Rishi and Everyone, Sorry Not A Cyclist, Large Images

Started Jul 7, 2016 | Discussions thread
OP MightyMike Forum Pro • Posts: 39,130
Re: Rishi and Everyone, Sorry Not A Cyclist, Large Images
1

Rishi Sanyal wrote:

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.

I said some stupid things, it happens, I'll try to be more patient in the future, i'm sure you'll see what i wrote to your comments on that matter in your previous posting

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?

at 100% i wouldn't call the boat the subject, to be picky most of it is out of focus. In this SEL-33 mode the camera does not use any of the other points to obtain focus until focus lock is achieved, using this mode for a bird in flight sucks. If you can't keep that center point perfectly on the bird it won't lock focus, it will either hunt or choose the clouds near infinity. I'm not sure you have EXIF software that shows the point or points there were active, I certainly don't but when reviewing the photos in the camera it does show this, I haven't bothered to put the photos back on a card to review them in the camera so i can't give you a clear picture of what was happening. Had i used Auto-33 then yes the whole subject could be the boat and so long as any part of that subject was in focus then it was working.

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).

I agree about the toddler, however I apologize I never downloaded the reviews original 100% files the question I have if the change in the size of the person head should be enough to determine the amount of subject movement on the z-axis, if the heads start at a similar size and end at a similar size then wouldn't the relative distance to subject and amount of movement be the same? Further away is compensated for by the longer focal length. so what is the difference in relative head size? can someone check this out, It doesn't need to be you Rishi, I'm sure anyone on the forum can show, Maybe i misjudged the relative size of the head but it seemed similar to what i remember.

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.

I said above further away should have been completely compensated for by the extra focal length. Try to track a toddler with a 500mm lens near its MFD, maybe the other systems can do it but Pentax likely can't. the longer the focal length and the closer the subject the harder it is for AF to track. I won't even try swallows in flight with my Sigma 500mm F4.5 even though it just fine for airshows and other further BIFs and other animals. I probably wouldn't use it for sports either unless i was very far from the action.

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.

They're offering worse evidence then you blasted me for when i posted my galleries, mere comments, no proof, no explanation of lens focal length conditions. I don't distrust them I just want more evidence before i call their results valid.

I'm sure in time we'll see a bunch of similar to DPR's tests posted on the forum and i'm sure that we'll have results ranging from DPRs to closer to what i expect. And I'm sure averaged out its probably somewhere in the middle

-Rishi

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Rishi Sanyal, Ph.D
Deputy Editor, Technical Editor | Digital Photography Review
dpreview.com (work) | rishi.photography (personal)

Just before i hit post i went to the review, the initial head size is identical... assuming no zika virus their head should be similar in size at the same distance in real life. Yours was shot at 200mm, mine at 300mm so my guy was but a mere 50% further away. by the last frame your guys head took up about 1/5th the area of my guys head 44.7% mono-dimensionally 67% taking into account the focal length difference which would suggest my guy was 50% closer at the end of the sequence. My guy in the boat traveled 2.25x further in the same amount of time, started from further away and finished closer.

Unless my assumptions about similar head size are wrong then I actually had more Z-axis movement both relative and exact. The key telling point in this example is the the similar head size thus similar difficulty level

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Mike from Canada
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