Rishi and Everyone, Sorry Not A Cyclist, Large Images

Started Jul 7, 2016 | Discussions thread
Rishi Sanyal
Rishi Sanyal dpreview Admin • Posts: 850
Re: Rishi and Everyone, Sorry Not A Cyclist, Large Images

MightyMike wrote:

Alright so in short notice this is what I put together, I've been very busy today, haven't had a moment to pause but while out I got this sequence. Sorry its not in triplicate either.

I never promised perfection, nor did I say it was as good as other brands, all I'm suggesting is that its better than the DPR results show.

I used the Sigma 100-300mm F4.0 EX DG on the K-1, I used SEL-33, I initially took a few photos without the intent to do a burst AF-tracking test then decided to do one so refocused and started the sequence, the original few photos were not included. In SEL-33 like in any SEL mode one has to focus on the desired subject and acquire lock before bursting to obtain best results, that subject also has to stay inside the active focus point zone during the burst or you're guaranteed the camera will likely lose focus and likely won't re-obtain focus without the users intervention. I set my AF hold to medium, I usually use low and have tried high on occasion and if the action is very erratic but the subject is against a nothing background I'll consider turning AF hold off. These were done handheld however I didn't keep the initial focus target in the center of the frame nor did I zoom out which is something I'd normally do. These were shot at 300mm and F5.6 I'd suggest the subject was moving faster than the cyclist and based on head sizes is likely of a similar magnification, yes 300mm F5.6 affords me a little more forgiveness than 200mm F2.8 but only by less than a stop of DOF. I have to apologize as the subject isn't moving perfectly 100% directly at the camera, however I would like to suggest its close enough.

Here are the 15 original files, edited in an old version of ACR (5.7), ACR's sharpening and NR were whatever the default is, I've really never bothered to adjust it. I didn't use any camera profiles either. Its taken over 45 minutes to upload all these files, from ACR to photoshop to save no alterations passed ACR. The files are 18-21mb each


Here is a string of 1:1 crops (1200x800 each) centered on the persons head, no sharpening, no resizing (View original as always)

[9.7mb] http://www.michaelfastphotography.com/galleries/k-1/aftest/afcrops.jpg

Here is the scene for the purpose of showing how the subject moved around the frame during the sequence, these are obviously resized and sharpened so don't make any conclusions about the AF or DOF as at this size such failings are minimized and therefore not accurate. I repeat this is only to demonstrate how the subject move around the frame.

[13.7mb] http://www.michaelfastphotography.com/galleries/k-1/aftest/afscenes.jpg

Now I'm sure someone can tell me what I did wrong and I'm sure you all can figure out how many are in focus and how many aren't, I'll give you a hint, its better than 15%. Perhaps in the near future someone including myself could put together a more similar test to the DPR test but until then enjoy at least something that resembles their AF test.

First of all, thanks for doing this. I like how you've made it easy for us to see the results by compiling crops in addition to providing full-resolution images. That's exactly how it should be done.

Second, calm down, as I've suggested to you below. You are one of hundreds of commenters and thousands of comments that we cannot personally sift through every day, especially when doing so constitutes less than 1% of my job duties/description. In fact, many of us sacrifice our personal time and/or sleep to respond to you. We're human, and the last thing we want to see - when we're sacrificing our own sleep to respond to often petulant comments resulting from not even reading the reviews we work hard on - is someone attacking our integrity because we haven't responded to one out of many hundreds of comments/threads by 8am the morning after a comment was posted. You know, before the work day has even started. Oh - and when you posted your comment at 10pm last night? I was editing the Fujifilm launch content.

Seriously - and I say this with all due respect, but - get a grip. Exclaiming 'what integrity!' because I haven't personally responded to your post within hours of posting (and minutes of me waking up, as it were) only speaks to your hostility and false assumptions surrounding our intent, dedication, and honesty.

Now, to address your test: I see nothing that disagrees with anything we've written. You have about a 66% hit-rate in your example (5 out of 15 shots aren't perfectly focused). And that's for an example where:

1. The subject was so large as to cover nearly the entire AF grid for most of the sequence. It doesn't matter what AF point the camera used - most covered the subject. That doesn't at all stress subject tracking as our test does. Therefore, I'm not at all surprised that your hit-rate is higher than ours. What else would the camera have focused on when your boat is covering the entire AF area?

2. Which brings us to: 'well, then, at least the camera did keep up with the boat, didn't it, despite significant movement?' I'm glad you asked. The subject isn't changing distance relative to the camera as much as in our test. Why? Two reasons: (1) it's not straight on, there's a good deal of lateral movement, which itself requires no refocusing; and (2) a common misconception is that it's distance moved that matters, when it's actually change in relative distance to the camera that is most difficult, as the greater the change in relative distance, the more the focus element needs to move, and the larger the changes in measured phase difference - which taxes both the lens focus motor as well as the PDAF system. That's why a moving/erratic toddler shot close up at 35/1.4 is often the most challenging AF test (AF acquisition speeds for sports photography notwithstanding).

3. As you've already said, you also have more DOF to work with. Due both to a smaller aperture, as well as an object that is farther away.

Meanwhile, others who've repeated our test with a cyclist, a toddler, or a pet, see similar hit rates to ours, which you can see here, here, and here, and in private messages I obviously can't share.


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Rishi Sanyal, Ph.D
Deputy Editor, Technical Editor | Digital Photography Review
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