but it's consistent over a variety of subjects/situations.  Taking the same subject at different focal lengths, I'm happy with the lens at f/4 at 24 and 70, but at 50 it's just plain poor.   I have to say I generally like the handling of the lens, so if it was (pretty much) as sharp at 50 as it is at 70, I'd be very happy with it.

Called the shop today and they just say they'll send it back to Canon ... and I should get it back in 4 to 6 weeks.  Sigh.  Fingers crossed it doesn't actually take that long ... and they actually fix it.


2
Reviews / Re: Please help me love ef 35mm f2 IS vs 40mm pancake
« on: July 21, 2014, 07:06:17 AM »
I have both the 35 IS and the 40, and I have to say the 35 IS has grown on me the more I've used it.

This was my thinking a while ago (from a post of mine earlier in the year - sorry it's a bit of a long ramble, but saved me some typing now  :) ):
- my feeling is the 35IS is a little sharper, but there's not a whole lot in it
- my feeling is the 35IS has slightly better colour and contrast, but there's not a lot in it
- my thinking is the 35IS has slightly nicer bokeh, but there's not a whole lot in it
- the 35IS has noticeably faster and quieter AF - but that's not to say the pancake is bad in those respects, so query how much difference this is likely to make in practice (no doubt it depends in large part on what you're shooting)
- the 35IS feels more substantial and hence makes you think it may have better build quality - but I have no idea whether, in reality, the 35IS is likely to be any more durable.  (In this case I strongly suspect it is likely to be more durable than the pancake, but all the same I get sick of reading lens reviews which seem to equate weight with build quality, and conclude anything light weight is lesser quality.  Isn't that like saying something made of steel is always a higher build quality than something made of titanium or carbon fibre?)
- of course, the 35IS has a one stop aperture advantage (which you'd rather have than not), and IS (worth at least another 3 stops - which allows you the choice of longer shutter times or lower ISO)
- the 35IS has 67 filter thread, which means you may already have filters you can use on it (unlikely with the pancake)
- the extra 5 mm of width (in the focal length) is noticeable on the 35IS but again, it's not very different - and to the extent there is a difference, each has its pros and cons
- much better focus ring

Weighed against that, the 35IS is around 3x more expensive than the pancake, substantially larger and over 2.5x heavier (even if it still ranks as a relatively small and light lens in the bigger scheme of things).

For all that though, the more I've used the 35IS the more I like it over the 40mm.  I like the slightly wider FOV, the slicker AF, the IS for low light, f/2 for low light and blurring backgrounds (well, it's a 35mm lens so I don't expect miracles ), the manual focus ring, ....  In the end all the little things add up.  I think the 40mm is a great little lens and I can understand why you're happy with it - and it's very hard to go past for the money - but if I could only keep one I'd keep the 35IS.  It's just a bit more versatile.

By the way, my 35IS is pretty sharp even at f/2.  If yours isn't, I'd say you either need AFMA or there's something wrong with it.


3
Lenses / Re: Canon 24-70 f/4L IS disappointing?
« on: July 19, 2014, 08:10:04 PM »
Thanks for your thoughts all.

To those recommending the 24-70 2.8L II, I have no doubt it's superb.  I'm looking for a general purpose "walk around" / travel / hiking lens, so the combination of heavier weight, larger size and higher price mean it's not perfect for my needs.  Obviously having 2.8 would be nice at times, but I don't think that's so important to me for what I plan to use this lens for.  And if I need to stop action in low light, I have primes in the same focal length range.

Reading around the internet (again!) makes me think I may just have a poor copy of the 24-70 4L IS.  TDP and LensRentals note the drop in sharpness at 50mm but seem to suggest it's not too bad.  SLRLounge has a "shoot out" of a number of lenses at 24, 35, 50 and 70 mm and rates the lens pretty highly - and their 100% crops seem to back up the idea.  Various other reviews (Photozone, Bob Atkins, PhotographyBlog, to name a few) seem similarly impressed with the lens at all focal lengths.  Interestingly, SLRgear notes they tested 3 copies and the first two were very poor at 50mm but the third one was significantly better (albeit 50mm remained a weak spot).  It all makes me think I'm right to be expecting better than I'm seeing from my lens.

In any event, I will call the shop and see what they say but I'll be surprised if they'll do anything more than send it off to Canon to be checked.  Sadly I'm outside the 14 day period within which they will exchange for another product, and they do not offer refunds unless the item doesn't work (and I'm guessing I'll have trouble convincing them about that).  Unfortunately shops in Australia rarely offer the kind of "no questions asked" refund policies which I gather can be found overseas (or at least in the US).

Hhmmm, maybe I should take mrsphotografie's hint and ditch the 24-70 zoom altogether and just go with primes.

4
Lenses / Canon 24-70 f/4L IS disappointing?
« on: July 18, 2014, 10:21:13 PM »
Hi all

I've been playing with a Canon 24-70 4L IS for the last few weeks and comparing it to my old Sigma 24-70 2.8 EX DG HSM.  I haven't had that much time to do comparisons but so far I'm struggling to be impressed by the 24-70 4L IS.   I was hoping - expecting really - it would be a clear step up from the Sigma, but it's closer than that.  I know I'm pixel peeping but still, U have to say I was expecting more from a Canon L (especially after lenses like the 70-200 2.8 IS II, and non-L lenses like the 35 2 IS). 

Trying to sum it up:

At f/2.8 the Sigma is pretty good at 24mm, but it gets steadily worse as the focal length increases.  The drop off in sharpness and contrast by 70mm is significant.

At f/4, the Sigma shows a clear improvement over 2.8 across the whole focal length range.  The quality still drops as the focal length increases but the drop off is less significant than at 2.8.

At f/4, the Canon is good at 24mm, but by 35mm the quality has dropped noticeably.  By 50mm I'd go so far as to call it poor - certainly for sharpness, if not so much for contrast.  It improves again by 70mm, but it doesn't get back to the standard it set at 24mm.  I would say the Sigma wins at f/4 at 50mm and perhaps even 35mm.

From various reviews, I expected the Canon to be weaker towards the middle of its range, but looking at the LensRentals' resolution tests I thought it would still be pretty decent there.  What has surprised me is just how poor it seems towards the middle of its focal length range.   I think I'm still leaning towards keeping the Canon and selling the Sigma - because the Canon's IS has its uses, it's a bit lighter, it's better at 24mm and 70mm, and it's got its semi-macro mode for a bit of fun.  That said, the Sigma's f/2.8 has its uses too - even if the quality drops towards the longer end of the focal length range - and I'd get more if sold the Canon.

Anyone else really disappointed with the 24-70 4L IS in the middle of its focal length range?  For those who are happy with their 4L ISs, are you genuinely happy with them at 50mm?  Have I got a poor copy?  Hhmmm, I don't want to pay for the Canon 24-70 2.8L II and I'm uncertain about the Tamron 2.8 VC (my brother has one).  Maybe I should just keep my Sigma?  Or look for a 2nd-hand 24-105 4L IS?

Thanks for any thoughts.


5
Canon General / Re: What's Would You Keep? [The anti-G.A.S. thread]
« on: July 16, 2014, 06:26:56 AM »
About 18 months ago I decided to try to rationalise my gear ... and in that time my kit has grown by two lenses  ???  I guess you could say that didn't go well!

Of my current gear the first off would be my 50 1.4.  It's nice to have a 1.4 lens in my kit but the reality is I don't use it that much.  The next off would be the 40 2.8.  I really do like it for its size, but it's a nice little convenience I could manage without.  After that, it gets harder!  Although since photography is only a hobby for me, the truth is this gear is all an indulgence.

Anyway, if I had to ...
6D + 70-200 2.8 II
6D + 70-200 2.8 II + 35 2 IS
6D + 70-200 2.8 II + 35 2 IS + 430EX
6D + 70-200 2.8 II + 35 2 IS + 430EX + 24-70 4 IS.

That said, I wonder if the 70-200 4 IS might be a better choice for me than the 70-200 2.8 II.  The comparative portability of the 70-200 4 IS makes it very useful to me!


6
Lenses / Re: Best short telephoto?
« on: July 05, 2014, 08:53:05 AM »

The problem is that sporting events usually need a fast shutter speed, and the light is not all that bright.  Combine that with the poor low light performance of APS-C, and its poor for that use.
A FF body with at least a f/4 lens is head and shoulders better.
A Canon 135mm f/2L might be a good choice for a crop or FF.


Agreed - if low light is an issue then going with a FF body is the way to go.  I just thought I'd mention the EF-S 55-250 as food for thought, as the OP hasn't said what the lighting conditions are likely to be.  For example it's if it's an open air stadium and the players will be in bright sunlight, the 55-250 might work.  I took some photos at the Australian Open tennis in January and the conditions were exactly like that.  I was shooting with a 6D and an f/4 lens, but from the lighting point of view a crop body and the 55-250 would have been fine.


7
Lenses / Re: Best short telephoto?
« on: July 04, 2014, 07:09:13 AM »
If you have (or can get hold of) an APS-C camera, how about the EF-S 55-250 IS STM?  According to TDP it's 4.4" long (http://www.the-digital-picture.com/Reviews/Canon-EF-S-55-250mm-f-4-5.6-IS-STM-Lens.aspx), and allowing for the crop factor it gives a 400mm equivalent FOV.   My Dad has one and I think it's fantastic when you consider it's size, weight and cost.  It may not be an L, but if I was still shooting with a crop DSLR I reckon I'd pick one up, notwithstanding the relatively slow aperture.

From what it says in the TDP review it seemer the newer STM version is a definite step up from the previous models.

8
Lenses / Re: What was your first L lens?
« on: June 06, 2014, 10:15:58 PM »
70-200 f/2.8L IS (mk 1) about 9 years ago.  It's still going strong! 

I have largely managed to (just!!) resist the temptation to get lots of L lenses (well, financial considerations also help with the "resistance"!).  I ran with a few Sigma lenses for a while because they seemed to offer good value, although since moving to full frame I've been re-jigging my lens collection and ended up swinging back towards Canon - although still not many Ls.  As fantastic as the Ls (generally) are they tend to be expensive, heavy and big and I've discovered that for my shooting I simply make more use out of lenses which are smaller and lighter.  Am currently evaluating a 24-70 f/4L IS as a possible replacement for my Sigma 24-70 f/2.8 EX HSM, in part because the Canon is lighter (the size is actually pretty similar) and because I like the idea of the semi-macro mode, but I'm still testing it out.

9
Quote

I'll be the first to admit the 6D's AF is not nearly as good as the 5D3 or 1Dx, but it's not bad either.  Unless you are shooting lots of sports or fast paced wildlife (BIF), the 6D's AF is probably good enough for most uses including weddings.

+1

10
Lenses / Re: Canon 24-70 f/4L IS - macro mode any good?
« on: May 08, 2014, 06:03:16 AM »
I just don't know what to make of the focus shift issue.  Looking around the internet, some people says it's a big problem, others say it's there but in practice it's not a big deal, and others say the lens is just fine ...

Anyway, I looked at one this evening and compared it to the Sigma 24-70 2.8 EX HSM which I currently own. The lenses are actually pretty close in size (the Sigma is a fraction longer and a bit fatter), and even the weight difference felt less noticeable than I'd expected.  Hhhmmm.

11
Lenses / Re: Canon 24-70 f/4L IS - macro mode any good?
« on: May 06, 2014, 01:48:59 AM »
The macro mode is useful for my usage. This lens is my one lens solution for travel and hiking. The short MFD is a problem, it will block the light in some angle, but this is not huge problem, changing position will overcome this problem. Even my 100L also will block light if I use hood at some position. The IS is silent and effective than my 100L. If you need a decent zoom with close focus ability, this lens is the only choice in the market.

Glad to hear you're finding it a good solution for travel and hiking!  Sounds like your usage is similar to what I have in mind, so if you're finding the macro mode useful, it sounds like it would probably work well for me too.  Thanks for your thoughts.

12
Lenses / Re: Canon 24-70 f/4L IS - macro mode any good?
« on: May 06, 2014, 01:46:51 AM »
The tests I read, showed that 24-70 F4 IS suffers from the problem of "shift focus". When closing the diaphragm, the focus shifts slightly. This makes it difficult to do macro shots with aperture between F4.5 and F11. However, in live view this problem does not happen.

I've seen a few reviews saying that too.  The Photozone review is one example, but I see it now has a note which raises the possibility they had a bad copy and it got repaired ... although it seems they didn't get to try it out after repair for themselves, so not sure what to make of it.

Also, is focus shift common with macro lenses?  The one time I got to play with a 100L macro I didn't notice it ... but I'm sure I've read claims on the internet (must be true, right?!) that it's quite common.  Maybe the out of focus shots I took with the 100L weren't my fault after all?!  :D

Anyway, if it's not a problem if you use live view, that probably provides a work around for the sort of macro shots I expect I'd be taking.  Doesn't sound ideal though.

13
Lenses / Canon 24-70 f/4L IS - macro mode any good?
« on: May 04, 2014, 09:12:30 PM »
To all those who have experience with the 24-70 F/4L's macro mode - do you find it's useful or is it just a gimmick?  From what I've read the working distance is really short - about 3 cm!!  That's going to pretty much rule out using it for insects and anything else which can run/fly away (not to mention sting or bite you!), but what about for things which can't/don't run away?  Is the macro mode useful in practice for those things, or is the working distance so short you end up blocking all the light or running into other problems?

I quite like the idea of the 24-70 F/4L as a relatively light travel and hiking lens, but it's certainly not cheap.  If it doubles as a decent macro lens too though (even though it's only 0.7 magnification), it might be the thing which makes me take the plunge (subject to selling my Sigma 24-70 2.8).

Thanks for any thoughts you can provide.

14
EOS Bodies / Re: 1d IV vs. 7D II
« on: April 23, 2014, 10:00:03 PM »


There have been strides in sensor technology, however pixel size still dominates the determination of how much noise you have. Smaller pixels will always have more noise, that's a simple matter of physics. We have improved READ noise with better sensor technology, but read noise is only a small contribution to total noise (especially at high ISO)...photon shot noise is the primary source of noise in images. The larger pixels of the 1D IV will always win out against smaller pixels of APS-C sensors. The only way the 7D II could do better is if it had larger pixels than the 1D IV, however that would make it something like a 10mp sensor...highly unlikely.

A smaller pixel generates less read noise, correct. For example, the 7D has 8e- read noise, vs. the 1D X's 35e- read noise. But read noise is a tiny, tiny, tiny contributor to overall noise. The lower FWC means TOTAL noise (including photon shot noise) is higher, because your maximum signal (as dictated by that lower FWC) is lower.

The overall sensor area is what dictates total noise in the image, and in that respect it doesn't really matter what the pixel size is. Smaller sensors have more noise than larger sensors due to their smaller total area/less total light gathered.

Jrista, I'm a little confused by your two statements - which seem at odds with each other, unless I misunderstand them. 

My understanding is noise is determined by the total light gathered by the system, and that is a function of the sensor's area and its quantum efficiency.  That would mean changing the 7D sensor for one which is the same size but has a smaller number of much larger pixels (which otherwise performed the same) wouldn't help with noise, because you wouldn't change the total light gathered by the system.  Larger pixels would presumably have a larger FWC, which might enable more subtle colour/brightness gradation (and perhaps increase dynamic range?), but wouldn't actually reduce noise.

Am I missing something?

That is essentially correct. Pixel size doesn't matter much because you can always downsample, which is effectively the same as either binning or having larger pixels. Let's say you have a 32mp APS-C and a 8mp APS-C. Both sensors have a Q.E. of 50%. Neither sensor has an AA filter. These two sensors are a factor of four difference in pixel size...you can fit four of the 32mp sized pixels into one 8mp sized pixel. If you take the 32mp image and downsample it to 8mp (8000x4000 pixels downsampled to 4000x2000 pixels), the results are the same. The per-pixel noise of the 32mp image is higher, however once downsampled, basic averaging effectively nullifies the increase in noise, and largely nullifies the increase in detail, resulting in nearly the same detail and exactly the same noise as the 8mp sensor. The detail will be slightly higher as you started out with a finer level of detail, and the multi-sampling process of downsampling means that while you are concurrently averaging out noise, you are also compounding the quality of detail in each pixel.

Now, let's say the 8mp camera has 40% Q.E. and the 32mp camera has 80% Q.E. Now the 32mp camera only has noise that is 50% worse than the 8mp, rather than twice as bad. If you downsample the 32mp image to the same dimensions as the 8mp image, the downsampled 32mp image will have less noise and will show the same advantage in detail. It is highly unlikely we will ever see a consumer-grade sensor with 80% Q.E. I've only seen those levels in Grade 1 scientific sensors (the kinds of sensors you find in astrophotography cameras or the stuff they ship up to the Hubble.) We may see sensors with 65% Q.E. or so, however that is only about a half-stop improvement over the ~50% most current sensors have now.

Now, let's say we have two sensors of differing size. Let's say we have a 16mp mp FF sensor, and an 8mp 24x16mm sensor (exactly half the area of the FF sensor, slightly larger than APS-C). Both cameras have exactly the same pixel size. If you frame your subject in one vertical half of the FF sensor with the camera oriented vertically, and crop out the other half, you will have identical results to the 8mp APS-C sensor. If you frame the same subject horizontally using the full area of the FF sensor, you are putting twice as much sensor area on the subject. You have gathered double the amount of light with the FF sensor as you are with the APS-C sensor...and it has nothing to do with pixel size. If you downsample the FF image to the same dimensions as the APS-C image, your going to trounce it in both noise levels and detail levels.

The total amount of light gathered is really what matters. Assuming the same sensor size, then the actual pixel size does not really matter all that much. There are things that may result in improved performance of one sensor with one pixels size or another. Improved quantum efficiency is one way. There are also caveats with pixel size. If you want more pixels, that also means more wiring. In FSI sensors, the increased wiring with smaller pixels means there is even less total light sensitive area than with larger pixels. Theoretically, assuming an identical fabrication process is used, our 8mp camera from above will actually have more total photodiode (light sensitive) area than the 32mp sensor. If they both have the same Q.E. then the 8mp sensor will actually perform slightly better due to the slightly greater total photodiode area. This would be the only way I think a 7D II could perform as well as or better (highly unlikely) than the 1D IV. By reducing pixel count significantly, one can increase the total amount of light-sensitive sensor area. I'm not exactly sure where the cutoff point would be...however you would have to pretty drastically reduce the wiring area of the 7D II. You would probably also need to use a process shrink (500nm to 180nm). Another way to do it would be to move to a BSI design. (This all assumes that there is enough wiring in the 1D IV sensor that total light sensitive area is still not greater than the area of an APS-C sensor...if it is, then actually there wouldn't be any way the 7D II could actually perform better.)

In this respect, you are indeed correct about color fidelity and dynamic range...larger pixels do have an edge here. However you are still going to find that greater total sensor area still has a greater impact on those aspects of IQ than larger pixels do in the long run (for example, the D800 has phenomenal color fidelity, however it's pixel size is only marginally larger than the 7D, which has pretty terrible color fidelity in the grand scheme of things...the greater total light gathering capacity, benefited by both higher Q.E. and being FF, of the D800 is it's real edge here.)

Other technology may be employed to increase the total light sensitivity of a sensor pixel. Currently sensors are effectively two dimensional...the only thing that really matters for total charge capacity is the area of the photodiode. Foveon-type sensors stack photodiodes, resulting in an increase in total charge capacity for each pixel. The same technique could theoretically be employed for monochrome and bayer sensors. Blue pixels would be least sensitive, as silicon will filter out most of the bluer wavelengths before they penetrate deeply. Green and red pixels would be most sensitive, allowing for two or three, maybe even four layers of photodiodes. Such technology could be employed in higher megapixel sensors to increase FWC and sensitivity. There is nothing that says the same techniques couldn't be employed with larger pixel sensors, though.

thanks for the explanatation jrista!

15
EOS Bodies / Re: 1d IV vs. 7D II
« on: April 23, 2014, 05:17:46 AM »


There have been strides in sensor technology, however pixel size still dominates the determination of how much noise you have. Smaller pixels will always have more noise, that's a simple matter of physics. We have improved READ noise with better sensor technology, but read noise is only a small contribution to total noise (especially at high ISO)...photon shot noise is the primary source of noise in images. The larger pixels of the 1D IV will always win out against smaller pixels of APS-C sensors. The only way the 7D II could do better is if it had larger pixels than the 1D IV, however that would make it something like a 10mp sensor...highly unlikely.

A smaller pixel generates less read noise, correct. For example, the 7D has 8e- read noise, vs. the 1D X's 35e- read noise. But read noise is a tiny, tiny, tiny contributor to overall noise. The lower FWC means TOTAL noise (including photon shot noise) is higher, because your maximum signal (as dictated by that lower FWC) is lower.

The overall sensor area is what dictates total noise in the image, and in that respect it doesn't really matter what the pixel size is. Smaller sensors have more noise than larger sensors due to their smaller total area/less total light gathered.

Jrista, I'm a little confused by your two statements - which seem at odds with each other, unless I misunderstand them. 

My understanding is noise is determined by the total light gathered by the system, and that is a function of the sensor's area and its quantum efficiency.  That would mean changing the 7D sensor for one which is the same size but has a smaller number of much larger pixels (which otherwise performed the same) wouldn't help with noise, because you wouldn't change the total light gathered by the system.  Larger pixels would presumably have a larger FWC, which might enable more subtle colour/brightness gradation (and perhaps increase dynamic range?), but wouldn't actually reduce noise.

Am I missing something?

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